Heterocyclic compounds and their use

Abstract

The present invention relates to therapeutically active azabicyclic compounds of formula (1), wherein Z1 is oxygen or sulphur, a method of preparing the same and to pharmaceutical compositions comprising the compounds. The novel compounds are useful as stimulants of the cognitive function of forebrain and hippocampus of mammals and especially in the treatment of Alzheimer's disease, severe painful conditions and glaucoma. ##STR1##

Description

The present invention relates to therapeutically active azacyclic compounds, a method of preparing the same and to pharmaceutical compositions comprising the compounds.

The novel compounds are useful as stimulants of the cognitive function of the forebrain and hippocampus of mammals and especially in the treatment of Alzheimer's disease.

Due to the in general improved health situation in the western world, elderly-related diseases are much more common now than in the past and are likely to be even more common in the future.

One of the elderly-related symptoms is a reduction of the cognitive functions. This symptom is especially pronounced in the pathophysiological disease known as Alzheimer's disease. This disease is combined with, and also most likely caused by, a up to 90% degeneration of the muscarinic cholinergic neurons in nucleus basalis, which is part of substantia innominata. These neurons project to the prefrontal cortex and hippocampus and have a general stimulatory effect on the cognitive functions of the forebrain as well as of hippocampus, namely learning, association, consolidation and recognition.

It is a characteristic of Alzheimer's disease that although the cholinergic neurons degenerate, then the postsynaptic muscarinic receptors in the forebrain and hippocampus still exist. Therefore muscarinic cholinergic agonists are useful in the treatment of Alzheimer's disease and in improving the cognitive functions of elderly people.

It is well known that arecoline (methyl 1-methyl-1,2,5,6-tetrahydropyridine-3-carboxylate) is such a cholinergic agonist.

Arecoline however has a very short biological half life and a small separation between central and peripheral muscarinic effects. Furthermore arecoline is a rather toxic compound.

EP-A-0307142 discloses a class of thiadiazoles, substituted on one of the ring carbon atoms with a non-aromatic azacyclic or azabicyclic ring system, and substituted on the other ring carbon atom with a substituent of low lipophilicity, or a hydrocarbon substituent, which are muscarinic agonists and therefore useful in the treatment of neurological and mental illnesses and severe painful conditions.

It is an object of the invention to provide new muscarinic cholinergic compounds.

The novel compounds of the invention are heterocyclic compounds having the formula I ##STR2## wherein

Z.sup.1 is oxygen or sulphur;

R is hydrogen, halogen, amino, --NHCO--R.sup.2, C.sub.3-7 -cycloalkyl, C.sub.4-10 -(cycloalkylalkyl), --Z.sup.2 --C.sub.3-7 -cycloalkyl optionally substituted with C.sub.1-6 -alkyl, --Z.sup.2 --C.sub.4-10 -(cycloalkylalkyl), --Z.sup.2 --C.sub.4-10 -(cycloalkenylalkyl), --Z.sup.2 --C.sub.4-10 -(methylenecycloalkylalkyl), --NH--R.sup.2, --NR.sup.2 R.sup.3, --NH--OR.sup.2, phenyl, phenoxy, benzoyl, benzyloxycarbonyl, tetrahydronaphtyl, indenyl, X, R.sup.2, --Z.sup.2 R.sup.2, --SOR.sup.2, --SO.sub.2 R.sup.2, --Z.sup.2 --R.sup.2 --Z.sup.3 --R.sup.3, --Z.sup.2 --R.sup.2 --Z.sup.3 --R.sup.3 --Z.sup.4 --R.sup.4, --Z.sup.2 --R.sup.2 CO--R.sup.3, --Z.sup.2 --R.sup.2 --CO.sub.2 --R.sup.3, --Z.sup.2 --R.sup.2 --O.sub.2 --R.sup.3, --Z.sup.2 --R.sup.2 CONHR.sup.3, --Z.sup.2 --R.sup.2 --NHCOR.sup.3, --Z.sup.2 --R.sup.2 --X, --Z.sup.2 --R.sup.2 --Z.sup.3 --X, wherein Z.sup.2, Z.sup.3 and Z.sup.4 independently are oxygen or sulphur, and R.sup.2, R.sup.3 and R.sup.4 independently are straight or branched C.sub.1-15 -alkyl, straight or branched C.sub.2-15 -alkenyl, straight or branched C.sub.2-15 -alkynyl, each of which is optionally substituted with halogen(s), --OH, --CN, --CF.sub.3, --SH, --COOH, --NH--R.sup.2, --NR.sup.2 R.sup.3, C.sub.1-6 -alkyl ester, one or two phenyl, phenoxy, benzoyl or benzyloxycarbonyl wherein each aromatic group is optionally substituted with one or two halogen, --CN, C.sub.1-4 -alkyl or C.sub.1-4 -alkoxy, and X is a 5 or 6 membered heterocyclic group containing one to four N, O or S atom(s) or a combination thereof, which heterocyclic group is optionally substituted at carbon or nitrogen atom(s) with straight or branched C.sub.1-6 -alkyl, phenyl, benzyl or pyridine, or a carbon atom in the heterocyclic group together with an oxygen atom form a carbonyl group, or which heterocyclic group is optionally fused with a phenyl group; and

R.sup.5 and R.sup.6 may be present at any position, including the point of attachment of the thiadiazole or oxadiazole ring, and independently are hydrogen, straight or branched C.sub.1-5 -alkyl, straight or branched C.sub.2-5 -alkenyl, straight or branched C.sub.2-5 -alkynyl, straight or branched C.sub.1-10 -alkoxy, straight or branched C.sub.1-5 -alkyl substituted with --OH, --OH, halogen, --NH.sub.2 or carboxy; R.sup.1 is hydrogen, straight or branched C.sub.1-5 -alkyl, straight or branched C.sub.2-5 -alkenyl or straight or branched C.sub.2-5 -alkynyl; or

a pharmaceutically acceptable salt thereof.

Examples of such salts include inorganic and organic acid addition salts such as hydrochloride, hydrobromide, sulphate, phosphate, acetate, fumarate, maleate, citrate, lactate, tartrate, oxalate, or similar pharmaceutically acceptable inorganic or organic acid addition salt.

The compounds of this invention are also useful analgesic agents and therefore useful in the treatment of severe painful conditions.

Furthermore, the compounds of this invention are useful in the treatment of glaucoma.

The invention also relates to methods of preparing the above mentioned compounds, comprising:

a) alkylating a compound of formula II ##STR3## wherein Z.sup.1, R, R.sup.5 and R.sup.6 have the meanings defined above with an alkyl halide and reducing the compound thus formed with hydride ions to form a compound of formula I ##STR4## wherein Z.sup.1, R, R.sup.1, R.sup.5 and R.sup.6 have the meanings defined above, or

b) oxidizing a compound of formula III ##STR5## wherein Z.sup.1, R.sup.1, R.sup.2, R.sup.5 and R.sup.6 have the meanings defined above by standard procedures to form a compound of formula IV ##STR6## and subsequent displacement of --SO.sub.2 --R.sup.2 with an appropriate nucleophile to form a compound of formula I.

It is to be understood that the invention extends to each of the stereoisomeric forms of the compounds of formula I as well as the racemates.

The pharmacological properties of the compounds of the invention can be illustrated by determining their capability to inhibit the specific binding of .sup.3 H-Oxotremorine-M (.sup.3 H-Oxo). Birdsdall N. J. M., Hulme E. C., and Burgen A. S. V. (1980). "The Character of Muscarinic Receptors in Different Regions of the Rat Brain". Proc. Roy. Soc. London (Series B) 207,1.

.sup.3 H-Oxo labels muscarinic receptor in the CNS (with a preference for agonist domains of the receptors). Three different sites are labelled by .sup.3 H-Oxo. These sites have affinity of 1.8, 20 and 3000 nM, respectively. Using the present experimental conditions only the high and medium affinity sites are determined.

The inhibitory effects of compounds on .sup.3 H-Oxo binding reflects the affinity for muscarinic acetylcholine receptors.

All preparations are performed at 0.degree.-4.degree. C. unless otherwise indicated. Fresh cortex (0.1-1 g) from male Wistar rats (150-250 g) is homogenized for 5-10 s in 10 ml 20 mM Hepes pH: 7.4, with an Ultra-Turrax homogenizer. The homogenizer is rinsed with 10 ml of buffer and the combined suspension centrifuged for 15 min at 40,000.times.g. The pellet is washed three times with buffer. In each step the pellet is homogenized as before in 2.times.10 ml of buffer and centrifuged for 10 min at 40,000.times.g.

The final pellet is homogenized in 20 mM Hepes pH: 7.4 (100 ml per g of original tissue) and used for binding assay. Aliquots of 0.5 ml is added 25 .mu.l of test solution and 25 .mu.l of .sup.3 H-Oxotremorine (1.0 nM, final concentration) mixed and incubated for 30 min at 25.degree. C. Non-specific binding is determined in triplicate using arecoline (1 .mu.g/ml, final concentration) as the test substance. After incubation samples are added 5 ml of ice-cold buffer and poured directly onto Whatman GF/C glass fibre filters under suction and immediately washed 2 times with 5 ml of ice-cold buffer. The amount of radioactivity on the filters are determined by conventional liquid scintillation counting. Specific binding is total binding minus non specific binding.

Test substances are dissolved in 10 ml water (if necessary heated on a steam bath for less than 5 minutes) at a concentration of 2.2 mg/ml. 25-75% inhibition of specific binding must be obtained before calculation of IC.sub.50.

The test value will be given as IC.sub.50 (the concentration (ng/ml) of the test substance which inhibits the specific binding of .sup.3 H-Oxo by 50%). ##EQU1## where C.sub.o is specific binding in control assays and C.sub.X is the specific binding in the test assay. (The calculations assume normal mass-action kinetics).

Test results obtained by testing some compounds of the present invention will appear from the following table 1.

TABLE 1______________________________________ Inhibition in vitro OXO BINDINGCompound No. (ng/ml)______________________________________68 0.3969 0.4770 1.271 0.4372 0.5473 0.3374 1.175 0.4477 1.078 3.279 7.280 1481 1882 8.283 5.984 4.985 6.487 1.888 3.989 2.190 2.091 7.993 1094 595 1.696 3.097 5.498 4.399 0.62100 13101 1.6102 5.2103 6.4104 4.5105 20106 9.2107 2.1108 12110 285111 19112 10114 26116 2.1117 0.37118 0.47119 1.9120 3.8121 0.54122 16123 1.0124 1.0125 0.6126 3.9128 100129 5.4133 2.1134 0.30135 0.47136 0.43138 1.3139 0.92140 19141 2.1______________________________________

The compounds of the invention, together with a conventional adjuvant, carrier, or diluent, and if desired in the form of a pharmaceutically acceptable acid addition salt thereof, may be placed into the form of pharmaceutical compositions and unit dosages thereof, and in such form may be employed as solids, such as tablets or filled capsules, or liquids, such as solutions, suspensions, emulsions, elixirs, or capsules filled with the same, all for oral use, in the form of suppositories for rectal administration; or in the form of sterile injectable solutions for parenteral (including subcutaneous) use. Such pharmaceutical compositions and unit dosage forms thereof may comprise conventional ingredients in conventional proportions, with or without additional active compounds or principles, and such unit dosage forms may contain any suitable effective muscarinic cholinergic agonistic amount of the active ingredient commensurate with the intended daily dosage range to be employed. Tablets containing ten (10) milligrams of the active ingredient or, more broadly, one (1) to hundred (100) milligrams, per tablet, are accordingly suitable representative unit dosage forms.

The compounds of this invention can thus be used for the formulation of pharmaceutical preparations, e.g. for oral and parenteral administration to mammals including humans, in accordance with conventional methods of galenic pharmacy.

Conventional excipients are such pharmaceutically acceptable organic or inorganic carrier substances suitable for parenteral or enteral application which do not deleteriously react with the active compounds.

Examples of such carriers are water, salt solutions, alcohols, polyethylene glycols, polyhydroxyethoxylated castor oil, gelatine, lactose, amylose, magnesium stearate, talc, silicic acid, fatty acid monoglycerides and diglycerides, pentaerythritol fatty acid esters, hydroxymethyl cellulose and polyvinylpyrrolidone.

The pharmaceutical preparations can be sterilized and mixed, if desired, with auxiliary agents, emulsifiers, salt for influencing osmotic pressure, buffers and/or colouring substances and the like, which do not deleteriously react with the active compounds.

For parenteral application, particularly suitable are injectable solutions or suspensions, preferably aqueous solutions with the active compound dissolved in polyhydroxylated castor oil. Ampoules are convenient unit dosage forms. Tablets, dragees, or capsules having talc and/or a carbohydrate carrier or binder or the like, the carrier preferably being lactose and/or corn starch and/or potato starch, are particularly suitable for oral application. A syrup, elixir of the like can be used in cases where a sweetened vehicle can be employed.

Generally, the compounds of this invention are dispensed in unit form comprising 1-100 mg in a pharmaceutically acceptable carrier per unit dosage.

The dosage of the compounds according to this invention is 1-100 mg/day, preferably 10-70 mg/day, when administered to patients, e.g. humans, as a drug.

A typical tablet which may be prepared by conventional tabletting techniques contains:

______________________________________Active compound 5.0 mgLactosum 67.8 mg Ph.Eur.Avicel .RTM. 31.4 mgAmberlite .RTM. 1.0 mgMagnesii stearas 0.25 mg Ph.Eur.______________________________________

Due to the high muscarinic cholinergic receptor agonistic activity, the compounds of the invention are extremely useful in the treatment symptoms related to a reduction of the cognitive functions of the brain of mammals, when administered in an amount effective for stimulating the cognitive functions of the forebrain and hippocampus. The important stimulating activity of the compounds of the invention includes both activity against the pathophysiological disease, Alzheimer's disease as well as against normal degeneration of brain function. The compounds of the invention may accordingly be administered to a subject, e.g., a living animal body, including a human, in need of stimulation of the cognitive functions of the forebrain and hippocampus, and if desired in the form of a pharmaceutically acceptable acid addition salt thereof (such as the hydrobromide, hydrochloride, or sulfate, in any event prepared in the usual or conventional manner, e.g., evaporation to dryness of the free base in solution together with the acid), ordinarily concurrently, simultaneously, or together with a pharmaceutically acceptable carrier or diluent, especially and preferably in the form of a pharmaceutical composition thereof, whether by oral, rectal, or parenteral (including subcutaneous) route, in an effective forebrain and hippocampus stimulating amount, and in any event an amount which is effective for improving the cognitive function of mammals due to their muscarinic cholinergic receptor agonistic activity. Suitable dosage ranges are 1-100 milligrams daily, 10-100 milligrams daily, and especially 30-70 milligrams daily, depending as usual upon the exact mode of administration, form in which administered, the indication toward which the administration is directed, the subject involved and the body weight of the subject involved, and the preference and experience of the physician or veterinarian in charge.

The invention will now be described in further detail with reference to the following examples:

EXAMPLE 1

A. 3-(3-Chloro-1,2,5-thiadiazol-4-yl)pyridine

To a solution of sulfurmonochloride (2.4 ml, 30 mmol) in N,N-dimethyl-formamide (5 ml) was slowly added alpha-aminoalpha(3-pyridyl)acetonitrile (Archive der Pharmazie 289 (4) (1956)) (1.70 g, 10 mmol). The reaction mixture was stirred at room temperature for 18 h. Water (20 ml) was added and the aqueous phase was extracted with ether and the ether phase discharged. A 50% potassium hydroxide solution was added to the aqueous phase to pH>9. The aqueous phase was extracted several times with ether and the ether phases were dried and evaporated. The residue was purified by column chromatography (SiO.sub.2, eluent: ethyl acetate/methylene chloride (1:1)). The title compound was collected in 45% (880 mg) yield. M.sup.+ : 197.

B. 3-(3-Methoxy-1,2,5-thiadiazol-4-yl)pyridine

To a solution of sodium (460 mg, 20 mmol) in methanol (10 ml) was added 3-(3-chloro-1,2,5-thiadiazol-4-yl)pyridine (750 mg, 3.8 mmol). The mixture was stirred at 50.degree. C. for 1 h and evaporated. The residue was dissolved in water and extracted with methylene chloride. The combined organic phases were dried and evaporated to give the title compound, which crystallized with petroleum ether in a 630 mg (86%) yield.

C. 3-(3-Methoxy-1,2,5-thiadiazol-4-yl)-1 -methyl-pyridinium iodide

A mixture of methyl iodide (0.37 ml, 6 mmol) and 3-(3-methoxy-1,2,5-thiadiazol-4-yl)pyridine (500 mg, 2.5 mmol) in acetone (10 ml) was stirred at room temperature for 18 h. The title compound precipitated from the solution and was collected by filtration. Yield: 1.0 g (100%).

D. 1,2,5,6-Tetrahydro-3-(3-methoxy-1,2,5-thiadiazol-4-yl)-1-methylpyridine oxalate

Sodium borohydride (460 mg, 12 mmol) was added to a solution of 3-(3-methoxy-1,2,5-thiadiazol-4-yl)-1-methylpyridinium iodide (1.0 g, 3 mmol) in ethanol (99.9%, 20 ml) and the reaction mixture was stirred at room temperature for 1 h. After evaporation the residue was dissolved in water and extracted with methylene chloride. The dried organic phases were evaporated and the residue purified by column chromatography (SiO.sub.2, eluent: ethyl acetate/methanol (4:1)). The title compound was crystallized as the oxalate salt from acetone. Yield: 390 mg. (M.p. 150.degree. C.; M.sup.+ : 211; Compound 1).

EXAMPLE 2

A. 3-(3-Ethoxy-1,2,5-thiadiazol-4-yl)pyridine

To a solution of sodium (440 mg, 17 mmol) in ethanol (10 ml) was added 3-(3-chloro-1,2,5-thiadiazol-4-yl)pyridine (540 mg, 3.3 mmol). The mixture was stirred at 40.degree. C. for 10 h and evaporated. The residue was dissolved in water and extracted with methylene chloride. The combined organic phases were dried and evaporated to yield 520 mg (76%) of the title compound.

B. 3-(3-Ethoxy-1,2,5-thiadiazol-4-yl)-1-methylpyridinium iodide

A mixture of methyl iodide (0.3 ml, 5 mmol) and 3-(3-ethoxy-1,2,5-thiadiazol-4-yl)pyridine (520 mg, 2.5 mmol) in acetone (10 ml) was stirred at room temperature for 18 h. The title compound precipitated from the solution and was collected by filtration to yield 0.72 g (83%).

C. 3-(3-Ethoxy-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate

Sodium borohydride (300 mg, 8 mmol) was added to a solution of 3-(3-ethoxy-1,2,5-thiadiazol-4-yl)-1-methylpyridinium iodide (0.72 g, 2 mmol) in ethanol (99.9%, 20 ml) and the reaction mixture was stirred at room temperature for 1 h. After evaporation the residue was dissolved in water and extracted with methylene choride. The dried organic phases were evaporated and the residue purified by column chromatography (SiO.sub.2, eluent: ethyl acetate/methanol (4:1)). The title compound was crystallized as the oxalate salt from acetone, and recrystallized from methanol to yield 190 mg. (M.p. 137.degree. C.; M.sup.+ : 225; Compound 2).

EXAMPLE 3

A. 3-(3-Propoxy-1,2,5-thiadiazol-4-yl)pyridine

To a solution of sodium (440 mg, 17 mmol) in 1-propanol (10 ml) was added 3-(3-chloro-1,2,5-thiadiazol-4-yl)pyridine (650 mg, 3.3 mmol). The mixture was stirred at 50.degree. C. for 2 h and evaporated. The residue was dissolved in water and extracted with methylene chloride. The combined organic phases were dried and evaporated to yield 700 mg (96%) of the title compound.

B. 3-(3-Propoxy-1,2,5-thiadiazol-4-yl)-1-methylpyridinium iodide

A mixture of methyl iodide (0.37 ml, 6 mmol) and 3-(3-propoxy-1,2,5-thiadiazol-4-yl)pyridine (700 mg, 3.1 mmol) in acetone (10 ml) was stirred at room temperature for 18 h. The title compound precipitated from the solution and was collected by filtration to yield 0.98 g (88%).

C. 1,2,5,6-Tetrahydro-1-methyl-3-(3-propoxy-1,2,5-thiadiazol-4-yl)pyridine oxalate

Sodium borohydride (380 mg, 10 mmol) was added to a solution of 3-(3-propoxy-1,2,5-thiadiazol-4-yl)-1-methylpyridinium iodide (980 mg, 2.7 mmol) in ethanol (99.9%. 20 ml) and the reaction mixture was stirred at 0.degree. C. for 1 h. After evaporation the residue was dissolved in water and extracted with ethyl acetate. The dried organic phases were evaporated and the residue purified by column chromatography (SiO.sub.2 eluent: ethyl acetate/methanol (4:1)). The title compound was crystallized as the oxalate salt from acetone to yield 440 mg. (M.p. 148.degree. C.; M.sup.+ : 239; Compound 3).

EXAMPLE 4

A. 3-(3-Butoxy-1,2,5-thiadiazol-4-yl)pyridine

To a solution of sodium (290 mg, 12.5 mmol) in n-butanol (10 ml) was added 3-(3-chloro-1,2,5-thiadiazol-4-yl)pyridine (490 mg, 2.5 mmol). The mixture was stirred at 25.degree. C. for 18 h and evaporated. The residue was dissolved in water and extracted with methylene chloride. The combined organic phases were dried and evaporated to yield 580 mg (100%) of the title compound.

B. 3-(3-Butoxy-1,2,5-thiadiazol-4-yl)-1-methylpyridinium iodide

A mixture of methyl iodide (0.3 ml, 5 mmol) and 3-(3-butoxy-1,2,5-thiadiazol-4-yl)pyridine (580 mg, 2.5 mmol) in acetone (5 ml) was stirred at room temperature for 18 h. The title compound precipitated from the solution and was collected by filtration to yield 0.60 g (64%).

C. 3-(3-Butoxy-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate

Sodium borohydride (240 mg, 6.4 mmol) was added to a solution of 3-(3-butoxy-1,2,5-thiadiazol-4-yl)-1-methylpyridinium iodide (0.60 g, 1.6 mmol) in ethanol (99.9%, 20 ml) and the reaction mixture was stirred at 0.degree. C. for 1 h. After evaporation the residue was dissolved in water and extracted with ethyl acetate. The dried organic phases were evaporated and the residue purified by column chromatography (SiO.sub.2, eluent: ethyl acetate/methanol (4:1)). The title compound was crystallized as the oxalate salt from acetone to yield 280 mg. (M.p. 158.degree. C.; M.sup.+ : 253; Compound 4).

EXAMPLE 5

A. 3-(3-lsopropoxy-1,2,5-thiadiazol-4-yl)pyridine

To a solution of sodium (290 mg, 12.5 mmol) in isopropanol (10 ml) was added 3-(3-chloro-1,2,5-thiadiazol-4-yl)pyridine (490 mg, 2.5 mmol). The mixture was stirred at 25.degree. C. for 18 h and evaporated. The residue was dissolved in water and extracted with ethyl acetate. The combined organic phases were dried and evaporated to yield 540 mg (98%) of the title compound.

B. 3-(3-lsopropoxy-1,2,5-thiadiazol-4-yl)-1-methylpyridinium iodide

A mixture of methyl iodide (0.3 ml, 5 mmol) and 3-(3-isopropoxy-1,2,5-thiadiazol-4-yl)pyridine (540 mg, 2.4 mmol) in acetone (5 ml) was stirred at room temperature for 18 h. The title compound precipitated from the solution and was collected by filtration to yield 0.68 g (77%).

C. 1,2,5,6-Tetrahydro-3-(3-isopropoxy-1,2,5-thiadiazol-4-yl)-1 -methylpyridine oxalate

Sodium borohydride (280 mg, 7.2 mmol) was added to a solution of 3-(3-isopropoxy-1,2,5-thiadiazol-4-yl)-1-methylpyridinium iodide (650 mg, 1.8 mmol) in ethanol (99.9%, 20 ml) and the reaction mixture was stirred at 0.degree. C. for 1 h. After evaporation the residue was dissolved in water and extracted with ethyl acetate. The dried organic phases were evaporated and the residue purified by column chromatography (SiO.sub.2, eluent: ethyl acetate/methanol (4:1)). The title compound was crystallized as the oxalate salt from acetone to yield 280 mg. (M.p. 164.degree. C.; M.sup.+ : 239; Compound 5).

EXAMPLE 6

A. 3-(3-Pentyloxy-1,2,5-thiadiazol-4-yl)pyridine

To a solution of sodium (230 mg, 10 mmol) in 1-pentanol (20 ml) was added 3-(3-chloro-1,2,5-thiadiazol-4-yl)pyridine (490 mg, 2.5 mmol). The mixture was stirred at 50.degree. C. for 3 h and evaporated. The residue was dissolved in water and extracted with methylene chloride. The combined organic phases were dried and evaporated to give the wanted compound.

B. 3-(3-Pentyloxy-1,2,5-thiadiazol-4-yl)-1-methylpyridinium iodide

A mixture of methyl iodide (0.3 ml, 5 mmol) and 3-(3-pentyloxy-1,2,5-thiadiazol-4-yl)pyridine (620 mg, 2.5 mmol) in acetone (5 ml) was stirred at room temperature for 18 h. The title compound precipitated from the solution and was collected by filtration to yield 0.81 g (84%).

C. 1,2,5,6-Tetrahydro-1-methyl-3-(3-pentyloxy-1,2,5-thiadiazol-4-yl)pyridineoxalate

Sodium borohydride (300 mg, 8 mmol) was added to a solution of 3-(3-pentyloxy-3,2,5-thiadiazol-4-yl)-1-methylpyridinium iodide (0.81 g, 2 mmol) in ethanol (99.9%, 20 ml) and the reaction mixture was stirred at 0.degree. C. for 1 h. After evaporation the residue was dissolved in water and extracted with ether. The dried organic phases were evaporated and the residue purified by column chromatography (SiO.sub.2, eluent: ethyl acetate/methanol (4:1)). The title compound was crystallized as the oxalate salt from acetone, and recrystallized from methanol to yield 220 mg. (M.p. 150.degree. C.; M.sup.+ : 267; Compound 6).

EXAMPLE 7

A. 3-(3-lsobutoxy-1,2,5-thiadiazol-4-yl)pyridine

To a solution of sodium (230 mg, 10 mmol) in isobutanol (10 ml) was added 3-(3-chloro-1,2,5-thiadiazol-4-yl)pyridine (490 mg, 2.5 mmol). The mixture was stirred at 50.degree. C. for 3 h and evaporated. The residue was dissolved in water and extracted with methylene chloride. The combined organic phases were dried and evaporated to give the wanted compound.

B. 3-(3-lsobutoxy-1,2,5-thiadiazol-4-yl)-1-methylpyridinium iodide

A mixture of methyl iodide (0.6 ml, 10 mmol) and 3-(3-isobutoxy-1,2,5-thiadiazol-4-yl)pyridine (588 mg, 2.5 mmol) in acetone (5 ml) was stirred at room temperature for 18 h. The title compound precipitated from the solution and was collected by filtration to yield 0.88 g (87%).

C. 1,2,5,6-Tetrahydro-3-(3-isobutoxy-1,2,5-thiadiazol-4-yl)-1-methylpyridineoxalate

Sodium borohydride (160 mg, 4.3 mmol) was added to a solution of 3-(3-isobutoxy-1,2,5-thiadiazol-4-yl)-1-methylpyridinium iodide (0.82 g, 2.2 mmol) in ethanol (99.9%, 20 ml) and the reaction mixture was stirred at 0.degree. C. for 1 h. After evaporation the residue was dissolved in water and extracted with ethyl acetate. The dried organic phases were evaporated and the residue purified by column chromatography (SiO.sub.2, eluent: ethyl acetate/methanol (4:1)). The title compound was crystallized as the oxalate salt from acetone to yield 400 mg. (M.p. 135.degree. C.; M.sup.+ : 253; Compound 7).

EXAMPLE 8

A. 3-(3-lsopentyloxy-1,2,5-thiadiazol-4-yl)pyridine

To a solution of sodium (230 mg, 10 mmol) in isopentanol (20 ml) was added 3-(3-chloro-1,2,5-thiadiazol-4-yl)pyridine (490 mg, 2.5 mmol). The mixture was stirred at 50.degree. C. for 2 h and evaporated. The residue was dissolved in water and extracted with ether. The combined organic phases were dried and evaporated to give the wanted compound.

B. 3-(3-lsopentyloxy-1,2,5-thiadiazol-4-yl)-1-methylpyridinium iodide

A mixture of methyl iodide (0.5 ml, 10 mmol) and 3-(3-isopentyloxy-1,2,5-thiadiazol-4-yl)pyridine (622 mg, 2.5 mmol) in acetone (5 ml) was stirred at room temperature for 18 h. The title compound precipitated from the solution and was collected by filtration to yield 0.78 g (81%).

C. 1,2,5,6-Tetrahydro-3-(3-isopentyloxy-1,2,5-thiadiazol-4-yl)-1-methylpyridine oxalate

Sodium borohydride (150 mg, 4 mmol) was added to a solution of 3-(3-isopentyloxy-1,2,5-thiadiazol-4-yl)-1-methylpyridinium iodide (780 mg, 2 mmol) in ethanol (99.9%, 20 ml) and the reaction mixture was stirred at 0.degree. C. for 1 h. After evaporation the residue was dissolved in water and extracted with ethyl acetate. The dried organic phases were evaporated and the residue purified by column chromatography (SiO.sub.2, eluent: ethyl acetate/methanol (4:1)). The title compound was crystallized as the oxalate salt from acetone to yield 350 mg. (M.p. 152.degree. C.; M.sup.+ : 267; Compound 8).

EXAMPLE 9

A. 3-(3-Hexyloxy-1,2,5-thiadiazol-4-yl)pyridine

To a solution of sodium (230 mg, 10 mmol) in 1-hexanol (15 ml) was added 3-(3-chloro-1,2,5-thiadiazol-4-yl)pyridine (490 mg, 2.5 mmol). The mixture was stirred at 50.degree. C. for 2 h and evaporated. The residue was dissolved in water and extracted with ether. The combined organic phases were dried and evaporated to give the wanted compound.

B. 3-(3-Hexyloxy-1,2,5-thiadiazol-4-yl)-1-methylpyridinium iodide

A mixture of methyl iodide (0.5 ml, 7.5 mmol) and 3-(3-hexyloxy-1,2,5-thiadiazol-4-yl)pyridine (658 mg, 2.5 mmol) in acetone (5 ml) was stirred at room temperature for 18 h. The title compound precipitated from the solution and was collected by filtration to yield 0.81 g (80%).

C. 3-(3-Hexyloxy-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetetrahydro-1-methylpyridine oxalate

Sodium borohydride (230 mg, 6 mmol) was added to a solution of 3-(3-hexyloxy-1,2,5-thiadiazol-4-yl)-1-methylpyridinium iodide (810 mg, 2 mmol) in ethanol (99.9%, 20 ml) and the reaction mixture was stirred at room temperature for 1 h. After evaporation the residue was dissolved in water and extracted with ethyl acetate. The dried organic phases were evaporated and the residue purified by column chromatography (SiO.sub.2, eluent: ethyl acetate/methanol (4:1)). The title compound was crystallized as the oxalate salt from acetone to yield 350 mg. (M.p. 148.degree. C.; M.sup.+ : 281; Compound 9).

EXAMPLE 10

A. 3-(3-Benzyloxy-1,2,5-thiadiazol-4-yl)pyridine

To a solution of sodium (490 mg, 2.5 mmol) in benzyl alcohol (15 ml) was added 3-(3-chloro-1,2,5-thiadiazol-4-yl)pyridine (490 mg, 2.5 mmol). The mixture was stirred at 50.degree. C. for 2 h and evaporated. The residue was dissolved in water and extracted with ether. The combined organic phases were dried and evaporated to give the wanted compound.

B. 3-(3-Benzyloxy-1,2,5-thiadiazol-4-yl)-1-methylpyridinium iodide

A mixture of methyl iodide (0.5 ml, 7.5 mmol) and 3-(3-benzyloxy-1,2,5-thiadiazol-4-yl)pyridine (673 mg, 2.5 mmol) in acetone (5 ml) was stirred at room temperature for 18 h. The title compound precipitated from the solution and was collected by filtration to yield 0.75 9 (73%).

C. 3-(3-Benzyloxy-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridineoxalate

Sodium borohydride (230 mg, 6 mmol) was added to a solution of 3-(3-benzyloxy-1,2,5-thiadiazol-4-yl)-1-methylpyridinium iodide (750 mg, 1.8 mmol) in ethanol (99.9%, 20 ml) and the reaction mixture was stirred at 0.degree. C. for 1 h. After evaporation the residue was dissolved in water and extracted with ethyl acetate. The dried organic phases were evaporated and the residue purified by column chromatography (SiO.sub.2, eluent: ethyl acetate/methanol (4:1)). The title compound was crystallized as the oxalate salt from acetone to yield 340 mg. (M.p. 149.degree. C.; M.sup.+ : 287; Compound 10).

EXAMPLE 11

A. 3-(3-(3-Butenyloxy)-1,2,5-thiadiazol-4-yl)pyridine

To a solution of 3-buten-1-ol (540 mg, 7.5 mmol) and sodium hydride (180 mg, 7.5 mmol) in dry tetrahydrofuran was added a solution of 3-(3-chloro-1,2,5-thiadiazol-4-yl)pyridine (490 mg, 2.5 mmol) in dry tetrahydrofuran. The reaction mixture was stirred at room temperature for 1 h. Water was added and the mixture was extracted with ether. The ether phase was dried and evaporated to yield 650 mg of the title compound.

B. 3-(3-(3-Butenyloxy)-1,2,5-thiadiazol-4-yl)-1-methylpyridinium iodide

A mixture of methyl iodide (0.5 ml, 7.5 mmol) and 3-(3-(3-butenyloxy)-1,2,5-thiadiazol-4-yl)pyridine (583 mg, 2.5 mmol) in acetone (5 ml) was stirred at room temperature for 18 h. The title compound precipitated from the solution and was collected by filtration to yield 890 mg (96%).

C. 3-(3-(3-Butenyloxy)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate

Sodium borohydride (210 mg, 5.5 mmol) was added to a solution of 3-(3-(3-butenyloxy-1,2,5-thiadiazol-4-yl)-1-methylpyridinium iodide (1.03 g, 2.8 mmol) in ethanol (99.9%, 20 ml) and the reaction mixture was stirred at 0.degree. C. for 1 h. After evaporation the residue was dissolved in water and extracted with ethyl acetate. The dried organic phases were evaporated and the residue purified by column chromatography (SiO.sub.2, eluent: ethyl acetate/methanol (4:1)). The title compound was crystallized as the oxalate salt from acetone to yield 380 mg. (M.p. 141.degree. C.; M.sup.+ : 251; Compound 11).

EXAMPLE 12

A. 3-(3-(2-Butynyloxy)-1,2,5-thiadiazol-4-yl)pyridine

To a solution of 2-butyn-1-ol (530 mg, 7.5 mmol) and sodiumhydride (180 mg, 7.5 mmol) in dry tetrahydrofuran was added a solution of 3-(3-chloro-1,2,5-thiadiazol-4-yl)pyridine (490 mg, 2.5 mmol) in dry tetrahydrofuran. The reaction mixture was stirred at room temperature for 2 h. Water was added and the mixture was extracted with ether. The ether phase was dried and evaporated to give the title compound.

B. 3-(3-(2-Butynyloxy)-1,2,5-thiadiazol-4-yl)-1 -methylpyridinium iodide

A mixture of methyl iodide (0.5 ml, 7.5 mmol) and 3-(3-(2-butynyloxy)-1,2,5-thiadiazol-4-yl)pyridine (578 mg, 2.5 mmol) in acetone (5 ml) was stirred at room temperature for 18 h. The title compound precipitated from the solution and was collected by filtration to yield 0.88 g (95%).

C. 3-(3-(2-Butynyloxy)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate

Sodium borohydride (180 mg, 4.7 mmol) was added to a solution of 3-(3-(2-butynyloxy)-1,2,5-thiadiazol-4-yl)-1-methylpyridinium iodide (0.88 g, 2.35 mmol) in ethanol (99.9%, 20 ml) and the reaction mixture was stirred at 0.degree. C. for 1 h. After evaporation the residue was dissolved in water and extracted with ethyl acetate. The dried organic phases were evaporated and the residue purified by column chromatography (SiO.sub.2, eluent: ethyl acetate/methanol (4:1)). The title compound was crystallized as the oxalate salt from acetone, and recrystallized in methanol to yield 140 mg. (M.p. 158.degree. C.; M.sup.+ : 249; Compound 12).

EXAMPLE 13

A. 3-(3-Propargyloxy-1,2,5-thiadiazol-4-yl)pyridine

To a solution of propargyl alcohol (420 mg, 7.5 mmol) and sodium hydride (180 mg, 7.5 mmol) in dry tetrahydrofuran was added a solution of 3-(3-chloro-1,2,5-thiadiazol-4-yl)pyridine (490 mg, 2.5 mmol) in dry tetrahydrofuran. The reaction mixture was stirred at room temperature for 2 h. Water was added and the mixture was extracted with ether. The ether phase was dried and evaporated to yield 530 mg (98%) of the title compound.

B. 3-(3-Propargyloxy-1,2,5-thiadiazol-4-yl)-1-methylpyridinium iodide

A mixture of methyl iodide (0.45 ml, 7.2 mmol) and 3-(3-propargyloxy-1,2,5-thiadiazol-4-yl)pyridine (430 mg, 2.4 mmol) in acetone (5 ml) was stirred at room temperature for 18 h. The title compound precipitated from the solution and was collected by filtration to yield 0.58 g (67%).

C. 1,2,5,6-Tetrahydro-1-methyl-3-(3-propargyloxy-1,2,5-thiadiazol-4-yl)pyridine oxalate

Sodium borohydride (230 mg, 6 mmol) was added to a solution of 3-(3-propargyloxy-1,2,5-thiadiazol-4-yl)-1-methylpyridinium iodide (0.68 g, 1.9 mmol) in ethanol (99.9%, 20 ml) and the reaction mixture was stirred at 0.degree. C. for 1 h. After evaporation the residue was dissolved in water and extracted with ethyl acetate. The dried organic phases were evaporated and the residue purified by column chromatography (SiO.sub.2, eluent: ethyl acetate/methanol (4:1)). The title compound was crystallized as the oxalate salt from acetone to yield 200 mg. (M.p. 155.degree. C.; M.sup.+ : 235; Compound 13).

EXAMPLE 14

A. 3-(3-Cyclopropylmethoxy-1,2,5-thiadiazol-4-yl)pyridine

To a solution of cyclopropylcarbinol (360 mg, 5 mmol) and sodium hydride (110 mg, 5 mmol) in dry tetrahydrofuran was added a solution of 3-(3-chloro-1,2,5-thiadiazol-4-yl)pyridine (490 mg, 2.5 mmol) in dry tetrahydrofuran. The reaction mixture was stirred at room temperature for 3 h. Water was added and the mixture was extracted with ether. The ether phase was dried and evaporated to yield 400 mg (69%) of the title compound.

B. 3-(3-Cyclopropylmethoxy-1,2,5-thiadiazol-4-yl)-1-methylpyridinium iodide

A mixture of methyl iodide (0.25 ml, 4 mmol) and 3-(3-cyclopropylmethoxy-1,2,5-thiadiazol-4yl)pyridine (400 mg, 1.7 mmol) in acetone (5 ml) was stirred at room temperature for 36 h. The title compound precipitated from the solution and was collected by filtration to yield 0.41 g (65%).

C. 3-(3-Cyclopropylmethoxy-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate

Sodium borohydride (170 mg, 4.4 mmol) was added to a solution of 3-(3-cyclopropylmethoxy-1,2,5-thiadiazol-4-yl)-1-methylpyridinium iodide (410 mg, 1.1 mmol) in ethanol (99.9%, 20 ml) and the reaction mixture was stirred at 0.degree. C. for 1 h. After evaporation the residue was dissolved in water and extracted with ethyl acetate. The dried organic phases were evaporated and the residue purified by column chromatography (SiO.sub.2, eluent: ethyl acetate/methanol (4:1)). The title compound was crystallized as the oxalate salt from acetone to yield 130 mg. (M.p. 153.degree. C.; M.sup.+ : 251; Compound 14).

EXAMPLE 15

A. 3-(3-Chloro-1,2,5-thiadiazol-4-yl)-1-methylpyridinium iodide

A solution of 3-(3-chloro-1,2,5-thiadiazol-4-yl)pyridine (1.98 g, 10 mmol) and methyl iodide (4.25 g, 30 mmol) in acetone (10 ml) was stirred at room temperature for 16 h. The precipitate was collected by filtration to yield 3.40 g (100%) of the title compound.

B. 3-(3-Chloro-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate

To a suspension of sodium borohydride (330 mg, 8.6 mmol) in ethanol (20 ml) was added 3-(3-chloro-1,2,5-thiadiazol-4-yl)-1-methylpyridinium iodide (1.46 g, 4.3 mmol) at 0.degree. C. The reaction mixture was stirred for 1 h at 0.degree. C. Water was added and the mixture was extracted with ethyl acetate. After drying, the ethyl acetate phase was evaporated and the residue purified by column chromatography (eluent: ethyl acetate: methanol (4:1)). Yield: 880 mg (95%). Crystallization with oxalic acid from acetone gave the title compound. (M.p. 124.degree. C.; M.sup.+ : 215 and 217; Compound 16).

C. 1,2,5,6Tetrahydro-3-(3-methoxyethoxy-1,2,5-thiadiazol-4-yl)-1-methylpyridine oxalate

To a solution of sodium (120 mg, 5 mmol) in 2-methoxyethanol (10 ml) was added 3-(3-chloro-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate (310 mg, 1 mmol). The mixture was stirred at 50.degree. C. for 18 h and evaporated. The residue was dissolved in water and extracted with ethyl acetate. The combined organic phases were dried and evaporated. The title compound was crystallized as the oxalate salt from acetone to yield 270 mg. (M.p. 152.degree. C.; M.sup.+ : 253; Compound 15).

D. 3-(3-Chloro-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydropyridine hydrochloride

To a solution of 3-(3-chloro-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methyl-pyridine (670 mg, 3.1 mmol) in 1,2-dichloroethane (20 ml) was added a solution of 1-chloroethyl-chloroformate (440 mg, 3.1 mmol) in 1,2-dichloroethane at 0.degree. C. The reaction mixture was heated to 40.degree. C. for 2 h and evaporated. The residue was dissolved in methanol and heated to reflux for 1 h. After cooling to room temperature the precipitate was collected by filtration to yield 320 mg (41%). (M.p. 224.degree. C.; M.sup.+ : 201 and 203; Compound 17).

E. 3-(3-Butoxy-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydropyridine oxalate

To a solution of sodium (150 mg, 6.5 mmol) in 1-butanol (15 ml) was added 3-(3-chloro-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydropyridine hydrochloride (240 mg, 1 mmol). The reaction mixture was stirred at 50.degree. C. for 1 h. After evaporation the residue was dissolved in water and extracted with ethyl acetate. The ethyl acetate phase was dried and evaporated to give an oil (200 mg). Crystallization as the oxalate salt from acetone gave the title compound. Yield: 170 mg (52%). (M.p. 173.degree.-174.degree. C.; M.sup.+ : 239; Compound 18).

EXAMPLE 16

A. 3-(3-Chloro-1,2,5-thiadiazol-4-yl)-1-ethylpyridiniumiodide

A solution of 3-(3-chloro-1,2,5thiadiazol-4-yl)pyridine (1.13 g, 5.7 mmol) and ethyl iodide (22.65 g, 17 mmol) in acetone (15 ml) was stirred at 40.degree. C. for 16 h. The precipitate was collected by filtration giving the title compound. Yield: 510 mg (26%).

B. 3-(3-Chloro-1,2,5-thiadiazol-4-yl)-1-ethyl-1,2,5,6-tetrahydropyridine oxalate

To a suspension of sodium borohydride (170 mg, 4.5 mmol) in ethanol (10 ml) was added 3-(3-chloro-1,2,5-thiadiazol-4-yl)-1-ethylpyridinium iodide (510 mg, 1.5 mmol) at 0.degree. C. The mixture was stirred for 1 h at 0.degree. C. Water was added and the mixture was extracted with ethyl acetate. After drying, the ethyl acetate phase was evaporated and the residue purified by column chromatography (eluent: ethyl acetate/methanol (4:1)). Crystallization with oxalic acid from acetone gave the title compound to yield 70 mg. (M.p. 143.degree. C.; M.sup.+ : 229 and 231; Compound 19).

EXAMPLE 17

A. 3-(3Ethoxy-1,2,5-thiadiazol-4-yl)-1-ethylpyridinium iodide

A solution of 3-(3-ethoxy-1,2,5-thiadiazol-4-yl)pyridine (0.90 g, 4.3 mmol) and ethyl iodide (2.03 g, 13 mmol) in acetone (4 ml) was stirred at 40.degree. C. for 16 h. The precipitate was collected by filtration giving the title compound to yield 1.34 g (86%).

B. 3-(3-Ethoxy-1,2,5-thiadiazol-4-yl)-1-ethyl-1,2,5,6-tetrahydropyridine oxalate

To a suspension of sodium borohydride (410 mg, 10.8 mmol) in ethanol (10 ml) was added 3-(3-ethoxy-1,2,5-thiadiazol-4-yl)-1-ethylpyridinium iodide (1.32 g, 3.6 mmol) at 0.degree. C. The mixture was stirred for 1 h at 0.degree. C. Water was added and the mixture was extracted with ethyl acetate. After drying, the ethyl acetate phase was evaporated and the residue purified by column chromatography (eluent: ethyl acetate/methanol (4:1)). Crystallization with oxalic acid from acetone gave a yield of 0.49 g of the title compound. (M.p. 120.degree.-122.degree. C.; M+: 239; Compound 20).

The following compounds were prepared in exactly the same manner:

3-(3-Hexylthio-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-ethylpyridine oxalate from 3-(3-Hexylthio-1,2,5-thiadiazol-4-yl)pyridine. M.p. 134.degree.-135.degree. C. Compound 209.

3-(3-Ethylthio-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-ethylpyridine oxalate from 3-(3-ethylthio-1,2,5-thiadiazol-4-yl)pyridine. M.p. 151.degree.-152.degree. C. Compound 210.

3-(3-Hexyloxy-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-ethylpyridine oxalate from 3-(3-hexyloxy-1,2,5-thiadiazol-4-yl)pyridine. M.p. 138.degree.-39.degree. C. Compound 211.

EXAMPLE 18

3-(3-Heptyloxy-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate

To a solution of sodium (120 mg, 5 mmol) in 1-heptanol (10 ml) was added 3-(3-chloro-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate (310 mg, 1 mmol). The reaction mixture was stirred at 50.degree. C. for 18 h. After evaporation the residue was dissolved in water and extracted with ethyl acetate. The ethyl acetate phase was dried and evaporated to give an oil. Crystallization as the oxalate salt from acetone gave the title compound. Yield: 270 mg (70%). (M.p. 152.degree. C.; M.sup.+ : 295; Compound 21).

EXAMPLE 19

A. 3-(3-(3-Pentynyloxy)-1,2,5-thiadiazol-4-yl)pyridine

To a solution of 3-pentyn-1-ol (750 mg, 9 mmol) and sodium hydride (310 mg, 9 mmol) in dry tetrahydrofuran was added a solution of 3-(3-chloro-1,2,5-thiadiazol-4-yl)pyridine (590 mg, 3 mmol) in dry tetrahydrofuran. The reaction mixture was stirred at room temperature for 1 h. Water was added and the mixture was extracted with ether. The ether phase was dried and evaporated to give the title compound.

B. 3-(3-(3-Pentynyloxy)-1,2,5-thiadiazol-4-yl)-1-methylpyridinium iodide

A mixture of methyl iodide (0.6 ml, 9 mmol) and 3-(3-(3-pentynyloxy)-1,2,5-thiadiazol-4-yl)pyridine (3 mmol) in acetone (10 ml) was stirred at room temperature for 18 h. The title compound precipitated from the solution and was collected by filtration to yield 0.68 g (59%).

C. 3-(3-(3-Pentynyloxy)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate

Sodium borohydride (150 mg, 4 mmol) was added to a solution of 3-(3-(3-pentynyloxy)-1,2,5-thiadiazol-4-yl)-1-methylpyridinium iodide (0.68 g, 1.7 mmol) in ethanol (99.9%, 15 ml) and the reaction mixture was stirred at -10.degree. C. for 1 h. After evaporation the residue was dissolved in water and extracted with ethyl acetate. The dried organic phases were evaporated and the residue purified by column chromatography (SiO.sub.2, eluent: ethyl acetate/methanol (4:1)). The title compound was crystallized as the oxalate salt from acetone to yield 240 mg. (M.p. 166.degree.-167.degree. C.; M.sup.+ : 263; Compound 22).

EXAMPLE 20

A. 3-(3-(4-Pentenyloxy)-1,2,5-thiadiazol-4-yl)pyridine

To a solution of 4-penten-1-ol (640 mg, 7.5 mmol) and sodium hydride (260 mg, 7.5 mmol) in dry tetrahydrofuran was added a solution of 3-(3-chloro-1,2,5-thiadiazol-4-yl)pyridine (490 mg, 2.5 mmol) in dry tetrahydrofuran. The reaction mixture was stirred at room temperature for 1 h. Water was added and the mixture was extracted with ether. The ether phase was dried and evaporated to give the title compound.

B. 3-(3-(4-Pentenyloxy)-1,2,5-thiadiazol-4-yl)-1-methylpyridinium iodide

A mixture of methyl iodide (0.5 ml, 7.5 mmol) and 3-(3-(4-pentenyloxy)-1,2,5-thiadiazol-4-yl)pyridine (2.5 mmol) in acetone (10 ml) was stirred at room temperature for 18 h. The title compound precipitated from the solution and was collected by filtration to yield 0.67 g (69%).

C. 3-(3-(4-Pentenyloxy)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate

Sodium borohydride (150 mg, 4 mmol) was added to a solution of 3-(3-(4-pentenyloxy)-1,2,5-thiadiazol-4-yl)-1-methylpyridinium iodide (0.67 g, 1.7 mmol) in ethanol (99.9%, 15 ml) and the reaction mixture was stirred at -10.degree. C. for 1 h. After evaporation the residue was dissolved in water and extracted with ethyl acetate. The dried organic phases were evaporated and the residue purified by column chromatography (SiO.sub.2, eluent: ethyl acetate/methanol (4:1)). The title compound was crystallized as the oxalate salt from acetone to yield 150 mg. (M.p. 141.degree.-142.degree. C., M.sup.+ : 265; Compound 23).

EXAMPLE 21

A. 3-(3-(2-Propenyloxy)-1,2,5-thiadiazol-4-yl)pyridine

To a solution of allyl alcohol (650 mg, 9 mmol) and sodium hydride (310 mg, 9 mmol) in dry tetrahydrofuran was added a solution of 3-(3-chloro-1,2,5-thiadiazol-4-yl)pyridine (590 mg, 3 mmol) in dry tetrahydrofuran. The reaction mixture was stirred at room temperature for 1 h. Water was added and the mixture was extracted with ether. The ether phase was dried and evaporated to give the title compound.

B. 3-(3-(2-Propenyloxy)-1,2,5-thiadiazol-4-yl)-1-methylpyridinium iodide

A mixture of methyl iodide (0.4 ml, 6 mmol) and 3-(3-(2-propenyloxy)-1,2,5-thiadiazol-4-yl)pyridine (3 mmol) in acetone (5 ml) was stirred at room temperature for 18 h. The title compound precipitiated from the solution and was collected by filtration to give 0.96 9 (88%).

C. 3-(3-(2-Propenyloxy)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate

Sodium borohydride (210 mg, 5.5 mmol) was added to a solution of 3-(3-(2-propenyloxy)-1,2,5-thiadiazol-4-yl)-1-methylpyridinium iodide (0.96 g, 2.6 mmol) in ethanol (99.9%, 25 ml) and the reaction mixture was stirred at -10.degree. C. for 1 h. After evaporation the residue was dissolved in water and extracted with ethyl acetate. The dried organic phases were evaporated and the residue purified by column chromatography (SiO.sub.2, eluent: ethyl acetate/methanol (4:1)). The title compound was crystallized as the oxalate salt from acetone to yield 270 mg. (M.p. 136.degree.-137.degree. C.; M.sup.+ : 237; Compound 24).

EXAMPLE 22

A. 3-(3-Octyloxy-1,2,5-thiadiazol-4-yl)pyridine

To a solution of sodium (350 mg, 15 mmol) in 1-octanol (10 ml) was added 3-(3-chloro-1,2,5-thiadiazol-4-yl)pyridine (590 mg, 3 mmol). The mixture was stirred at 50.degree. C. for 1 h and evaporated. The residue was dissolved in water and extracted with methylene chloride. The combined organic phases were dried and evaporated to give the title compound.

B. 3-(3-Octyloxy-1,2,5-thiadiazol-4-yl)-1-methylpyridinium iodide

A mixture of methyl iodide (1 ml, 15 mmol) and 3-(3-octyloxy-1,2,5-thiadiazol-4-yl)pyridine (3 mmol) in acetone (5 ml) was stirred at room temperature for 18 h. The title compound precipitated from the solution and was collected by filtration to yield 0.81 9 (62%).

C. 3-(3-Octyloxy-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate

Sodium borohydride (210 mg, 5.6 mmol) was added to a solution of 3-(3-octyloxy-1,2,5-thiadiazol-4-yl)-1-methylpyrdinium iodide (0.81 g, 1.87 mmol) in ethanol (99.9%, 10 ml) and the reaction mixture was stirred at -10.degree. C. for 1 h. After evaporation the residue was dissolved in water and extracted with ethyl acetate. The dried organic phases were evaporated and the residue purified by column chromatography (SiO.sub.2, eluent: ethyl acetate/methanol (4:1)). The title compound was crystallized as the oxalate salt from acetone to yield 330 mg. (M.p. 144.degree.-145.degree. C.; M.sup.+ : 309; Compound 25).

EXAMPLE 23

A. 3-(3-(3-Hexynyloxy)-1,2,5-thiadiazol-4-yl)pyridine

To a solution of 3-hexyn-1-ol (880 mg, 9 mmol) and sodium hydride (310 mg, 9 mmol) in dry tetrahydrofuran was added a solution of 3-(3-chloro-1,2,5-thiadiazol-4-yl)pyridine (590 mg, 3 mmol) in dry tetrahydrofuran. The reaction mixture was stirred at room temperature for 1 h. Water was added and the mixture was extracted with ether. The ether phase was dried and evaporated to give the title compound.

B. 3-(3-(3-Hexynyloxy)-1,2,5-thiadiazol-4-yl)-1-methylpyridinium iodide

A mixture of methyl iodide (1 ml, 15 mmol) and 3-(3-(3-hexynyloxy)-1,2,5-thiadiazol-4-yl)pyridine (3 mmol) in acetone (5 ml) was stirred at room temperatue for 18 h. The title compound precipitated from the solution and was collected by filtration to yield 0.85 g (71%).

C. 3-(3-(3-Hexynyloxy)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate

Sodium borohydride (190 mg, 5 mmol) was added to a solution of 3-(3-(3-hexynyloxy)-1,2,5-thiadiazol-4-yl)-1-methylpyridinium iodide (0.85 g, 2.1 mmol) in ethanol (99.9%, 10 ml) and the reaction mixture was stirred at -10.degree. C. for 1 h. After evaporation the residue was dissolved in water and extracted with ethyl acetate. The dried organic phases were evaporated and the residue purified by column chromatography (SiO.sub.2, eluent: ethyl acetate/methanol (4:1)). The title compound was crystallized as the oxalate salt from acetone to yield 350 mg. (M.p. 174.degree.-175.degree. C.; M.sup.+ : 277; Compound 26).

EXAMPLE 24

A. 3-(3-(3-Methyl-2-butenyloxy)-1,2,5-thiadiazol-4-yl)pyridine

To a solution of 3-methyl-2-buten-1-ol (780 mg, 9 mmol) and sodiumhydride (310 mg, 9 mmol) in dry tetrahydrofuran was added a solution of 3-(3-chloro-1,2,5-thiadiazol-4-yl)pyridine (590 mg, 3 mmol) in dry tetrahydrofuran. The reaction mixture was stirred at room temperature for 0.3 h. Water was added and the mixture was extracted with ether. The ether phase was dried and evaporated to give the title compound.

B. 3-(3-(3-Methyl-2-butenyloxy)-1,2,5-thiadiazol-4-yl)-1-methylpyridinium iodide

A mixture of methyl iodide (1 ml, 15 mmol) and 3-(3-(3-methyl-2-butenyloxy)-1,2,5-thiadiazol-4-yl)pyridine (3 mmol) in acetone (3 ml) was stirred at room temperature for 18 h. The title compound precipitated from the solution and was collected by filtration to yield 0.92 g (79%).

C. 3-(3-(3-Methyl-2-butenyloxy)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate

Sodium borohydride (220 mg, 6 mmol) was added to a solution of 3-(3-(3-methyl-2-butenyloxy)-1,2,5-thiadiazol-4-yl)-1-methylpyridinium iodide (0.92 g, 2.3 mmol) in ethanol (99.9%, 15 ml) and the reaction mixture was stirred at -10.degree. C. for 0.5 h. After evaporation the residue was dissolved in water and extracted with ethyl acetate. The dried organic phases were evaporated and the residue purified by column chromatography (SiO.sub.2, eluent: ethyl acetate/methanol (4:1)). The title compound was crystallized as the oxalate salt from acetone to yield 380 mg. (M.p. 150.degree.-151.degree. C.; M.sup.+ : 265; Compound 27).

EXAMPLE 25

A. 3-(3-(3-Butenyl-2-oxy)-1,2,5-thiadiazol-4-yl)pyridine

To a solution of 3-buten-2-ol (650 mg, 9 mmol) and sodium hydride (310 mg, 9 mmol) in dry tetrahydrofuran was added a solution of 3-(3-chloro-1,2,5-thiadiazol-4-yl)pyridine (590 mg, 3 mmol) in dry tetrahydroturan. The reaction mixture was stirred at room temperature for 18 h. Water was added and the mixture was extracted with ether. The ether phase was dried and evaporated to give the title compound.

B. 3-(3-(3-Butenyl-2-oxy) -1,2,5-thiadiazol-4yl)-1-methylpyridinium iodide

A mixture of methyl iodide (1 ml, 15 mmol) and 3-(3-(3-butenyl-2-oxy)-1,2,5-thiadiazol-4-yl)pyridine (3 mmol) in acetone (3 ml) was stirred at room temperature for 18 h. The title compound precipitated from the solution and was collected by filtration to yield 0.73 g (65%).

C. 3-(3-(3-Butenyl-2-oxy)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate

Sodium borohydride (190 mg, 5 mmol) was added to a solution of 3-(3-(3-butenyl-2-oxy)-1,2,5-thiadiazol-4-yl)-1-methylpyridinium iodide (0.73 g, 1.9 mmol) in ethanol (99.9%, 15 ml) and the reaction mixture was stirred at -10.degree. C. for 0.5 h. After evaporation the residue was dissolved in water and extracted with ethyl acetate. The dried organic phases were evaporated and the residue purified by column chromatography (SiO.sub.2, eluent: ethyl acetate/methanol (4:1)). The title compound was crystallized as the oxalate salt from acetone to yield 270 mg. (M.p. 134.degree.-135.degree. C.; M.sup.+ : 251; Compound 28).

EXAMPLE 26

A. 3-(3-(4-Hexenyloxy)-1,2,5-thiadiazol-4-yl)pyridine

To a solution of 4-hexen-1-ol (900 mg, 9 mmol) and sodium hydride (310 mg, 9 mmol) in dry tetrahydrofuran was added a solution of 3-(3-chloro-1,2,5-thiadiazol-4-yl)pyridine (590 mg, 3 mmol) in dry tetrahydrofuran. The reaction mixture was stirred at room temperature for 1 h. Water was added and the mixture was extracted with ether. The ether phase was dried and evaporated to give the title compound.

B. 3-(3-(4-Hexenyloxy)-1,2,5-thiadiazol-4-yl)-1-methylpyridinium iodide

A mixture of methyl iodide (1 ml, 15 mmol) and 3-(3-(4-hexenyloxy)-1,2,5-thiadiazol-4-yl)pyridine (3 mmol) in acetone (5 ml) was stirred at room temperature for 18 h. The title compound precipitated from the solution and was collected by filtration to yield 0.54 g (45%).

C. 3-(3-(4-Hexenyloxy)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate

Sodium borohydride (150 mg, 4 mmol) was added to a solution of 3-(3-(4-hexenyloxy)-1,2,5thiadiazol-4-yl)-1-methylpyridinium iodide (0.54 g, 1.3 mmol) in ethanol (99.9%, 15 ml) and the reaction mixture was stirred at -10.degree. C. for 0.5 h. After evaporation the residue was dissolved in water and extracted with ethyl acetate. The dried organic phases were evaporated and the residue purified by column chromatography (SiO.sub.2, eluent: ethyl acetate/methanol (4:1)). The title compound was crystallized as the oxalate salt from acetone to yield 190 mg. (M.p. 151.degree.-152.degree. C.; M.sup.+ : 279; Compound 29).

EXAMPLE 27

A. trans-3-(3-(3-Hexenyloxy)-1,2,5-thiadiazol-4-yl)pyridine

To a solution of trans-3-hexen-1-ol (900 mg, 9 mmol) and sodium hydride (310 mg, 9 mmol) in dry tetrahydrofuran was added a solution of 3-(3-chloro-1,2,5-thiadiazol-4-yl) pyridine (590 mg, 3 mmol) in dry tetrahydrofuran. The reaction mixture was stirred at room temperature for 1 h. Water was added and the mixture was extracted with ether. The ether phase was dried and evaporated to give the title compound.

B. trans-3-(3-(3-Hexenyloxy)-1,2,5-thiadiazol-4-yl)-1-methylpyridinium iodide

A mixture of methyl iodide (1 ml, 15 mmol) and trans-3-(3-(3-hexenyloxy)-1,2,5-thiadiazol-4-yl)pyridine (3 mmol) in acetone (5 ml) was stirred at room temperature for 18 h. The title compound precipitated from the solution and was collected by filtration to yield 0.90 g (75%).

C. trans-3-(3-(3-Hexenyloxy)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate

Sodium borohydride (190 mg, 5 mmol) was added to a solution of trans-3-(3-(3-hexenyloxy)-1,2,5-thiadiazol-4-yl)-1-methylpyridinium iodide (0.90 g, 2.2 mmol) in ethanol (99.9%, 15 ml) and the reaction mixture was stirred at -10.degree. C. for 0.5 h. After evaporation the residue was dissolved in water and extracted with ethyl acetate. The dried organic phases were evaporated and the residue purified by column chromatography (SiO.sub.2, eluent: ethyl acetate/methanol (4:1)). The title compound was crystallized as the oxalate salt from acetone to yield 420 mg. (M.p. 163.degree.-164.degree. C.; M.sup.+ : 279; Compound 30).

EXAMPLE 28

A. cis-3-(3-(2-Pentenyloxy)-1,2,5-thiadiazol-4-yl)-pyridine

To a solution of cis-2-penten-1-ol (780 mg, 9 mmol) and sodium hydride (310 mg, 9 mmol) in dry tetrahydrofuran was added a solution of 3-(3-chloro-1,2,5-thiadiazol-4-yl)pyridine (590 mg, 3 mmol) in dry tetrahydrofuran. The reaction mixture was stirred at room temperature for 1 h. Water was added and the mixture was extracted with ether. The ether phase was dried and evaporated to give the title compound.

B. cis-3-(3-(2-Pentenyloxy)-1,2,5-thiadiazol-4-yl)-1-methylpyridinium iodide

A mixture of methyl iodide (1 ml, 15 mmol) and cis-3-(3-(2-pentenyloxy)-1,2,5-thiadiazol-4-yl)pyridine (3 mmol) in acetone (5 ml) was stirred at room temperature for 18 h. The title compound precipitated from the solution and was collected by filtration to yield 0.53 9 (46%).

C. cis-3-(3-(2-Pentenyloxy)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate

Sodium borohydride (150 mg, 4 mmol) was added to a solution of cis-3-(3-(2-pentenyloxy)-1,2,5-thiadiazol-4-yl)-1-methylpyridinium iodide (0.53 g, 1.3 mmol) in ethanol (99.9%, 15 ml) and the reaction mixture was stirred at -10.degree. C. for 0.5 h. After evaporation the residue was dissolved in water and extracted with ethyl acetate. The dried organic phases were evaporated and the residue purified by column chromatography (SiO.sub.2, eluent: ethyl acetate/methanol (4:1)). The title compound was crystallized as the oxalate salt from acetone to yield 210 mg. (M.p. 143.degree.-144.degree. C.; M.sup.+ : 265; Compound 31).

EXAMPLE 29

A. cis-3-(3-(2-Hexenyloxy)-1,2,5-thiadiazol-4-yl)pyridine

To a solution of cis-2-hexen-1-ol (900 mg, 9 mmol) and sodium hydride (310 mg, 9 mmol) in dry tetrahydrofuran was added a solution of 3-(3-chloro-1,2,5-thiadiazol-4-yl) pyridine (590 mg, 3 mmol) in dry tetrahydrofuran. The reaction mixture was stirred at room temperature for 1 h. Water was added and the mixture was extracted with ether. The ether phase was dried and evaporated to give the title compound.

B. cis-3-(3-(2-Hexenyloxy)-1,2,5-thiadiazol-4-yl)-1-methylpyridinium iodide

A mixture of methyl iodide (0.5 ml, 7.5 mmol) and cis-3-(3-(2-hexenyloxy)-1,2,5-thiadiazol-4-yl)pyridine (3 mmol) in acetone (4 ml) was stirred at room temperature for 18 h. The title compound precipitated from the solution and was collected by filtration.

C. cis-3-(3-(2-Hexenyloxy)-1,2,5-thiadiazol-4yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate

Sodium borohydride (150 mg, 4 mmol) was added to a solution of cis-3-(3-(2-hexenyloxy)-1,2,5-thiadiazol-4-yl)-1-methylpyridinium iodide (0.6 g, 1 mmol) in ethanol (99.9%, 20 ml) and the reaction mixture was stirred at -10.degree. C. for 0.5 h. After evaporation the residue was dissolved in water and extracted with ethyl acetate. The dried organic phases were evaporated and the residue purified by column chromatography (SiO.sub.2, eluent: ethyl acetate/methanol (4:1)). The title compound was crystallized as the oxalate salt from acetone to yield 150 mg. (M.p. 122.degree.-123.degree. C.; M+: 279; Compound 32).

EXAMPLE 30

A. 3-(3-(5-Hexenyloxy)-1,2,5-thiadiazol-4-yl)pyridine

To a solution of 5-hexen-1-ol (900 mg, 9 mmol) and sodium hydride (310 mg, 9 mmol) in dry tetrahydrofuran was added a solution of 3-(3-chloro-1,2,5-thiadiazol-4-yl)pyridine (590 mg, 3 mmol) in dry tetrahydrofuran. The reaction mixture was stirred at room temperature for 1 h. Water was added and the mixture was extracted with ether. The ether phase was dried and evaporated to give the title compound.

B. 3-(3-(5-Hexenyloxy)-1,2,5-thiadiazol-4-yl)-1-methylpyridinium iodide

A mixture of methyl iodide (0.5 ml, 7.5 mmol) and 3-(3-(5-hexenyloxy)-1,2,5-thiadiazol-4-yl)pyridine (3 mmol) in acetone (5 ml) was stirred at room temperature for 18 h. The title compound precipitated from the solution and was collected by filtration to yield 0.75 9 (62%).

C. 3-(3-(5-Hexenyloxy)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate

Sodium borohydride (150 mg, 4 mmol) was added to a solution of 3-(3-(5-hexenyloxy)-1,2,5-thiadiazol-4-yl)-1-methylpyridinium iodide (0.75 g, 1.8 mmol) in ethanol (99.9%, 20 ml) and the reaction mixture was stirred at -10.degree. C. for 0.5 h. After evaporation the residue was dissolved in water and extracted with ethyl acetate. The dried organic phases were evaporated and the residue purified by column chromatography (SiO.sub.2, eluent: ethyl acetate/methanol (4:1)). The title compound was crystallized as the oxalate salt from acetone to yield 250 mg. (M.p. 137.degree.-138.degree. C.; M.sup.+ : 279; Compound 33).

EXAMPLE 31

A. cis-3-(3-(3-Hexenyloxy)-1,2,5-thiadiazol-4-yl)pyridine

To a solution of cis-3-hexen-1-ol (900 mg, 9 mmol) and sodium hydride (310 mg, 9 mmol) in dry tetrahydrofuran was added a solution of 3-(3-chloro-1,2,5-thiadiazol-4-yl) pyridine (590 mg, 3 mmol) in dry tetrahydrofuran. The reaction mixture was stirred at room temperature for 1 h. Water was added and the mixture was extracted with ether. The ether phase was dried and evaporated to give the title compound.

B. cis-3-(3-(3-Hexenyloxy)-1,2,5-thiadiazol-4-yl)-1 -methylpyridinium iodide

A mixture of methyl iodide (0.5 ml, 7.5 mmol) and cis-3-(3-(3-hexenyloxy)-1,2,5-thiadiazol-4-yl)pyridine (3 mmol) in acetone (5 ml) was stirred at room temperature for 18 h. The title compound precipitated from the solution and was collected by filtration to yield 0.9 g (46%).

C. cis-3-(3-(3-Hexenyloxy)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate

Sodium borohydride (230 mg, 6 mmol) was added to a solution of cis-3-(3-(3-hexenyloxy)-1,2,5-thiadiazol-4-yl)-1-methylpyridinium iodide (0.90 g, 2.2 mmol) in ethanol (99.9%, 15 ml) and the reaction mixture was stirred at -10.degree. C. for 0.5 h. After evaporation the residue was dissolved in water and extracted with ethyl acetate. The dried organic phases were evaporated and the residue purified by column chromatography (SiO.sub.2, eluent: ethyl acetate/methanol (4:1)). The title compound was crystallized as the oxalate salt from acetone to yield 300 mg. (M.p. 149.degree.-150.degree. C.; M.sup.+ : 279; Compound 34).

EXAMPLE 32

A. trans-3-(3-(2-Hexenyloxy)-1,2,5-thiadiazol-4-yl)pyridine

To a solution of trans-2-hexen-1-ol (900 mg, 9 mmol) and sodium hydride (310 mg, 9 mmol) in dry tetrahydrofuran was added a solution of 3-(3-chloro-1,2,5-thiadiazol-4-yl) pyridine (590 mg, 3 mmol) in dry tetrahydrofuran. The reaction mixture was stirred at room temperature for 1 h. Water was added and the mixture was extracted with ether. The ether phase was dried and evaporated to give the title compound.

B. trans-3-(3-(2-Hexenyloxy)-1,2,5-thiadiazol-4-yl)-1-methylpyridinium iodide

A mixture of methyl iodide (0.5 ml, 7.5 mmol) and trans-3-(3-(2-hexenyloxy)-1,2,5-thiadiazol-4-yl)pyridine (3 mmol) in acetone (5 ml) was stirred at room temperature for 18 h. The title compound precipitated from the solution and was collected by filtration to yield 1.09 g (90%).

C. trans-3-(3-(2-Hexenyloxy)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate

Sodium borohydride (270 mg, 4 mmol) was added to a solution of trans-3-(3-(2-hexenyloxy)-1,2,5-thiadiazol-4-yl)-1-methylpyridinium iodide (1.09 g, 2.7 mmol) in ethanol (99.9%, 20 ml) and the reaction mixture was stirred at -10.degree. C. for 0.5 h. After evaporation the residue was dissolved in water and extracted with ethyl acetate. The dried organic phases were evaporated and the residue purified by column chromatography (SiO.sub.2, eluent: ethyl acetate/methanol (4:1)). The title compound was crystallized as the oxalate salt from acetone to yield 400 mg. (M.p. 130.degree.-131.degree. C.; M.sup.+ : 279; Compound 35).

EXAMPLE 33

A. 3-(1,2,5-Thiadiazol-3-yl)pyridine

To a solution of 1-butanethiol (2.7 g, 30 mmol) and sodium hydride (1.2 g, 30 mmol) in dry tetrahydrofuran was added a solution of 3-(3-chloro-1,2,5-thiadiazol-4-yl)pyridine (1.2 g, 6 mmol) in dry tetrahydrofuran. The reaction mixture was stirred at -10.degree. C. for 0.5 h. Water was added and the mixture was extracted with ether. The ether phase was dried and evaporated. The residue was purified by column chromatography (SiO.sub.2, eluent: ethyl acetate/methylene chloride (1:1)) to give the title compound.

B. 3-(1,2,5-Thiadiazol-3-yl)-1-methylpyridinium iodide

A mixture of methyl iodide (1 ml, 15 mmol) and 3-(1,2,5-thiadiazol-3-yl)pyridine (6 mmol) in acetone (5 ml) was stirred at room temperature for 18 h. The title compound precipitated from the solution and was collected by filtration to yield 1.2 g (74%).

C. 3-(1,2,5-Thiadiazol-3-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate

Sodium borohydride (380 mg, 10 mmol) was added to a solution of 3-(1,2,5-thiadiazol-3-yl)-1-methylpyridinium iodide (1.2 g, 4.4 mmol) in ethanol (99.9%, 20 ml) and the reaction mixture was stirred at -10.degree. C. for 0.5 h. After evaporation the residue was dissolved in water and extracted with ethyl acetate. The dried organic phases were evaporated and the residue purified by column chromatography (SiO.sub.2, eluent: ethyl acetate/ methanol (4:1)). The title compound was crystallized as the oxalate salt from acetone to yield 430 mg. (M.p. 189.degree.-190.degree. C.; M.sup.+ : 181; Compound 36).

EXAMPLE 34

1,2,5,6-Tetrahydro-3-(3-hexyloxy-1,2,5-thiadiazol-4-yl)pyridine oxalate

To a solution of 3-(3-hexyloxy-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine (0.70 g, 2.4 mmol) in 1,2-dichloroethane (20 ml) was added a solution of 1-chloroethyl-chloroformate (0.35 g, 2.4 mmol) in 1,2-dichloroethane at 0.degree. C. The reaction mixture was heated to 40.degree. C. for 2 h and evaporated. The residue was dissolved in methanol and heated to reflux for 1 h and evaporated. The residue was dissolved in diluted sodium hydroxide and extracted with ether. The combined ether phases were dried and evaporated. Crystallization as the oxalate salt from acetone gave the title compound in 72% (620 mg) yield. (M.p. 157.degree.-159.degree. C.; M.sup.+ : 267; Compound 37).

In exactly the same manner the following compounds were prepared:

3-(3-Ethoxy-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydropyridine hydrochloride. M.p. 217.degree.-218.degree. C. Compound 215.

3-(3-Ethylthio-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydropyridine hydrochloride. M.p. 181.degree.-182.degree. C. Compound 216.

3-(3-Propylthio-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydropyridine oxalate. M.p. 190.degree.-191.degree. C. Compound 217.

3-(3-Butylthio-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydropyridine oxalate. M.p. 182.degree.-183.degree. C. Compound 218.

3-(3-Pentylthio-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydropyridine oxalate. M.p. 181.degree.-182.degree. C. Compound 219.

3-(3-Hexylthio-1,2,5-thiadiazol-4-yl-1,2,5,6-tetrahydropyridine oxalate. M.p. 173.degree.-175.degree. C. Compound 220.

3-(3-(4-Pentynylthio)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydropyridine oxalate. M.p. 140.degree.-142.degree. C. Compound 221.

3-(3-(2,2,2-Trifluoroethylthio)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydropyridine hydrochloride. M.p. 105.degree.-110.degree. C. Compound 222.

3-(3-(2,2,2-Trifluoroethoxy)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydropyridine hydrochloride. M.p. 149.degree.-151.degree. C. Compound 223.

3-(3-(2-Phenoxyethylthio)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydropyridine oxalate. M.p. 191.degree.-192.degree. C. Compound 224.

EXAMPLE 35

A. 3-(3-(2-(2-Methoxyethoxy)ethoxy)-1,2,5-thiadiazol-4-yl)pyridine

To a solution of sodium (210 mg, 9 mmol) in 2-(2-methoxyethoxy)ethanol (10 ml) was added 3-(3-chloro-1,2,5-thiadiazol-4-yl)pyridine (590 mg, 3 mmol). The mixture was stirred at 50.degree. C. for 4 h and evaporated. The residue was dissolved in water and extracted with ether. The combined organic phases were dried and evaporated to give the title compound.

B. 3-(3-(2-(2-Methoxyethoxy)ethoxy)-1,2,5-thiadiazol-4-yl)-1-methylpyridinium iodide

A mixture of methyl iodide (0.5 nil, 9 mmol) and 3-(3-(2-(2-methoxyethoxy)-ethoxy)-1,2,5-thiadiazol-4-yl)pyridine (3 mmol) in acetone (10 ml) was stirred at room temperature for 18 h. The title compound precipitated from the solution and was collected by filtration to yield 0.76 g (60%).

C. 3-(3-(2-(2-Methoxyethoxy)ethoxy)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate

Sodium borohydride (150 mg, 4 mmol) was added to a solution of 3-(3-(2-(2-methoxyethoxy)ethoxy)-1,2,5-thiadiazol-4-yl)-1-methylpyridinium iodide (0.76 g, 1.8 mmol) in ethanol (99.9%, 20 ml) and the reaction mixture was stirred at -10.degree. C. for 1 h. After evaporation the residue was dissolved in water and extracted with ethyl acetate. The dried organic phases were evaporated and the residue purified by column chromatography (SiO.sub.2, eluent: ethyl acetate/methanol (4:1)). The title compound was crystallized as the oxalate salt from acetone to yield 70 mg. (M.p. 142.degree.-143.degree. C.; M.sup.+ : 299; Compound 38).

EXAMPLE 36

A. 3-(3-(3-Ethoxy-1-propoxy)-1,2,5-thiadiazol-4-yl)pyridine

To a solution of 3-ethoxy-1-propanol (940 mg, 9 mmol) and sodium hydride (310 mg, 9 mmol) in dry tetrahydrofuran was added a solution of 3-(3-chloro-1,2,5-thiadiazol-4-yl)pyridine (590 mg, 3 mmol) in dry tetrahydrofuran. The reaction mixture was stirred at room temperature for 2 h. Water was added and the mixture was extracted with ether. The ether phase was dried and evaporated to give the title compound.

B. 3-(3-(3-Ethoxy-1-propoxy)-1,2,5-thiadiazol-4-yl)-1-methylpyridinium iodide

A mixture of methyl iodide (0.5 ml, 9 mmol) and 3-(3-ethoxy-1-propoxy-1,2,5-thiadiazol-4-yl)pyridine (3 mmol) in acetone (5 ml) was stirred at room temperature for 18 h. The title compound precipitated from the solution and was collected by filtration.

C. 3-(3-(3-Ethoxy-1-propoxy)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate

Sodium borohydride (190 mg, 5 mmol) was added to a solution of 3-(3-(3-ethoxy-1-propoxy)-1,2,5-thiadiazol-4-yl)-1-methylpyridinium iodide (3 mmol) in ethanol (99.9%, 15 ml) and the reaction mixture was stirred at -10.degree. C. for 1 h. After evaporation the residue was dissolved in water and extracted with ethyl acetate. The dried organic phases were evaporated and the residue purified by column chromatography (SiO.sub.2, eluent: ethyl acetate/methanol (4:1)). The title compound was crystallized as the oxalate salt from acetone to yield 210 mg. (M.p. 149.degree.-150.degree. C.; M.sup.+ : 283; Compound 39).

EXAMPLE 37

A. 3-(3-(2-Ethoxyethoxy)-1,2,5-thiadiazol-4-yl)pyridine

To a solution of 2-ethoxyethanol (1.08 g, 12 mmol) and sodium hydride (410 mg, 12 mmol) in dry tetrahydrofuran was added a solution of 3-(3-chloro-1,2,5-thiadiazol-4-yl)pyridine (790 mg, 4 mmol) in dry tetrahydrofuran. The mixture was stirred at room temperature for 2 h. Water was added and the mixture was extracted with ether. The ether phase was dried and evaporated to give the title compound.

B. 3-(3-(2-Ethoxyethoxy)-1,2,5-thiadiazol-4-yl)-1-methylpyridinium iodide

A mixture of methyl iodide (0.5 ml, 9 mmol) and 3-(3-(2-ethoxyethoxy)-1,2,5-thiadiazol-4-yl)pyridine (4 mmol) in acetone (3 ml) was stirred at room temperature for 18 h. The title compound precipitated from the solution and was collected by filtration to yield 1.45 g (92%).

C. 3-(3-(2-Ethoxyethoxy)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate

Sodium borohydride (350 mg, 9 mmol) was added to a solution of 3-(3-(2-ethoxyethoxy)-1,2,5-thiadiazol-4-yl)-1-methylpyridinium iodide (1.45 g, 3.7 mmol) in ethanol (99.9%, 15 ml) and the reaction mixture was stirred at -10.degree. C. for 1 h. After evaporation the residue was dissolved in water and extracted with ethyl acetate. The dried organic phases were evaporated and the residue purified by column chromatography (SiO.sub.2, eluent: ethyl acetate/methanol (4:1)). The title compound was crystallized as the oxalate salt from acetone to yield 640 mg. (M.p. 153.degree.-156.degree. C.; M.sup.+ : 269; Compound 40).

EXAMPLE 38

A. 3-(3-(2-Butoxyethoxy)-1,2,5-thiadiazol-4-yl)pyridine

To a solution of 2-butoxyethanol (1.06 g, 9 mmol) and sodium hydride (310 mg, 9 mmol) in dry tetrahydrofuran was added a solution of 3-(3-chloro-1,2,5-thiadiazol-4-yl)pyridine (590 mg, 3 mmol) in dry tetrahydrofuran. The reaction mixture was stirred at room temperature for 2 h. Water was added and the mixture was extracted with ether. The ether phase was dried and evaporated to give the title compound.

B. 3-(3-(2-Butoxyethoxy)-1,2,5-thiadiazol-4-yl)-1-methylpyridinium iodide

A mixture of methyl iodide (0.5 ml, 9 mmol) and 3-(3-(2-butoxyethoxy)-1,2,5-thiadiazol-4-yl)pyridine (3 mmol) in acetone (4 ml) was stirred at room temperature for 18 h. The title compound precipitated from the solution and was collected by filtration to yield 1.07 g (85%).

C. 3-(3-(2-Butoxyethoxy)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate

Sodium borohydride (230 mg, 6 mmol) was added to a solution of 3-(3-(2-butoxyethoxy)-1,2,5-thiadiazol-4-yl)-1-methylpyridinium iodide (1.07 g, 2.5 mmol) in ethanol (99.9%, 20 ml) and the reaction mixture was stirred at -10.degree. C. for 1 h. After evaporation the residue was dissolved in water and extracted with ethyl acetate. The dried organic phases were evaporated and the residue purified by column chromatography (SiO.sub.2, eluent: ethyl acetate/methanol (4:1)). The title compound was crystallized as the oxalate salt from acetone to yield 490 mg. (M.p. 152.degree.-153.degree. C.; M.sup.+ : 297; Compound 41).

EXAMPLE 39

A. 3-(3-(2-(2-Butoxyethoxy)ethoxy)-1,2,5-thiadiazol-4-yl)pyridine

To a solution of 2-(2-butoxyethoxy)ethanol (1.46 g, 9 mmol) and sodium hydride (310 mg, 9 mmol) in dry tetrahydrofuran was added a solution of 3-(3-chloro-1,2,5-thiadiazol-4-yl)pyridine (590 mg, 3 mmol) in dry tetrahydrofuran. The reaction mixture was stirred at room temperature for 1 h. Water was added and the mixture was extracted with ether. The ether phase was dried and evaporated to give the title compound.

B. 3-(3-(2-(2-Butoxyethoxy)ethoxy)-1,2,5-thiadiazol-4-yl)-1-methylpyridiniumiodide

A mixture of methyl iodide (0.5 ml, 9 mmol) and 3-(3-(2-(2-butoxyethoxy)-ethoxy)-1,2,5-thiadiazol-4-yl)pyridine (3 mmol) in acetone (5 ml) was stirred at room temperature for 18 h. The title compound precipitated from the solution and was collected by filtration.

C. 3-(3-(2-(2-Butoxyethoxy)ethoxy)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate

Sodium borohydride (230 mg, 6 mmol) was added to a solution of 3-(3-(2-(2-butoxyethoxy)ethoxy)-1,2,5-thiadiazol-4-yl)-1-methylpyridinium iodide (3 mmol) in ethanol (99.9%, 20 ml) and the reaction mixture was stirred at -10.degree. C. for 1 h. After evaporation the residue was dissolved in water and extracted with ethyl acetate. The dried organic phases were evaporated and the residue purified by column chromatography (SiO.sub.2, eluent: ethyl acetate/methanol (4:1)). The title compound was crystallized as the oxalate salt from acetone to yield 340 mg. (M.p. 90.degree.-91.degree. C.; M.sup.+ : 341; Compound 42).

EXAMPLE 40

A. 3-(3-(2-(2-Ethoxyethoxy)ethoxy)-1,2,5-thiadiazol-4-yl)pyridine

To a solution of 2-(2-ethoxyethoxy)ethanol (1.21 g, 9 mmol) and sodium hydride (310 mg, 9 mmol) in dry tetrahydrofuran was added a solution of 3-(3-chloro-1,2,5-thiadiazol-4-yl)pyridine (590 mg, 3 mmol) in dry tetrahydrofuran. The reaction mixture was stirred at room temperature for 2 h. Water was added and the mixture was extracted with ether. The ether phase was dried and evaporated to give the title compound.

B. 3-(3-(2-(2-Ethoxyethoxy)ethoxy)-1,2,5-thiadiazol-4-yl)-1-methylpyridiniumiodide

A mixture of methyl iodide (0.5 ml, 9 mmol) and 3-(3-(2-(2-ethoxyethoxy)-ethoxy)-1,2,5-thiadiazol-4-yl)pyridine (3 mmol) in acetone (5 ml) was stirred at room temperature for 18 h. The title compound precipitated from the solution and was collected by filtration.

C. 3-(3-(2-(2-Ethoxyethoxy)ethoxy)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate

Sodium borohydride (230 mg, 6 mmol) was added to a solution of 3-(3-(2-(2-ethoxyethoxy)ethoxy)-1,2,5-thiadiazol-4-yl)-1-methylpyridinium iodide (3 mmol) in ethanol (99.9%, 20 ml) and the reaction mixture was stirred at -10.degree. C. for 1 h. After evaporation the residue was dissolved in water and extracted with ethyl acetate. The dried organic phases were evaporated and the residue purified by column chromatography (SiO.sub.2, eluent: ethyl acetate/methanol (4:1)). The title compound was crystallized as the oxalate salt from acetone to yield 290 mg. (M.p. 115.degree.-116.degree. C.; M.sup.+ : 313; Compound 43).

EXAMPLE 41

A. 3-(3-(4-Methylpiperidino)-1,2,5-thiadiazol-4-yl)pyridine

A solution of 3-(3-chloro-1,2,5-thiadiazol-4-yl)pyridine (10.80 g, 4 mmol) and 4-methylpiperidine (1.96 g, 20 mmol) in DMF (10 ml) was heated at 100.degree. C. for 3 h. After evaporation water was added to the residue and extracted with ether. The combined and dried organic phases were evaporated and the residue purified by column chromatography (SiO.sub.2, eluent: ethyl acetate/methylene chloride (1:2)). Yield: 0.8 g (77%).

B. 3-(3-(4-Methylpiperidino)-1,2,5-thiadiazol-4-yl)-1-methylpyridinium iodide

A mixture of methyl iodide (0.5 ml, 8 mmol) and 3-(3-(4-methylpiperidino)-1,2,5-thiadiazol-4-yl)pyridine (0.8 g, 3.1 mmol) in acetone (5 ml) was stirred at room temperature for 18 h. The title compound precipitated from the solution and was collected by filtration to yield 1.14 g (92%).

C. 3-(3-(4-Methylpiperidino)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate

Sodium borohydride (270 mg, 7 mmol) was added to a solution of 3-(3-(4-methylpiperidino)-1,2,5-thiadiazol-4-yl)-1-methylpyridinium iodide (1.14 g, 2.8 mmol) in ethanol (99.9%, 20 ml) and the reaction mixture was stirred at -10.degree. C. for 1 h. After evaporation the residue was dissolved in water and extracted with ethyl acetate. The dried organic phases were evaporated and the residue purified by column chromatography (SiO.sub.2, eluent: ethyl acetate/methanol (4:1)). The title compound was crystallized as the oxalate salt from acetone to yield 450 mg. (M.p. 106.degree.-107.degree. C.; M.sup.+ : 278; Compound 44).

EXAMPLE 42

A. 3-(3-Morpholino-1,2,5-thiadiazol-4-yl)pyridine

A solution of 3-(3-chloro-1,2,5-thiadiazol-4-yl)pyridine (0.59 g, 3 mmol) and morpholine (1.3 g, 15 mmol) in DMF (5 ml) was heated at 100.degree. C. for 3 h. After evaporation water was added to the residue and extracted with ether. The combined and dried organic phases were evaporated and the residue purified by column chromatography (SiO.sub.2, eluent: ethyl acetate/methylene chloride (1:1)). Yield: 0.68 g (91%).

B. 3-(3-Morpholino-1,2,5-thiadiazol-4-yl)-1-methylpyridinium iodide

A mixture of methyl iodide (0.5 ml, 8 mmol) and 3-(3-morpholino-1,2,5-thiadiazol-4-yl)pyridine (680 mg, 2.7 mmol) in acetone (5 ml) was stirred at room temperature for 18 h. The title compound precipitated from the solution and was collected by filtration to yield 1.0 g (94%).

C. 3-(3-Morpholino-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate

Sodium borohydride (380 mg, 10 mmol) was added to a solution of 3-(3-morpholino-1,2,5-thiadiazol-4-yl)-1-methylpyridinium iodide (1.53 g, 39 mmol) in ethanol (99.9%, 30 ml) and the reaction mixture was stirred at -10.degree. C. for 1 h. After evaporation the residue was dissolved in water and extracted with ethyl acetate. The dried organic phases were evaporated and the residue purified by column chromatography (SiO.sub.2, eluent: ethyl acetate/methanol (4:1)). The title compound was crystallized as the oxalate salt from acetone to yield 470 mg. (M.p. 177.degree.-178.degree. C.; M.sup.+ : 266; Compound 45).

EXAMPLE 43

A. 3-(3-Hexylamino-1,2,5-thiadiazol-4-yl)pyridine

A solution of 3-(3-chloro-1,2,5-thiadiazol-4-yl)pyridine (0.59 g, 3 mmol) and hexylamine (1.52 g, 15 mmol) in DMSO (5 ml) was heated at 100.degree. C. for 48 h. After evaporation, water was added to the residue and extracted with ether. The combined organic extracts were dried and evaporated to give the title compound.

B. 3-(3-Hexylamino-1,2,5-thiadiazol-4-yl)-1-methylpyridinium iodide

A mixture of methyl iodide (0.6 ml, 9.6 mmol) and 3-(3-hexylamino-1,2,5-thiadiazol-4-yl)pyridine (3.2 mmol) in acetone (5 ml) was stirred at room temperature for 18 h and evaporated.

C. 3-(3-Hexylamino-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate

Sodium borohydride (380 mg, 10 mmol) was added to a solution of 3-(3-hexylamino-1,2,5-thiadiazol-4-yl)-1-methylpyridinium iodide (4.2 mmol) in ethanol (99.9%, 25 ml) and the reaction mixture was stirred at -10.degree. C. for 1 h. After evaporation the residue was dissolved in water and extracted with ethyl acetate. The dried organic phases were evaporated and the residue purified by column chromatography (SiO.sub.2, eluent: ethyl acetate/methanol (4:1)). The title compound was crystallized as the oxalate salt from acetone to yield 490 mg. (M.p. 102.degree.-103.degree. C.; M.sup.+ : 280; Compound 46).

EXAMPLE 44

A. 3-(3-Propylthio-1,2,5-thiadiazol-4-yl)pyridine

Sodium hydrogen sulfide (220 mg, 3 mmol) was added over 30 min. to a solution of 3-(3-chloro-1,2,5-thiadiazol-4-yl)pyridine (0.59 g, 3 mmol) in DMF (20 ml) at room temperature. Potassium carbonate (1.24 g, 9 mmol) and iodopropan (0.76 g, 4.5 mmol) were added. The reaction mixture was stirred at room temperature for 30 min. Water was added and the mixture extracted with ether. The combined ether phases were dried and evaporated to give the title compound in 89% (0.63 g) yield.

B. 3-(3-Propylthio-1,2,5-thiadiazol-4-yl)-1-methylpyridinium iodide

A mixture of methyl iodide (0.5 ml, 8 mmol) and 3-(3-propylthio-1,2,5thiadiazol-4-yl)pyridine (0.63 g, 2.6 mmol) in acetone (5 ml) was stirred at room temperature for 18 h and evaporated.

C. 3-(3-Propylthio-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate

Sodium borohydride (200 mg, 5 mmol) was added to a solution of 3-(3-propylthio-1,2,5-thiadiazol-4yl)-1-methylpyridinium iodide (2.6 mmol) in ethanol (99.9%, 15 ml) and the reaction mixture was stirred at -10.degree. C. for 1 h. After evaporation the residue was dissolved in water and extracted with ethyl acetate. The dried organic phases were evaporated and the residue purified by column chromatography (SiO.sub.2, eluent: ethyl acetate/methanol (4:1)). The title compound was crystallized as the oxalate salt from acetone to yield 310 mg. (M.p. 138.degree.-139.degree. C.; M.sup.+ : 255; Compound 47).

EXAMPLE 45

A. 3-(3-Butylthio-1,2,5-thiadiazol-4-yl)pyridine

Sodium hydrogen sulfide (0.5 g, 6.8 mmol) was added to a solution of 3-(3-chloro-1,2,5-thiadiazol-4-yl)pyridine (0.5 g, 2.5 mmol) in DMF (20 ml) at room temperature and the reaction mixture was stirred for 30 min. Potassium carbonate (2 g, 14.5 mmol) and butyl iodide (1 ml, 8.8 mmol) were added and the reaction mixture was stirred for additionally 10 min. Water (50 ml) was added and extracted with ether. The combined ether phases were dried and evaporated to give the title compound. Yield: 0.6 g.

B. 3-(3-Butylthio-1,2,5-thiadiazol-4-yl)-1-methylpyridinium iodide

Methyl iodide (1 ml, 15 mmol) was added to a solution of 3-(3-butylthio-1,2,5-thiadiazol-4-yl)pyridine (0.6 g, 2.3 mmol) and the reaction mixture was stirred at room temperature for 48 h and evaporated.

C. 3-(3-Butylthio-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridineoxalate

Sodium borohydride (250 mg, 6.2 mmol) was added to a solution of 3-(3-butylthio-1,2,5thiadiazol-4-yl)-1-methylpyridinium iodide (2.3 mmol) in ethanol (99.9%, 20 ml) and the reaction mixture was stirred at 0.degree. C f.or 1 h. After evaporation the residue was dissolved in water and extracted with ethyl acetate. The dried organic phases were evaporated and the residue purified by column chromatography (SiO.sub.2, eluent: ethyl acetate/methanol (4:1)). The title compound was crystallized as the oxalate salt from acetone to yield 300 mg. (M.p. 148.degree.-150.degree. C.; M.sup.+ : 269; Compound 48).

EXAMPLE 46

A. 3-(3-Methylthio-1,2,5-thiadiazol-4-yl)pyridine

Sodium hydrogen sulfide (0.5 g, 6.8 mmol) was added to a solution of 3-(3-chloro-1,2,5-thiadiazol-4-yl)pyridine (0.5 g, 2.5 mmol) in DMF (20 ml) at room temperature and the reaction mixture was stirred for 30 min. Potassium carbonate (2 g, 14.5 mmol) and methyl iodide (1 ml, 15 mmol) were added and the reaction mixture was stirred for additionally 10 min. Water (50 ml) was added and extracted with ether. The combined ether phases were dried and evaporated to give the title compound. Yield: 0.5 g.

B. 3-(3-Methylthio-1 ,2,5-thiadiazol-4-yl)-1-methylpyridinium iodide

Methyl iodide (1 ml, 15 mmol) was added to a solution of 3-(3-methylthio-1,2,5-thiadiazol-4yl)-pyridine (0.5 g, 2.3 mmol) and the reaction mixture was stirred at room temperature for 48 h and evaporated.

C. 3-(3-Methylthio-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate

Sodium borohydride (250 mg, 6.2 mmol) was added to a solution of 3-(3-methylthio-1,2,5-thiadiazol-4-yl)-1-methylpyridinium iodide (2.3 mmol) in ethanol (99.9%, 20 ml) and the reaction mixture was stirred at 0.degree. C. for 1 h. After evaporation the residue was dissolved in water and extracted with ethyl acetate. The dried organic phases were evaporated and the residue purified by column chromatography (SiO.sub.2, eluent: ethyl acetate/methanol (4:1)). The title compound was crystallized as the oxalate salt from acetone to yield 300 mg. (M.p. 169.degree.-170.degree. C.; M.sup.+ : 227; Compound 49).

EXAMPLE 47

A. Alpha-oximido-3-pyridylacetonitrile

3-pyridylacetonitrile (47.2 g, 400 mmol) was dissolved in a solution of sodium hydroxide (16 9, 400 mmol) in methanol (100 ml). Methylnitrite, generated by dropping a solution of concentrated sulphuric acid (12.8 ml) and water (26 ml) to a solution of sodium nitrite (33.2 9, 480 mmol) in water (20 ml) and methanol (20 ml), was bobled through the 3-pyridylacetonitrile solution at 0.degree. C. The reaction mixture was stirred at 0.degree. C. for 1 h and the precipitate collected by filtration. The precipitate was washed with a little methanol to give the wanted product in 70% (41.1 g) yield. M.sup.+ : 147.

B. Alpha-oximido-3-pyridylacetamidoxime

A mixture of alpha-oximido-3-pyridylacetonitrile (41.0 g, 279 mmol), hydroxylamine hydrochloride (21.5 g, 310 mmol) and sodium acetate (50.8 g, 620 mmol) in ethanol (99.9%, 500 ml) was refluxed for 4 h. After cooling, the precipitate was collected by filtration and dried. The precipitate contained the wanted product and sodium acetate (85 g, 168%); M.sup.+ : 180.

C. 3-(3-Amino-1,2,5-oxadiazol-4-yl)pyridine

Crude alpha-oximido-3-pyridylacetamidoxime (5 g) and phosphorus pentachloride (5 g) was refluxed in dry ether (250 ml) for 6 h. Water and potassium carbonate to alkaline pH was added and the phases separated. The aqueous phase was extracted with ether and the combined ether phases dried. Evaporation of the ether phases gave the title compound in 850 mg yield; M.sup.+ : 162.

D. 3-(3-Amino-1,2,5-oxadiazol-4-yl)-1-methylpyridinium iodide

To a solution of 3-(3-amino-1,2,5-oxadiazol-4-yl)pyridine (870 mg, 5.3 mmol) in acetone (20 ml) was added methyl iodide (990 .mu.l, 16 mmol) and the reaction mixture was stirred overnight at room temperature. The title compound precipitated and was collected by filtration (1.1 g, 69%).

E. 3-(3-Amino-1,2,5oxadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate

Sodium borohydride (262 mg, 6.9 mmol) was added to a solution of 3-(3-amino-1,2,5-oxadiazol-4-yl)-1-methylpyridinium iodide (1.05 g, 3.45 mmol) in methanol (80 ml) at 0.degree. C. After 15 min. water (40 ml) was added and the mixture extracted with ether. The ether phase was dried, evaporated and purified by column chromatography (eluent: ethyl acetate:methanol (2:1)). Crystallization from acetone with oxalic acid gave the title compound in 310 mg (50%) yield. (M.p. 181.degree.-183.degree. C.; M.sup.+ : 180; Compound 50).

EXAMPLE 48

A. 3-(3-Acetylamino-1,2,5-oxadiazol-4-yl)pyridine

Crude hydroxyimino-3-pyridylmethylamidoxime (4.5 g) and polyphosphoric acid (49 g) was stirred at 100.degree. C. for 18 h. After cooling to room temperature aqueous ammonia (25%) was added slowly to pH>9 and the precipitate collected by filtration. The precipitate was dissolved in water and extracted with methylene chloride. The organic phases were dried and evaporated to give the title compound in 430 mg yield.

B. 3-(3-Acetylamino-1,2,5-oxadiazol-4-yl)-1-methylpyridinium iodide

Methyl iodide (450 .mu.l, 7.2 mmol) was added to a solution of 3-(3-acetyl-amino-1,2,5-oxadiazol-4-yl)pyridine (490 mg, 2.4 mmol) in acetone. The reaction mixture was stirred at room temperature for 18 h and the predipitate collected by filtration. Yield: 640 mg (77%).

C. 3-(3-Acetylamino-1,2,5-oxadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate

Sodium borohydride (140 mg, 3.7 mmol) was added to a solution of 3-(3-acetylamino-1,2,5-oxadiazol-4-yl)-1-methylpyridinium iodide (640 mg, 1.85 mmol) in methanol (15 ml) at 0.degree. C. After 15 min. water (10 ml) was added and the reaction mixture extracted with ether. The combined ether phases were dried and evaporated. Crystallization from acetone with oxalic acid gave the title compound in 140 mg yield. (M.p. 180.degree.-184.degree. C.; M.sup.+ : 222; Compound 51).

EXAMPLE 49

A. 3-(1,2,5-Oxadiazol-3-yl)pyridine and 3-(3-chloro-1,2,5-oxadiazol-4-yl)pyridine

To a solution of 3-(3-amino-1,2,5-oxadiazol-4-yl)pyridine (1.0 g, 6.2 mmol) in glacial acetic acid (16 ml) and concentrated hydrochloric acid (5.2 ml) was added CuCl.sub.2 (938 mg, 7 mmol) and cupper coils (100 mg) at 0.degree. C. After 10 min. a solution of sodium nitrite (483 mg, 7 mmol) in water (3 ml) was added dropwise at 5.degree. C. The reaction mixture was stirred additionally 30 min. at 0.degree. C. Aqueous sodium hydroxide (2N) was added to alkaline pH and the mixture extracted with ether. The ether phases were dried and evaporated to give a mixture of the title compounds. Separation by column chromatography (SiO.sub.2, eluent: ethyl acetate) gave the chloro compound, upper spot, in 230 mg yield, and the unsubstituted product, lower spot, in 60 mg yield.

B. 3-(3-Chloro-1,2,5-oxadiazol-4-yl)-1-methylpyridinium iodide

Methyl iodide (1 ml, 15 mmol) was added to a solution of 3-(3-chloro-1,2,5-oxadiazol-4-yl)pyridine (230 mg, 1.2 mmol) in acetone. The reaction mixture was stirred at room temperature for 18 h and evaporated to give the title compound.

C. 3-(3-Chloro-1,2,5-oxadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate

Sodium borohydride (119 mg, 3.2 mmol) was added to a solution of 3-(3-chloro-1,2,5-oxadiazol-4-yl)-1-methylpyridinium iodide (1.2 mmol) in methanol (5 ml) at 0.degree. C. After 15 min. water was added and the mixture extracted with ether. The ether phases were dried and evaporated. Crystallization from acetone with oxalic acid and recrystallization from acetone gave the title compound in 60 mg yield. (M.p. 126.degree.-129.degree. C.; M.sup.+ : 198 and 200; Compound 52).

EXAMPLE 50

A. 3-(1,2,5-Oxadiazol-3-yl)-1-methylpyridinium iodide

Methyl iodide (1 ml, 15 mmol) was added to a solution of 3-(1,2,5-oxadiazol-3-yl)pyridine (430 mg, 2.9 mmol) in acetone (20 ml). The reaction mixture was stirred at room temperature for 18 h. The product precipitated from the solution and the title compound was collected by filtration in 82% (700 mg) yield.

B. 3-(1,2,5-Oxadiazol-3-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate

Sodium borohydride (168 mg, 4.4 mmol) was added to a solution of 3-(1,2,5-oxadiazol-3-yl)-1-methylpyridinium iodide (640 mg, 2.2 mmol) in methanol (15 ml) and water (2 ml) at 0.degree. C. After 15 min. water was added and the mixture extracted with ether. The combined ether phases were dried and evaporated. The residue was crystallized as the oxalate salt from acetone giving the title compound in 100 mg yield. (M.p. 238.degree.-240.degree. C. dec.; M.sup.+ : 165; Compound 53).

EXAMPLE 51

A. 3-(3-Hexyloxy-1,2,5-oxadiazol-4-yl)pyridine

To a solution of sodium (100 mg, 4.3 mmol) in 1-hexanol (10 ml) was added 3-(3-chloro-1,2,5-oxadiazol-4-yl)pyridine (180 mg, 1 mmol). The mixture was stirred at 25.degree. C. for 18 h and evaporated. The residue was dissolved in water and extracted with ether. The combined organic phases were dried and evaporated to give the title compound.

B. 3-(3-Hexyloxy-1,2,5-oxadiazol-4-yl)-1-methylpyridinium iodide

A mixture of methyl iodide (1 ml, 15 mmol) and 3-(3-hexyloxy-1,2,5-oxadiazol-4-yl)pyridine (1 mmol) in acetone (5 ml) was stirred at room temperature for 18 h and evaporated to give the title compound.

C. 3-(3-Hexyloxy-1,2,5-oxadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate

Sodium borohydride (76 mg, 2 mmol) was added to a solution of 3-(3-hexyloxy-1,2,5-oxadiazol-4-yl)-1-methylpyridinium iodide (1 mmol) in methanol (5 ml) and the reaction mixture was stirred at 0.degree. C. for 15 min. After evaporation the residue was dissolved in water and extracted with ether. The dried organic phases were evaporated and the residue purified by column chromatography (SiO.sub.2, eluent: ethyl acetate/methanol (4:1)). The title compound was crystallized as the oxalate salt from acetone to yield 60 mg. (M.p. 143.degree.-147.degree. C.; M.sup.+ : 265; Compound 54).

EXAMPLE 52

A. 3-(3-Butyloxy-1,2,5-oxadiazol-4-yl)pyridine

To a solution of sodium (150 mg, 6.5 mmol) in 1-butanol (5 ml) was added 3-(3-chloro-1,2,5-oxadiazol-4-yl)pyridine (350 mg, 1.9 mmol). The mixture was stirred at 25.degree. C. for 2 h and evaporated. The residue was dissolved in water and extracted with ether. The combined organic phases were dried and evaporated to give the title compound.

B. 3-(3-Butyloxy-1,2,5-oxadiazol-4-yl)-1-methylpyridinium iodide

A mixture of methyl iodide (1 ml, 15 mmol) and 3-(3-butyloxy-1,2,5-oxadiazol-4-yl)pyridine (1.9 mmol) in acetone (10 ml) was stirred at room temperature for 18 h and evaporated.

C. 3-(3-Butyloxy-1,2,5-oxadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate

Sodium borohydride (148 mg, 3.8 mmol) was added to a solution of 3-(3-butyioxy-1,2,5-oxadiazol-4-yl)-1-methylpyridinium iodide (1.9 mmol) in methanol (20 ml) and the reaction mixture was stirred at 0.degree. C. for 15 min. After evaporation the residue was dissolved in water and extracted with ether. The dried organic phases were evaporated and the residue purified by column chromatography (SiO.sub.2, eluent: ethyl acetate/methanol (4:1)). The title compound was crystallized as the oxalate salt from acetone to yield 120 mg. (M.p. 132.degree.-135.degree. C.; M.sup.+ : 237; Compound 55).

EXAMPLE 53

A. 3-(3-(3-Hexynyloxy)-1,2,5-oxadiazol-4-yl)pyridine

To a solution of 3-hexyn-1-ol (980 mg, 10 mmol) and sodium hydride (240 mg, 10 mmol) in dry tetrahydrofuran was added a solution of 3-(3-chloro-1,2,5-oxadiazol-4-yl)pyridine (450 mg, 2.5 mmol) in dry tetrahydrofuran. The reaction mixture was stirred at room temperature for 2 h. Water was added and the mixture was extracted with ether. The. ether phase was dried and evaporated to give the title compound.

B. 3-(3-(3-Hexynyloxy)-1,2,5-oxadiazol-4-yl)-1-methylpyridinium iodide

A mixture of methyl iodide (1.5 ml, 22 mmol) and 3-(3-(3-hexynyloxy)-1,2,5-oxadiazol-4-yl)pyridine (2.5 mmol) in acetone (20 ml) was stirred at room temperature for 18 h and evaporated to give the title compound.

C. 3-(3-(3-Hexynyloxy)-1,2,5-oxadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate

Sodium borohydride (190 mg, 5 mmol) was added to a solution of 3-(3-(3-hexynyloxy)-1,2,5-oxadiazol-4-yl)-1-methylpyridinium iodide (2.5 mmol) in methanol (20 ml) and the reaction mixture was stirred at 0.degree. C. for 15 min. After evaporation the residue was dissolved in water and extracted with ether. The dried organic phases were evaporated and the residue purified by column chromatography (SiO.sub.2, eluent: ethyl acetate/methanol (4:1)). The title compound was crystallized as the oxalate salt from acetone to yield 50 mg. (M.p. 159.degree.-161.degree. C.; M.sup.+ : 261; Compound 56).

EXAMPLE 54

3-(3-Pentyl-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridinium oxalate

To a solution of 3-(3-chloro-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine (450 mg, 1.5 mmol) in tetrahydrofuran (20 ml) was added slowly a solution of pentylmagnesium bromide (1.5 mmol) in tetrahydrofuran at 0.degree. C. The reaction mixture was stirred for 10 min. and water (20 ml) was added. The product was extracted with ether (3.times.100 ml) and the dried ether phases evaporated. The residue was crystallized as the oxalate salt from acetone in 300 mg (58%) yield. Recrystallization from ethanol gave the title compound in 125 mg (24%) yield. (M.p. 156.degree.-157.degree. C.; M.sup.+ : 251; Compound 57).

EXAMPLE 55

3-(3-Heptyl-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridinium oxalate

To a solution of 3-(3-chloro-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine (450 mg, 1.5 mmol) in tetrahydrofuran (20 ml) was added slowly a solution of heptylmagnesium bromide (1.5 mmol) in tetrahydrofuran at 0.degree. C. The reaction mixture was stirred for 10 min. and water (20 ml) was added. The product was extracted with ether (3.times.100 ml) and the dried ether phases evaporated. The residue was crystallized as the oxalate salt from acetone in 400 mg (73%) yield. (M.p. 151.degree.-152.degree. C.; M.sup.+ : 274; Compound 58).

EXAMPLE 56

3-(3-(5-Hexenyl)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridinium oxalate

To a solution of 3-(3-chloro-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine (450 mg, 1.5 mmol) in tetrahydrofuran (20 ml) was added slowly a solution of 5-hexenylmagnesium bromide (1.5 mmol) in tetrahydrofuran at 0.degree. C. The reaction mixture was stirred for 10 min. and water (20 ml) was added. The product was extracted with ether (3.times.100 ml) and the dried ether phases evaporated. The residue was purified by column chromatography (SiO.sub.2, eluent: ethyl acetate/methanol (4:1)). The title compound was crystallized as the oxalate salt from acetone in 340 mg (64%) yield. (M.p. 113.degree.-115.degree. C.; M.sup.+ : 263; Compound 59).

EXAMPLE 57

3-(3-Octyl-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridinium oxalate

To a solution of 3-(3-chloro-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine (450 mg, 1.5 mmol) in tetrahydrofuran (20 ml) was added slowly a solution of octylmagnesium bromide (1.5 mmol) in tetrahydrofuran at 0.degree. C. The reaction mixture was stirred for 10 min. and water (20 ml) was added. The product was extracted with ether (3.times.100 ml) and the dried ether phases evaporated. The residue was purified by column chromatography (SiO.sub.2, eluent: ethyl acetate/methanol (4:1)). The title compound was crystallized as the oxalate salt from acetone in 430 mg (75%) yield. (M.p. 157.degree.-158.degree. C.; M.sup.+ : 293; Compound 60).

EXAMPLE 58

3-(3-Isobutyl-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridinium oxalate

To a solution of 3-(3-chloro-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine (300 mg, 1.5 mmol) in tetrahydrofuran (20 ml) was added slowly a solution of isobutylmagnesium bromide (1.5 mmol) in tetrahydrofuran at 0.degree. C. The reaction mixture was stirred for 10 min. and water (20 ml) was added. The product was extracted with ether (3.times.100 ml) and the dried ether phases evaporated. The residue was purified by column chromatography (SiO.sub.2, eluent: ethyl acetatae/methanol (4:1)). The title compound was crystallized as the oxalate salt from acetone in 350 mg (76%) yield. (M.p. 148.degree.-149.degree. C.; M.sup.+ : 237; Compound 61).

EXAMPLE 59

3-(3-Cyclopropylmethyl-1,2,5-thiadiazol-4-yl)-1 ,2,5,6-tetrahydro-1 -methylpyridinium oxalate

To a solution of 3-(3-chloro-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine (300 mg, 1.4 mmol) in tetrahydrofuran (20 ml) was added slowly a solution of cyclopropylmethylmagnesium bromide (1.5 mmol) in tetrahydrofuran at 0.degree. C. The reaction mixture was stirred for 10 min. and water (20 ml) was added. The product was extracted with ether (3.times.100 ml) and the dried ether phases evaporated. The residue was purified by column chromatography (SiO.sub.2, eluent: ethyl acetate/methanol (4:1)). The title compound was crystallized as the oxalate salt from acetone in 380 mg (83%) yield. (M.p. 147.degree.-148.degree. C.; M.sup.+ : 235; Compound 62).

EXAMPLE 60

3-(3-Propyl-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridinium oxalate

To a solution of 3-(3-chloro-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylyridine (450 mg, 1.5 mmol) in tetrahydrofuran (20 ml) was added slowly a solution of propylmagnesium bromide (1.5 mmol) in tetrahydrofuran at 0.degree. C. The reaction mixture was stirred for 10 min. and water (20 ml) was added. The product was extracted with ether (3.times.100 ml) and the dried ether phases evaporated. The residue was crystallized as the oxalate salt from acetone in 350 mg (75%) yield. (M.p. 141.degree.-142.degree. C.; M.sup.+ : 223; Compound 63).

EXAMPLE 61

A. 3-(3-Octylthio-1,2,5-thiadiazol-4-yl)pyridine

Sodium hydrogen sulfide (0.25 g, 3.3 mmol) was added to a solution of 3-(3-chloro-1,2,5-thiadiazol-4-yl)pyridine (0.59 g, 3 mmol) in DMF (20 ml) at room temperature and the reaction mixture was stirred for 30 min. Potassium carbonate (1.24 g, 9 mmol) and 1-bromooctane (0.80 ml, 4.5 mmol) were added and the reaction mixture was stirred for additionally 10 min. Water (50 ml) was added and extracted with ether. The combined ether phases were dried and evaporated to give the title compound.

B. 3-(3-Octylthio-1,2,5-thiadiazol-4-yl)-1-methylpyridinium iodide

Methyl iodide (0.5 ml, 7.5 mmol) was added to a solution of 3-(3-octylthio-1,2,5-thiadiazol-4-yl)pyridine (3 mmol) and the reaction mixture was stirred at room temperature for 48 h and evaporated.

C. 3-(3-Octylthio-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridineoxalate

Sodium borohydride (270 mg, 7 mmol) was added to a solution of 3-(3-octylthio-1,2,5-thiadiazol-4-yl)-1-methylpyridinium iodide (3 mmol) in ethanol (99.9%, 20 ml) and the reaction mixture was stirred at 0.degree. C. for 1 h. After evaporation the residue was dissolved in water and extracted with ethyl acetate. The dried organic phases were evaporated and the residue purified by column chromatography (SiO.sub.2, eluent: ethyl acetate/methanol (4:1)). The title compound was crystallized as the oxalate salt from acetone to yield 400 mg. (M.p. 121.degree.-122.degree. C.; M.sup.+ : 325; Compound 64).

EXAMPLE 62

A. 3-(3-Ethylthio-1,2,5-thiadiazol-4-yl)pyridine

Sodium hydrogen sulfide (0.25 g, 3.3 mmol) was added to a solution of 3-(3-chloro-1,2,5-thiadiazol-4-yl)pyridine (0.59 g, 3 mmol) in DMF (20 ml) at room temperature and the reaction mixture was stirred for 30 min. Potassium carbonate (1.24 g, 9 mmol) and ethyl iodide (0.36 ml, 4.5 mmol) were added and the reaction mixture was stirred for additionally 10 min. Water (50 ml) was added and extracted with ether. The combined ether phases were dried and evaporated to give the title compound.

B. 3-(3-Ethylthio-1,2,5-thiadiazol-4-yl)-1-methylpyridinium iodide

Methyl iodide (0.5 ml, 7.5 mmol) was added to a solution of 3-(3-ethylthio-1,2,5-thiadiazol-4-yl)pyridine (3 mmol) and the reaction mixture was stirred at room temperature for 48 h and evaporated.

C. 3-(3-Ethylthio-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridineoxalate

Sodium borohydride (270 mg, 7 mmol) was added to a solution of 3-(3-ethylthio-1,2,5-thiadiazol-4-yl)-1-methylpyridinium iodide (3 mmol) in ethanol (99.9%, 20 ml) and the reaction mixture was stirred at 0.degree. C. for 1 h. After evaporation the residue was dissolved in water and extracted with ethyl acetate. The dried organic phases were evaporated and the residue purified by column chromatography (SiO.sub.2, eluent: ethyl acetate/methanol (4:1)). The title compound was crystallized as the oxalate salt from acetone to yield 490 mg. (M.p. 145.degree.-146.degree. C.; M.sup.+ : 241; Compound 65).

EXAMPLE 63

A. 3-(3-Pentylthio-1,2,5-thiadiazol-4-yl)pyridine

Sodium hydrogen sulfide (0.25 g, 3.3 mmol) was added to a solution of 3-(3-chloro-1,2,5-thiadiazol-4-yl)pyridine (0.59 9, 3 mmol) in DMF (20 ml) at room temperature and the reaction mixture was stirred for 30 min. Potassium carbonate (1.24 g, 9 mmol) and pentyl bromide (700 mg, 4.5 mmol) were added and the reaction mixture was stirred for additionally 10 min. Water (50 ml) was added and extracted with ether. The combined ether phases were dried and evaporated to give the title compound.

B. 3-(3-Pentylthio-1,2,5-thiadiazol-4-yl)-1-methylpyridinium iodide

Methyl iodide (0.5 ml, 7.5 mmol) was added to a solution of 3-(3-pentylthio-1,2,5-thiadiazol-4-yl)pyridine (3 mmol) and the reaction mixture was stirred at room temperature for 48 h and evaporated.

C. 3-(3-Pentylthio-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate

Sodium borohydride (300 mg, 8 mmol) was added to a solution of 3-(3-pentylthio-1,2,5-thiadiazol-4-yl)-1-methylpyridinium iodide (3 mmol) in ethanol (99.9%, 20 ml) and the reaction mixture was stirred at 0.degree. C. for 1 h. After evaporation the residue was dissolved in water and extracted with ethyl acetate. The dried organic phases were evaporated and the residue purified by column chromatography (SiO.sub.2, eluent: ethyl acetate/methanol (4:1)). The title compound was crystallized as the oxalate salt from acetone to yield 430 mg. (M.p. 136.degree.-138.degree. C.; M.sup.+ : 283; Compound 66).

EXAMPLE 64

A. 3-(3-Hexylthio-1,2,5-thiadiazol-4-yl)pyridine

Sodium hydrogen sulfide (0.25 g, 3.3 mmol) was added to a solution of 3-(3-chloro-1,2,5-thiadiazol-4-yl)pyridine (0.59 g, 3 mmol) in DMF (20 ml) at room temperature and the reaction mixture was stirred for 30 min. Potassium carbonate (1.24 g, 9 mmol) and hexyl bromide (0.63 ml, 4.5 mmol) were added and the reaction mixture was stirred for additionally 10 min. Water (50 ml) was added and extracted with ether. The combined ether phases were dried and evaporated to give the title compound.

B. 3-(3-Hexylthio-1,2,5-thiadiazol-4-yl)-1-methylpyridinium iodide

Methyl iodide (1 ml, 15 mmol) was added to a solution of 3-(3-hexylthio-1,2,5-thiadiazol-4-yl)pyridine (3 mmol) and the reaction mixture was stirred at room temperature for 48 h and evaporated.

C. 3-(3-Hexylthio-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridineoxalate

Sodium borohydride (230 mg, 6 mmol) was added to a solution of 3-(3-hexylthio-1,2,5-thiadiazol-4-yl)-1-methylpyridinium iodide (3 mmol) in ethanol (99.9%, 20 ml) and the reaction mixture was stirred at 0.degree. C. for 1 h. After evaporation the residue was dissolved in water and extracted with ethyl acetate. The dried organic phases were evaporated and the residue purified by column chromatography (SiO.sub.2, eluent: ethyl acetate/methanol (4:1)). The title compound was crystallized as the oxalate salt from acetone to yield 350 mg. (M.p. 126.degree.-127.degree. C.; M.sup.+ : 297; Compound 67).

EXAMPLE 65

A. 3-(3-(5-Cyanopentylthio)-1,2,5-thiadiazol-4-yl)pyridine

Sodium hydrogen sulfide monohydrate (0.25 g, 3.3 mmol) was added to a solution of 3-(3-chloro-1,2,5-thiadiazol-4-yl)pyridine (0.59 g, 3.0 mmol) in DMF (20 ml) at room temperature and the reaction mixture was stirred for 1 h. Potassium carbonate (1.24 g, 9 mmol) and 6-bromocapronitrile (0.80 g, 4.5 mmol) were added and the reaction mixture was stirred for additionally 24 h. Water (50 ml) was added and extracted with ether. The combined ether phases were dried and evaporated to give the title compound.

B. 3-(3-(5-Cyanopentylthio)-1,2,5-thiadiazol-4-yl)-1-methylpyridinium iodide

Methyl iodide (1 ml, 15 mmol) was added to a solution of 3-(3-(5-cyanopentylthio)-1,2,5-thiadiazol-4-yl)pyridine (3 mmol) in acetone and the reaction mixture was stirred at room temperature for 20 h. and evaporated.

C. 3-(3-(5-Cyanopentylthio)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate

Sodium borohydride (290 mg, 7.5 mmol) was added to a solution of 3-(3-(5-cyanopentylthio)-1,2,5-thiadiazol-4-yl)-1-methylpyridinium iodide (3 mmol) in ethanol (99.9%, 20 ml) and the reaction mixture was stirred at -10.degree. C. for 1 h. After evaporation the residue was dissolved in water and extracted with ethyl acetate. The dried organic phases were evaporated and the residue purified by column chromatography (SiO.sub.2, eluent: ethyl acetate/methanol (4:1)). The title compound was crystallized as the oxalate salt from acetone to yield 410 mg. M.p. 139.degree.-140.degree. C. Compound 68.

The following compounds were made in exactly the same manner, starting with the appropriate alkyl halogenide:

3-(3-(3-Chloropropylthio)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate. M.p. 136.degree.-138.degree. C. Compound 69.

3-(3-(3-Cyanopropylthio)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate. M.p. 117.5.degree.-118.degree. C. Compound 70.

3-(3-(3-Phenylpropylthio)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate. M.p. 110.degree.-110.5.degree. C. Compound 71.

3-(3-(2-Phenoxyethylthio)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate. M.p. 125.5.degree.-126.degree. C. Compound 72.

3-(3-(4-Cyanobutylthio)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate. M.p. 127.degree.-127.5.degree. C. Compound 73.

3-(3-(8-Hydroxyoctylthio)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate. M.p. 112.5.degree.-113.5.degree. C. Compound 74.

3-(3-(4-Chlorobutylthio)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate. M.p. 136.degree.-137.degree. C. Compound 75.

3-(3-(4,4-Bis-(4-fluorophenyl)-butylthio)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate. M.p. 117.5.degree.-118.degree. C. Compound 76.

3-(3-(2-(1,3-Dioxolane-2-yl)-ethylthio)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate. M.p. 117.degree.-118.degree. C. Compound 77.

3-(3-(4-Cyanobenzylthio)-1,2,5thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate. M.p. 138.degree.-140.degree. C. Compound 78.

3-(3-(2-Phenylethylthio)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate. M.p. 155.degree.-156.degree. C. Compound 79.

3-(3-(4-Bromobenzylthio)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate. M.p. 139.degree.-140.degree. C. Compound 80.

3-(3-(4-Methylbenzylthio)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate. M.p. 162.degree.-165.degree. C. Compound 81.

3-(3-(4-Pyridylmethylthio)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate. M.p. 140.degree.-142.degree. C. Compound 82.

3-(3-(2-Benzoylethylthio)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate. M.p. 99.degree.-100.degree. C. Compound 83.

3-(3-(4-Oxo-4-(4-fluorophenyl)-butylthio)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate. M.p. 131.degree.-132.degree. C. Compound 84.

3-(3-Benzyloxycarbonylmethylthio-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate. M.p. 179.degree.-180.degree. C. Compound 85.

3-(3-Benzylthio-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate. M.p. 195.degree.-197.degree. C. Compound 86.

3-(3-(4,4,4-Trifluorobutylthio)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpiperidine oxalate. M.p. 163.degree.-165.degree. C. Compound 87.

3-(3-(5,5,5-Trifluoropentylthio)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate. M.p. 134.degree.-136.degree. C. Compound 88.

3-(3-(6,6,6-Trifluorohexylthio)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate. M.p. 128.degree.-129.degree. C. Compound 89.

3-(3-Ethoxycarbonylpentylthio-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate. M.p. 78.degree.-81.degree. C. Compound 90.

3-(3-(2,2,2-Trifluoroethylthio)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate. M.p. 159.degree.-163.degree. C. Compound 225.

3-(3-Isohexylthio-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate. M.p. 131.degree.-134.degree. C. Compound 226.

3-(3-Ethoxycarbonylpropylthio-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine hydrochloride. M.p. 109.degree.-111.degree. C. Compound 227.

3-(3-(2-(2-Thienylthio)ethylthio))-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate. M.p. 112.degree.-115.degree. C. Compound 228.

3-(3-(5-Ethyl-2-thienylmethylthio) -1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate. M.p. 106.degree.-110.degree. C. Compound 229.

3-(3-(6-Hydroxyhexylthio)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methyl-pyridine oxalate. M.p. 108.degree.-110.degree. C. Compound 230.

3-(3-(3-Methyl-2-thienylmethylthio)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate. M.p. 184.degree.-186.degree. C. Compound 231.

3-(3-(2-(2-Thienylthio)propylthio))-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate. M.p. 193.degree.-196.degree. C. Compound 232.

3-(3-(4-Ethoxy-1,2,5-thiadiazol-3-ylthio)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate. M.p. 173.degree.-174.degree. C. Compound 233.

3-(3-(5-Methyl-2-thienylmethylthio)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate. M.p. 148.degree.-149.degree. C. Compound 234.

3-(3-(4-Ethylthio-1,2,5-thiadiazol-3-ylthio)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate. M.p. 187.degree.-189.degree. C. Compound 235.

3-(3-(4-Butylthio-1,2,5-thiadiazol-3-ylthio)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate. M.p. 162.degree.-164.degree. C. Compound 236.

3-(3-(4-Propoxy-1,2,5-thiadiazol-3-ylthio)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate. M.p. 182.degree.-183.degree. C. Compound 237.

cis 3-(3-(3-Hexenylthio)-1,2,5-thiadiazol-4-yl)-1,2,5,6tetrahydro-1-methylpyridine oxalate. M.p. 101.degree.-102.degree. C. Compound 238.

3-(3-(1-Cyclopropylmethylthio)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate. M.p. 145.degree.-146.degree. C. Compound 239.

3-(3-(1-Ethoxycarbonylpentylthio)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate. M.p. 94.degree.-95.degree. C. Compound 240.

3-(3-(5-Hexenylthio)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate. M.p. 115.degree.-116.degree. C. Compound 241.

3-(3-Cyclopentylthio-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate. M.p. 144.degree.-145.degree. C. Compound 242.

3-(3-(2-Methoxyethylthio)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methyl-pyridine oxalate. M.p. 150.degree.-151.degree. C. Compound 243.

3-(3-(2-(2-Ethoxymethoxy)-ethylthio)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate. M.p. 117.degree.-118.degree. C. Compound 244.

3-(3-(4-Pentynylthio)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate. M.p. 121.degree.-122.degree. C. Compound 245.

3-(3-Heptylthio-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate. M.p. 122.degree.-123.degree. C. Compound 246.

3-(3-(2-Ethylbutylthio)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate. M.p. 141.degree.-142.degree. C. Compound 247.

3-(3-Cyclohexylmethylthio-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate. M.p. 153.degree.-155.degree. C. Compound 248.

3-(3-(7-Octenylthio)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate. M.p. 115.degree.-116.degree. C. Compound 249.

3-(3-(3-Butenylthio)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate. M.p. 140.degree.-141.degree. C. Compound 250.

3-(3-(4-Pentenylthio)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate. M.p. 137.degree.-138.degree. C. Compound 251.

3-(3-(3,3,3-Trifluoropropylthio)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate. M.p. 131.degree.-135.degree. C. Compound 252.

3-(3-(1-Oxo-1-phenylpropylthio-1,2,5-thiadiazol-4-yl)-1 ,2,5,6-tetrahydro-1-methylpyridine oxalate. M.p. 99.degree.-100.degree. C. Compound 253.

3-(3-(4-Phenylthiobutylthio)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate. M.p. 97.degree.-99.degree. C. Compound 254.

3-(3-Cyanomethylthio-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate. M.p. 176.degree.-177.degree. C. Compound 255.

3-(3-(6-Chlorohexylthio)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate. M.p. 125.degree.-126.degree. C. Compound 256.

3-(3-(5-Chloropentylthio)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate. M.p. 106.degree.-107.degree. C. Compound 257.

EXAMPLE 66

A. 3-(3-(6,6,6-Trifluorohexyloxy-1,2,5-thiadiazol-4-yl)pyridine

To a mixture of sodium hydride (12.8 mmol) and 6,6,6-trifluoro-1-hexanol (3.0 g, 19.2 mmol) in tetrahydrofuran (40 ml) was added 3-(3-chloro-1,2,5-thiadiazol-4-yl)pyridine (1.3 g, 6.4 mmol). The mixture was refluxed for 36 h. and evaporated. After evaporation the residue was dissolved in water then extracted with diethyl ether. The dried organic phases were evaporated and the residue purified by column chromatography (silica gel, eluent: ethyl acetate/hexanes) to yield 630 mg (31%) of the title compound.

B. 3-(3-(6,6,6-Trifluorohexyloxy-1,2,5-thiadiazol-4-yl)-1-methylpyridinium iodide

A solution of methyl iodide (852 mg, 6.0 mmol) and 3-(3-(6,6,6-trifluorohexyloxy-1,2,5-thiadiazol-4-yl)pyridine (630 mg, 2.0 mmol) in acetone (25 ml) was refluxed for 7 h. The solution was evaporated and the residue was used directly in the next step.

C. 1,2,5,6-Tetrahydro-1-methyl-3-(3-(6,6,6-trifluorohexyloxy)-1,2,5-thiadiazol-4-yl)pyridine oxalate

Sodium borohydride (380 mg, 10 mmol) was added to a solution of 3-(3-(6,6,6-trifluorohexyloxy-1,2,5-thiadiazol-4-yl)-1-methylpyridinium iodide (2.0 mmol) in ethanol (15 ml) and the reaction mixture was stirred at room temperature overnight. After evaporation the residue was dissolved in water and extracted with diethyl ether. The dried organic phases were evaporated and the residue was purified by column chromatography (silica gel, eluent: 25% ethyl acetate in hexanes). The title compound was crystallized as the oxalate salt from acetone to yield 180 mg (21%) M.p. 138.degree.-140.degree. C. Theoretical % C=45.17, % H=5.21, % N=9.88. Found % C=45.13, % H=5.18, % N 9.62. Compound 91.

The following compounds were made in exactly the same manner using the appropriate alkoxy derivative:

1,2,5,6-Tetrahydro-1-methyl-3-(3-(3-(2-thienyl)-1-propoxy)-1,2,5-thiadiazol-4-yl)pyridine oxalate M.p. 130.degree.-133.degree. C., M.sup.+ : 321. Compound 92.

1,2,5,6-Tetrahydro-1-methyl-3-(3-(3-(4-methoxyphenyl)-1-propoxy)-1,2,5-thiadiazol-4-yl)pyridine oxalate M.p. 166.degree.-167.degree. C., M.sup.+ : 345. Compound 93.

1,2,5,6-Tetrahydro-1-methyl-3-(3-(2-(4-methoxyphenyl)-1-ethoxy) -1,2,5-thiadiazol-4-yl)pyridine oxalate M.p. 166.degree.-167.degree. C., M.sup.+ : 331. Compound 94.

1,2,5,6-Tetrahydro-1-methyl-3-(3-(2-(2-thienyl)-1-ethoxy)-1,2,5-thiadiazol-4-yl)pyridine oxalate. M.p. 145.degree.-146.degree. C., M.sup.+ : 306. Compound 95.

1,2,5,6-Tetrahydro-1-methyl-3-(3-(2-(3-thienyl)-1-ethoxy)-1,2,5-thiadiazol-4-yl)pyridine oxalate. M.p. 138.degree.-140.degree. C., M.sup.+ : 306. Compound 96.

1,2,5,6-Tetrahydro-1-methyl-3-(3-(3-hydroxy-1-propoxy)-1,2,5-thiadiazol-4-yl)pyridine oxalate. M.p. 105.degree.-107.degree. C., M.sup.+ : 256. Compound 97.

1,2,5,6-Tetrahydro-1-methyl-3-(3-(2-phenyl-1-ethoxy) -1,2,5-thiadiazol-4-yl)pyridine oxalate. M.p. 146.degree.-147.degree. C., M.sup.+ : 301. Compound 98.

1,2,5,6-Tetrahydro-1-methyl-3-(3-(2-thienylmethoxy)-1,2,5-thiadiazol-4-yl)pyridine oxalate. M.p. 161.degree.-162.degree. C., M.sup.+ : 294. Compound 99.

1,2,5,6-Tetrahydro-1-methyl-3-(3-(3-hydroxy-1-hexyloxy)-1,2,5-thiadiazol-4-yl)pyridine oxalate. M.p. 147.degree.-148.degree. C., M.sup.+ : 297. Compound 100.

1,2,5,6-Tetrahydro-1-methyl-3-(3-(3thienylmethoxy) -1,2,5-thiadiazol-4-yl)pyridine oxalate. M.p. 175.degree.-176.degree. C., M.sup.+ : 293. Compound 101.

1,2,5,6-Tetrahydro-1-methyl-3-(3-(3-phenyl-1-propoxy)-1,2,5-thiadiazol-4-yl)pyridine oxalate. M.p. 136.degree.-138.degree. C., M.sup.+ : 315. Compound 102.

1,2,5,6-Tetrahydro-1-methyl-3-(3-(3-(2-pyrrolidon-1-yl) -1-propoxy)-1,2,5-thiadiazol-4-yl)pyridine oxalate. M.p. 160.degree.-161.degree. C., M.sup.+ : 322. Compound 103.

1,2,5,6-Tetrahydro-1-methyl-3-(3-(6-acetamido-1-hexyloxy)-1,2,5-thiadiazol-4-yl)pyridine oxalate. M.p. 114.degree.-116.degree. C., M.sup.+ : 338. Compound 104.

1,2,5,6-Tetrahydro-1-methyl-3-(3-(2-acetamido-1-ethoxy)-1,2,5-thiadiazol-4-yl)pyridine oxalate. M.p. 145.degree.-148.degree. C. M.sup.+ : 283. Compound 105.

1,2,5,6-Tetrahydro-1-methyl-3-(3-(2-(2-pyrrolidon-1-yl)-1-ethoxy)-1,2,5-thiadiazol-4-yl)pyridine oxalate. M.p. 170.degree.-171.degree. C., M.sup.+ : 309. Compound 106.

1,2,5,6-Tetrahydro-1-methyl-3-(3-(2-propionamido-1-ethoxy)-1,2,5-thiadiazol-4-yl)pyridine oxalate. M.p. 142.degree.-143.degree. C., M.sup.+ : 296. Compound 107.

1,2,5,6-Tetrahydro-1-methyl-3-(3-(2-(2-oxazolidon-3yl)-1-ethoxy)-1,2,5-thiadiazol-4-yl)pyridine oxalate. M.p. 157.degree.-159.degree. C., M.sup.+ : 310. Compound 108.

1,2,5,6-Tetrahydro-1-methyl-3-(3-(2-benzylthio-1-ethoxy)-1,2,5-thiadiazol-4-yl)pyridine oxalate. M.p. 133.degree.-134.degree. C., M.sup.+ : 347. Compound 109.

1,2,5,6-Tetrahydro-1-methyl-3-(3-(3-(1-pyrrolidyl)-1-propoxy)-1,2,5-thiadiazol-4-yl)pyridine oxalate. M.p. 141.degree.-142.degree. C., M.sup.+ : 308. Compound 110.

1,2,5,6-Tetrahydro-1-methyl-3-(3-(2-ureido-1-ethoxy)-1,2,5-thiadiazol-4-yl)pyridine oxalate. M.p. 200.degree. C. (decompose), M.sup.+ : 265. Compound 111.

3-(3-(2,4-Dimethylphenylpropoxy)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate from 3-(3-chloro-1,2,5-thiadiazol-4-yl)pyridine and 1-(2,4-dimethylphenyl)-3-propanol. M.p. 159.degree.-162.degree. C. Compound 161.

3-(3-(3,4-Dimethylphenylpropoxy)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate from 3-(3-chloro-1,2,5thiadiazol-4-yl)pyridine and 1-(3,4-dimethylphenyl)-3-propanol. M.p. 119.degree.-121.degree. C. Compound 162.

3-(3-(5-Ethyl-2-thienylmethoxy)-1,2,5thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate from 3-(3-chloro-1,2,5-thiadiazol-4yl)pyridine and 1-hydroxymethyl-5-ethylthiophene. M.p. 146.degree.-148.degree. C. Compound 163.

3-(3-(Pyrrolidin-1-yl)propoxy-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine dioxalate from 3-(3-chloro-1,2,5-thiadiazol-4-yl)pyridine and 1-pyrrolidin-1-yl-3-propanol. M.p. 141.degree. C. decomp. Compound 164.

3-(3-(4-Fluorophenylpropoxy)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate from 3-(3-chloro-1,2,5-thiadiazol-4-yl)pyridine and 1-(4-fluorophenyl)-3-propanol. M.p. 143.degree.-146.degree. C. Compound 165.

3-(3-(4-Chlorophenylpropoxy)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate from 3-(3-chloro-1,2,5-thiadiazol-4-yl)pyridine and 1-(4-chlorophenyl)-3-propanol. M.p. 154.degree.-155.degree. C. Compound 166.

3-(3-(3-Methylphenylpropoxy)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate from 3-(3-chloro-1,2,5-thiadiazol-4-yl)pyridine and 1-(3-methylphenyl)-3-propanol. M.p 138.degree.-139.degree.. Compound 167.

3-(3-(2,3-Dihydro-1-indenyloxy)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate from 3-(3-chloro-1,2,5-thiadiazol-4-yl)pyridine and 1-hydroxy-2,3-dihydroindene. M.p. 157.degree.-159.degree. C. Compound 168.

3-(3-(4-Methylphenylpropoxy)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate from 3-(3-chloro-1,2,5-thiadiazol-4-yl)pyridine and 1-(4-methylphenyl)-3-propanol. M.p. 155.degree.-159.degree. C. Compound 169.

3-(3-(1,2,3,4-Tetrahydro-2-naphtalyloxy)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate from 3-(3-chloro-1,2,5-thiadiazol-4-yl)pyridine and 1,2,3,4-tetrahydro-2-naphthol. M.p. 100.degree.-103.degree.. Compound 170.

3-(3-Phenylbutoxy-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate from 3-(3-chloro-1,2,5-thiadiazol-4-yl)pyridine and-1-phenyl-4-butanol. M.p. 128.degree.-130.degree. C. Compound 171.

3-(3-(2-Methylphenylpropoxy)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate from 3-(3-chloro-1,2,5-thiadiazol-4-yl)pyridine and 1-(2-methylphenyl)-3-propanol. M.p. 145.degree.-148.degree.. Compound 172.

3-(3-(2,5-Dimethylphenylpropoxy)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate from 3-(3-chloro-1,2,5-thiadiazol-4-yl)pyridine and 1-(2,5-dimethylphenyl)-3-propanol. M.p. 130.degree.-134.degree. C. Compound 173.

3-(3-Methylthioethoxy-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate from 3-(3-chloro-1,2,5-thiadiazol-4-yl)pyridine and methylthioethanol. M.p. 146.degree.-147.degree. C. Compound 174.

3-(3-Dimethylaminoethoxy-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine dioxalate from 3-(3-chloro-1,2,5-thiadiazol-4-yl)pyridine and dimethylaminoethanol. M.p. 148.degree.-150.degree. C. Compound 175.

3-(3-(3,4-Dichlorophenylpropoxy)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate from 3-(3-chloro-1,2,5-thiadiazol-4-yl)pyridine and 1-(3,4-dichlorophenyl)-3propanol. M.p. 149.degree.-151.degree. C. Compound 176.

3-(3-Dimethylaminopropoxy-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methyl-pyridine dioxalate from 3-(3-chloro-1,2,5-thiadiazol-4-yl)pyridine and 1-dimethylamino-3-propanol. M.p. 144.degree.-146.degree. C. Compound 177.

3-(3-(4-Ethylbenzyloxy)-1,2,5-thiadiazol-4yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate from 3-(3-chloro-1,2,5-thiadiazol-4l)pyridine and 1 -ethyl-4-hydroxymethylbenzene. M.p. 187.degree.-190.degree. C. Compound 178.

3-(3-(4-Methylphenylpropoxy)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate from 3-(3-chloro-1,2,5-thiadiazol-4-yl)pyridine and 1-(4-methylphenyl)-3-propanol. M.p. 147.degree.-149.degree. C. Compound 179.

3-(3-(4-Butylbenzyloxy)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate from 3-(3-chloro-1,2,5-thiadiazol-4-yl)pyridine and 1-butyl-4-hydroxymethylbenzene. M.p. 187.degree.-190.degree. C. Compound 180.

3-(3-(1-Ethylpentyloxy)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine fumarate from 3-(3-chloro-1,2,5-thiadiazol-4-yl)pyridine and 3-octanol. M.p. 117.degree.-120.degree. C. Compound 181.

3-(3-(1 -Ethylbutoxy)-1,2,5-thiadiazol-4-yt)-1,2,5,6-tetrahydro-1-methylpyridine fumarate from 3-(3-chloro-1,2,5-thiadiazol-4-yl)pyridine and 3-heptanol. M.p. 139.degree.-140.degree. C. Compound 182.

3-(3-(1-Methylpentyloxy)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine fumarate from 3-(3-chloro-1,2,5-thiadiazol-4-yl)pyridine and 2-hexanol. M.p. 143.degree.-144.degree. C. Compound 183.

3-(3-(5-Hexynyloxy)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate from 3-(3-chloro-1,2,5-thiadiazol-4-yl)pyridine and 6-hydroxy-1-hexyne. M.p. 120.degree.-122.degree. C. Compound 184.

3-(3-(4-Cyclohexylbutoxy)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate from 3-(3-chloro-1,2,5-thiadiazol-4-yl)pyridine and 1-cyclohexyl-4-butanol. M.p. 145.degree.-147.degree. C. Compound 185.

3-(3-(5-Hydroxyhexyloxy)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate from 3-(3-chloro-1,2,5-thiadiazol-4-yl)pyridine and 1,5-dihydroxyhexane. M.p. 128.degree.-129.degree. C. Compound 186.

3-(3-(5-Oxyhexyloxy)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate from 3-(3-chloro-1,2,5-thiadiazol-4-yl)pyridine and 5-oxo-1-hexanol. M.p. 143.degree.-144.degree. C. Compound 187.

3-(3-(3-Methyl-4-pentenyloxy)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate from 3-(3-chloro-1,2,5-thiadiazol-4-yl)pyridine and 1-hydroxy-3-methyl4-penten. M.p. 150.degree.-151.degree. C. Compound 188.

3-(3-(4-Methylenecyclohexylmethylloxy)-1,2,5-thiadiazol-4yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate from 3-(3-chloro-1,2,5-thiadiazol-4-yl)pyridine and 1-hydroxymethyl-4-methylenecyclohexan. M.p. 160.degree.-161.degree. C. Compound 189.

3-(3-(2,3-Dimethylpentyloxy)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate from 3-(3-chloro-1,2,5-thiadiazol-4-yl)pyridine and 1-hydroxy-2,3-dimethylpentan. M.p. 160.degree.-161.degree. C. Compound 190.

3-(3-(3-Cyclohexenylmethoxy)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate from 3-(3-chloro-1,2,5-thiadiazol-4-yl)pyridine and 1-hydroxymethyl-3-cyclohexen. M.p. 138.degree.-140.degree. C. Compound 191.

3-(3-Isobutylthioethoxy-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate from 3-(3-chloro-1,2,5-thiadiazol-4-yl)pyridine and isobutylthioethanol. M.p. 138.degree.-140.degree. C. Compound 192.

3-(3-Cyclopropylpropoxy-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate from 3-(3-chloro-1,2,5-thiadiazol-4-yl)pyridine and 1-cyclo-propyl-3-propanol. M.p. 151.degree.-153.degree. C. Compound 193.

3-(3-(2-Methylcyclopropylmethoxy)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate from 3-(3-chloro-1,2,5-thiadiazol-4-yl)pyridine and 1-hydroxymethyl-2-methylcyclopropan. Mp 121.degree.-122.degree. C. Compound 194.

3-(3-Cyclopentylpropyloxy-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate from 3-(3-chloro-1,2,5-thiadiazol-4-yl)pyridine and 1-cyclopentyl-3-propanol. M.p. 154.degree.-156.degree. C. Compound 195.

3-(3-(4Methylhexyloxy)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate from 3-(3-chloro-1,2,5-thiadiazol-4-yl)pyridine and 4-methyl-1-hexanol. M.p. 136.degree.-139.degree. C. Compound 196.

3-(3-(1-Methylhexyloxy)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate from 3-(3-chloro-1,2,5-thiadiazol-4-yl)pyridine and 2-heptanol. M.p. 118.degree.-119.degree. C. Compound 197.

3-(3-(4,4,4-Trifluorobutoxy)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate from 3-(3-chloro-1,2,5-thiadiazol-4-yl)pyridine and 4,4,4-trifluoro-1-butanol. M.p. 157.degree.-160.degree. C. Compound 198.

3-(3-(3-Methylpentyloxy)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine fumarate from 3-(3-chloro-1,2,5-thiadiazol-4-yl)pyridine and 3-methyl-1-pentanol. M.p. 133.degree.-134.degree. C. Compound 199.

3-(3-(6,6,6-Trifluorohexyloxy)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate from 3-(3-chloro-1,2,5-thiadiazol-4-yl)pyridine and 6,6,6-trifluoro-1-hexanol. M.p. 144.degree.-146.degree. C. Compound 200.

3-(3-(3-Cyclobutylpropoxy)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methyl-pyridine oxalate from 3-(3-chloro-1,2,5-thiadiazol-4-yl)pyridine and 3-cyclobutyl-1-propanol. M.p. 146.degree.-148.degree. C. Compound 201.

3-(3-lsopropoxyethoxy-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate from 3-(3-chloro-1,2,5-thiadiazol-4-yl)pyridine and isopropoxyethanol. M.p. 142.degree.-143.degree. C. Compound 202.

3-(3-Isoheptyloxy-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate from 3-(3-chloro-1,2,5-thiadiazol-4-yl)pyridine and isoheptanol. M.p. 150.degree.-152.degree. C. Compound 203.

3-(3-Isohexyloxy-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine maleate from 3-(3-chloro-1,2,5-thiadiazol-4-yl)pyridine and isohexanol. M.p. 72.degree.-74.degree. C. Compound 204.

3-(3-(2,2,2-Trifluoroethoxy)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine fumarate from 3-(3-chloro-1,2,5-thiadiazol-4-yl)pyridine and 2,2,2-trifluoroethanol. M.p. 131.degree.-133.degree. C. Compound 205.

3-(3-(2-Chlorophenylpropoxy-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate from 3-(3-chloro-1,2,5-thiadiazol-4-yl)pyridine and 1-(2-chlorophenyl)-3-propanol. M.p. 147.degree.-149.degree. C. Compound 206.

3-(3-(3-Cyclohexylpropoxy)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine fumarate from 3-(3-chloro-1,2,5-thiadiazol-4-yl)pyridine and 1-cyclopropyl-3-propanol. M.p. 89.degree.-90.degree. C. Compound 207.

3-(3-(2-Cyclohexyiethoxy)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate from 3-(3-chloro-1,2,5-thiadiazol-4-yl)pyridine and 2-cyclopropylethanol. M.p. 134.degree.-135.degree. C. Compound 208.

1,2,5,6-Tetrahydro-1-methyl-3-(3(2-ethylsulfinyl-1-ethoxy)-1,2,5-thiadiazol-4-yl)pyridine oxalate

1,2,5,6-tetrahydro-1-methyl-3-(3-(2-ethylsulfinyl-1-ethoxy)-1,2,5-thiadiazol-4-yl)pyridine oxalate was prepared in the same manner using 2-(ethylthio)-ethanol as the starting alcohol. The intermediate 3-(4-(2-ethylthio-1-ethoxy)-1,2,5-thiadiazol-3-yl)pyridine was oxidized with 1.1 equivalent of NalO.sub.4 and 1 equivalent MeSO.sub.3 H using water as the reaction solvent. After a reaction time of 3.5 h. the solution was made basic with 2N NaOH and extracted with ethyl acetate. The combined extracts were dried over MgSO.sub.4 and evaporated under vacuum. The resulting sulfoxide was then converted to the title compound in the same manner described above. M.p. 171.degree.-172.degree. C., M.sup.+ : 302. Compound 112.

1,2,5,6-Tetrahydro-3-(3-(5-oxohexyl)-1,2,5-thiadiazol-4-yl)-1-methylpyridin

1,2,5,6-tetrahydro-3-(3-(5-hydroxyhexyl)-1,2,5-thiadiazol-4-yl)-1-methylpyridine was prepared in the same manner using 1,5-hexandiol. Oxidation of this compound to the named ketone was carried out under conditions as follows. To a -70.degree. C. solution of oxalylchloride (420 .mu.l, 4.8 mmol) in 25 ml CH.sub.2 Cl.sub.2 was added DMSO (750 .mu.l, 10.6 mmol) at a rate so as to maintain the reaction temperature below -45.degree. C. Two min. after the addition 1,2,5,6-tetrahydro-3-(3-(5-hydroxyhexyl)-1,2,5-thiadiazol-4-yl)-1-methylpyridine (1.3 g, 4.4 mmol) in 20 ml CH.sub.2 Cl.sub.2 was added slowly, keeping the temperature below -45.degree. C. After 15 min. Et.sub.3 N (3 ml, 21.8 mmol) was added and the reaction was warmed to room temperature. Brine (50 ml) was added and the mixture was extracted three times with 50 ml CH.sub.2 Cl.sub.2. The combined extracts were dried over Na.sub.2 SO.sub.4 and evaporated under vacuum. The resulting oil was chromatographed on silica gel (90% CHCl.sub.3, 2% MeOH as eluent), affording 810 mg of an oil, which was dissolved in MeOH and treated with oxalic acid (250 mg, 2.8 mmol). The resulting oxalate salt was recrystallized from MeOH/EtOAc, affording 860 mg. M.p. 143.degree.-1440.degree. C., M.sup.+ : 295. Compound 113.

EXAMPLE 67

A. 3-(3-Chloro-1,2,5-oxadiazol-4-yl)pyridine

To a solution of 3-(3-amino-1,2,5-oxadiazol-4-yl)pyridine (1.0 g, 6.2 mmol) in glacial acetic acid (16 ml) and concentrated hydrochloric acid (5.2 ml) was added CuCl.sub.2 (938 mg, 7 mmol) and copper coils (100 mg) at 0.degree. C. After 10 min. a solution of sodium nitrite (483 mg, 7 mmol) in water (3 ml) was added dropwise at 5.degree. C. The reaction mixture was stirred additionally 30 min. at 0.degree. C. Aqueous sodium hydroxide (2N) was added to alkaline pH and the mixture extracted with ether. The ether phases were dried and evaporated to give a mixture of the title compounds. Separation by column chromatography (SiO.sub.2, eluent: ethyl acetate) gave the chloro compound, upper spot, in 230 mg yield.

B. 3-(3-(3-Phenylpropylthio)-1,2,5-oxadiazol-4-yl)pyridine

Sodium hydrogen sulfide monohydrate (0.74 g, 10.5 mmol) was added to a solution of 3-(3-chloro-1,2,5-oxadiazol-4-yl)pyridine (1.27, 7.0 mmol) in DMF (30 ml) at room temperature and the reaction mixture was stirred for 1 h. Potassium carbonate (2.0 g, 14.5 mmol) and 1-bromo-3-phenylpropane (2.4 g, 12 mmol) were added and the reaction mixture was stirred for additionally 24 h. Water (50 ml) was added and extracted with ether. The combined ether phases were dried and evaporated. Purification by column chromatography (SiO.sub.2, eluent: ethyl acetate/methylene chloride (1:1)) gave the title compound.

C. 3-(3-(3-Phenylpropylthio)-1,2,5-oxadiazol-4-yl)-1-methylpyridinium iodide

Methyl iodide (1 ml, 15 mmol) was added to a solution of 3-(3-(3-phenylpropylthio)-1,2,5-oxadiazol-4-yl)pyridine (7 mmol) in acetone and the reaction mixture was stirred at room temperature for 20 h. and evaporated.

D. 3-(3-(3-Phenylpropylthio)-1,2,5-oxadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate

Sodium borohydride (650 mg, 17 mmol) was added to a solution of 3-(3-(3-phenylpropylthio)-1,2,5-oxadiazol-4yl)-1-methylpyridinum iodide (7 mmol), in ethanol (99.9%, 20 ml) and the reaction mixture was stirred at -10.degree. C. for 1 h. After evaporation the residue was dissolved in water and extracted with ethyl acetate. The dried organic phases were evaporated and the residue purified by column chromatography (SiO.sub.2, eluent: ethyl acetate/methanol (4:1)). The title compound was crystallized as the oxalate salt from acetone and recrystallized to yield 170 mg. M.p. 106.degree.-108.degree. C. Compound 114.

The following compound was made in exactly the same manner using the appropriate alkylhalogenide:

3-(3-(2-Phenoxyethylthio)-1,2,5-oxadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate. M.p. 122.degree.-124.degree. C. Compound 115.

3-(3-Pentylthio-1,2,5-oxadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate from 3-(3-chloro-1,2,5-oxadiazol-4-yl)pyridine, sodium hydrogensulfide and 1-bromopentane. M.p. 123.degree.-124.degree. C. Compound 212.

3-(3-Hexylthio-1,2,5-oxadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate from 3-(3-chloro-1,2,5-oxadiazol-4-yl)pyridine, sodium hydrogen-sulfide and 1-bromohexane. M.p. 111.degree.-113.degree. C. Compound 213.

3-(3-(4-Pentynylthio)-1,2,5-oxadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate from 3-(3-chloro-1,2,5-oxadiazol-4-yl)pyridine, sodium hydrogen-sulfide and 1-bromo-4-pentyne. M.p. 119.degree.-120.degree. C. Compound 214.

EXAMPLE 68

1-(3-(3-Pyridyl)-1,2,5-thiadiazol-4-ylthio)-4-(3-(1-methyl-1,2,5,6-tetrahydropyridin-3-yl)-1,2,5-thiadiazol-4-ylthio)butane oxalate

To a solution of 3-(3-chloro-1,2,5-thiadiazol-4-yl)-1-methyl-1,2,5,6-tetrahydropyridine (0.43 g, 2 mmol) in DMF (30 ml) was added sodiumhydrogensulfide (0.3 g, 4 mmol). The reaction mixture was stirred at room temperature for 1 h. Potassium carbonate (1 9) and 3-(3-(4-chlorobutylthio)-1,2,5-thiadiazol-4-yl)-pyridine were added and the reaction mixture stirred at room temperature overnight. Water (200 ml) was added and the water phase extracted with ether (3.times.100 ml). The ether extracts were dried over magnesium sulfate and evaporated. The residue was purified by column chromatography (eluent: ethyl acetate/methanol 9:1). The free base obtained was crystallized with oxalic acid from acetone in 0.9 g yield. (Compound 116). M.p. 127.degree.-129.degree. C.

EXAMPLE 69

1-(1-Methyltetrazol-5-ylthio)-4-(3-(1-methyl-1,2,5,6-tetrahydropyridin-3-yl)-1,2,5-thiadiazol-4-ylthio)butane oxalate

To a solution of 3-(3-(4-chlorobutylthio)-1,2,5-thiadiazol-4-yl)-1-methyl-1,2,5,6-tetrahydropyridine (0.30 g, 1 mmol) in DMF (30 ml) were added 1-methyl-5-mercaptotetrazol (0.35 g, 3 mmol) and potassium carbonate (2 g). The reaction mixture was stirred at room temperature for 60 h. 1N hydrochloric acid was added (200 ml) and the water phase was extracted with ether (2.times.100 ml). The water phase was basified with solid potassium carbonate and extracted with ether (3.times.100 ml). The ether extracts from the alkaline extractions were combined and dried over magnesium sulfate. The ether phase was evaporated and the residue was crystallized with oxalic acid from acetone giving the title compound in 0.4 g yield. (Compound 117). M.p. 77.degree.-79.degree. C.

EXAMPLE 70

The following compounds were made in exactly the same manner as described in example 69 by using the reagents indicated.

1-(2-Methyl-1,3,4-thiadiazol-5-ylthio)-4-(3-(1-methyl-1,2,5,6-tetrahydropyridin-3-yl)-1,2,5-thiadiazol-4-ylthio)butane oxalate from 3-(3-(4-chlorobutylthio)-1,2,5-thiadiazol-4-yl)-1-methyl-1,2,5,6-tetrahydropyridine and 2-methyl-5-mercapto-1,3,4-thiadiazole. (Compound 118). M.p. 102.degree.-104.degree. C.

1-(2-Thiazolin-2-ylthio)-4-(3-(1-methyl-1,2,5,6-tetrahydropyridin-3-yl)-1,2,5-thiadiazol-4-ylthio)butane oxalate from 3-(3-(4-chlorobutylthio)-1,2,5-thiadiazol-4-yl)-1-methyl-1,2,5,6-tetrahydropyridine and 2-thiazoline-2-thiol. (Compound 119). M.p. 116.degree.-117.degree. C.

1-(2-Benzoxazolylthio)-4-(3-(1-methyl-1,2,5,6-tetrahydropyridin-3-yl)-1,2,5-thiadiazol-4-ylthio)butane oxalate from 3-(3-(4-chlorobutylthio)-1,2,5-thiadiazol-4-yl)-1-methyl-1,2,5,6-tetrahydropyridine and 2-mercaptobenzoxazole. (Compound 120). M.p. 156.degree.-158.degree. C.

1 -(2-Methyl-1,3,4-thiadiazol-5-ylthio)-5-(3-(1-methyl-1,2,5,6-tetrahydropyridin-3-yl)-1,2,5-thiadiazol-4-ylthio)pentane oxalate from 3-(3-(5-chloropentylthio)-1,2,5-thiadiazol-4-yl)-1-methyl-1,2,5,6-tetrahydropyridine and 2-methyl-5-mercapto-1,3,4-thiadiazole. (Compound 121). M.p. 69.degree.-70.degree. C.

1-(2-Benzthiazolylthio)-5-(3-(1-methyl-1,2,5,6-tetrahydropyridin-3-yl)-1,2,5-thiadiazol-4-ylthio)pentane oxalate from 3-(3-(5-chloropentylthio)-1,2,5-thiadiazol-4-yl)-1-methyl-1,2,5,6-tetrahydropyridine and 2-mercaptobenzthiazole. (Compound 122). M.p. 116.degree.-117.degree. C.

1-(1-Methyltetrazol-5-ylthio)-5-(3-(1-methyl-1,2,5,6-tetrahydropyridin-3-yl)-1,2,5-thiadiazol-4-ylthio)pentane oxalate from 3-(3-(5-chloropentylthio)-1,2,5-thiadiazol-4-yl)-1-methyl-1,2,5,6-tetrahydropyridine and 1-methyl-5-mercapto-tetrazole. (Compound 123). M.p. 96.degree.-97.degree. C.

1-(2-Methyl-1,3,4-thiadiazol-5-ylthio)-6-(3-(1-methyl-1,2,5,6-tetrahydropyridin-3-yl)-1,2,5-thiadiazol-4-ylthio)hexane oxalate from 3-(3-(6-chlorohexylthio)-1,2,5thiadiazol-4-ylthio)hexane oxalate from 3-(3-(6-chlorohexylthio)-1,2,5-thiadiazol-4-yl)-1-methyl-1,2,5,6-tetrahydropyridine and 2-methyl-5-mercapto-1,3,4-thiadiazole. (Compound 124). M.p. 85.degree.-86.degree. C.

1-(1-Methyltetrazol-5-ylthio)-6-(3-(1-methyl-1,2,5,6-tetrahydropyridin-3-yl)-1,2,5-thiadiazol-4-ylthio) hexane oxalate from 3-(3-(6-chlorohexylthio)-1,2,5-thiadiazol-4-yl)-1-methyl-1,2,5,6-tetrahydropyridine and 1-methyl-5-mercaptotetrazole. (Compound 125). M.p. 65.degree.-66.degree. C.

1-(2-Thiazolin-2-ylthio)-6-(3-(1-methyl-1,2,5,6-tetrahydropyridin-3-yl)-1,2,5-thiadiazol-4-ylthio)hexane oxalate from 3-(3-(6-chlorohexylthio)-1,2,5-thiadiazol-4-yl)-1-methyl-1,2,5,6-tetrahydropyridine and 2-thiazoline-2-thiol. (Compound 126). M.p. 61.degree.-62.degree. C.

EXAMPLE 71

3-(3-Methylsulfonyl-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate hemiacetone

A solution of 3-(3-methylthio-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate (0.25 g, 0.0079 mol) in H.sub.2 O (10 ml) was cooled in an ice-water bath as a solution of oxone (0.7 g, 0.00114 mol) in H.sub.2 O (5 ml) was added dropwise. Cooling was removed and after 5 h excess NaHSO.sub.3 was added. The solution was cooled in an ice-water bath, the solution made basic, and the mixture extracted with CH.sub.2 Cl.sub.2 (3.times.25 ml). The extracts were dried, the solvent evaporated, and the residue purified by radial chromatography (5% EtOH--0.5% NH.sub.4 OH--CHCl.sub.3) to give a white crystalline solid (0.2 g). The oxalate salt recrystallized from acetone to give colorless crystals. M.p. 96.degree.-97.5.degree. C. (Compound 127). Analysis and NMR confirmed that the salt contained 0.5 mol of acetone. Analysis C.sub.9 H.sub.13,N.sub.3 O.sub.2 S--C.sub.2 H.sub.2 O.sub.4 -0.5C.sub.3 H.sub.6 O,C,H,N; Theory C, 39.68; H, 4.79; N, 11.10; Found C, 39.52; H, 4.85; N, 11.19.

3-(3-�2-(1 -Pyrrolidinyl)ethoxyl!-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine dioxalate

A suspension of NaH (0.0075 mol) in THF (25 ml) was treated with 2-hydroxyethylpyrrolidine (1 ml, 0.0086 mol) and after 30 min. the free base of (Compound 127) (0.6 g, 0.0023 mol), was added. After another hour, H.sub.2 O (2 ml) was added and the solvent evaporated. The residue was suspended in H.sub.2 O and extracted with CH.sub.2 Cl.sub.2 (3.times.25 ml). The extracts were dried, the solvent evaporated, and the residue purified by radial chromatography (20% EtOH--2% NH.sub.4 OH--CHCl.sub.3) to give a straw colored liquid (0.4 g). The dioxalate salt recrystallized from EtOH to give a white solid. M.p. 186.degree.-188.degree. C. (Compound 128). Analysis C.sub.14 H.sub.22,N.sub.4 OS--2C.sub.2 H.sub.2 O.sub.4,C,H,N; Theory C, 45.57; H, 5.52; N, 11.81; Found C, 45.53; H, 5.50; N, 11.61.

EXAMPLE 72

3-(3-(3-(5-Methyl-2-thienyl)-1-propoxy)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate

Sodium hydride (10.2 mmol) was added to a solution of 3-(5-methyl-2-thienyl)-1-propanol (4.0 g, 25.5 mmol) in THF (40 ml). The mixture was stirred for 1 h at room temperature, whereupon a solution of 3-(3-chloro-1,2,5-thiadiazol-4-yl)pyridine (1.0 g, 5.1 mmol) in THF (10 ml) was added dropwise to the reaction mixture. After stirring overnight at room temperature, the reaction was quenched with water then extracted with diethyl ether. The organic phase was dried over NaCl/Na.sub.2 SO.sub.4 then evaporated to yield crude 3-(3-(5-methyl-2-thienyl)propoxy-1,2,5-thiadiazol-4-yl)pyridine. A solution of 3-(3-(5-methyl-2-thienyl)propoxy-1,2,5-thiadiazol-4-yl)pyridine (1.0 g, 3.2 mmol) and iodomethane (2.3 g, 16.0 mmol) in 60 ml of acetone was refluxed overnight. The solution was evaporated to yield 1.5 g of the quaternized product. Sodium borohydride (0.6 g, 16.0 mmol) was carefully added to a solution of the quaternized product (1.5 g) in ethanol (30 ml). The reaction was evaporated and the resulting residue was taken up in water and extracted with methylene chloride (3.times.100 ml). The organic phase was dried over NaCl/Na.sub.2 SO.sub.4 then evaporated. The residue was purified by radial chromatography eluting with 0.5% NH.sub.4 OH/5.0% EtOH in CHCl.sub.3. The oxalate salt was made to yield 337 mg of the title compound. M.p. 134.degree.-137.degree. C. (Compound 129).

The following compounds were made in the same manner as described above using the indicated alcohol instead of 3-(5-methyl-2-thienyl)-1-propanol:

3-(3-((5-Propyl-2-thienyl)methoxy)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate (Compound 130) from (5-propyl-2-thienyl)-methanol. M.p. 134.degree.-135.degree. C.

3-(3-(3-(5-Pentyl-2-thienyl)-1-propoxy)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate (Compound 131) from 3-(5-pentyl-2-thienyl)-1-propanol. M.p. 138.degree.-140.degree. C.

3-(3-(3-(2-Thienylthio)-1-propoxy)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate (Compound 132) from 3-(2-thienylthio)-1-propanol. M.p. 102.degree.-110.degree. C.

EXAMPLE 73

3-(3-(3-(2-Thienyl)-1-propylthio)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate

A solution of 3-(3-chloro-1,2,5-thiadiazol-4-yl)pyridine (2.0 g, 10.1 mmol) in DMF (10 ml) was cooled to 5.degree. C. whereupon potassium carbonate (2.8 g, 20.2 mmol) and sodium hydrosulfide monohydrate (1.5 g, 20.2 mmol) were added to the reaction. Stirred for 1 h then potassium carbonate (1.4 g, 10.1 mmol) and a solution of 3-(2-thienyl)-1-chloro-propane (1.8 g, 11.2 mmol) in DMF (5 ml) were added to the reaction and stirred for 1 h at room temperature. The reaction was quenched with water then extracted with methylene chloride (3.times.75 ml). The organic phase was dried over NaCl/Na.sub.2 SO.sub.4 then evaporated. The residue was purified by flash chromatography eluting with 1:1 ethyl acetate/hexanes to yield 1.0 g of 3-(3-(3-(2-thienyl)-1-propylthio)-1,2,5-thiadiazol-4-yl)pyridine. Quaternization and reduction was done as described in example 72. (Compound 133). M.p. 98.degree.-100.degree. C.

The following compounds were made in exactly the same manner as described above using the indicated alkylhalogenide:

3-(3-(2-Thienylmethylthio) -1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate (Compound 134) using (2-thienyl)-chloromethane. M.p. 131.degree.-135.degree. C.

3-(3-(3-(2-Oxazolidinon-3-yl)-1-propylthio) -1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate (Compound 135) using 3-(2-oxazolidinon-3-yl)-1-chloropropane. M.p. 104.degree.-109.degree. C.

3-(3-(3-(2-Thiazolidinon-3-yl)-1-propylthio-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate (Compound 136) using 3-(2-thiazolidinon-3-yl)-1-chloropropane. M.p. 75.degree.-81.degree. C.

3-(3-(5-Pentyl-2-thienyl)methylthio-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate (Compound 137) using (5-pentyl-2-thienyl)chloromethane. M.p. 143.degree.-146.degree. C.

(R)-(+) 3-(3-(3-(4-Benzyl-2-oxazolidinon-3-yl)-1-propylthio)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate (Compound 138) using (R) 3-(4-benzyl-2-oxazolidinon-3-yl)-1-chloropropane. M.p. 124.degree.-133.degree. C.

(S)-(-) 3-(3-(3-(4-Benzyl-2-oxazolidinon-3-yl)-1-propylthio)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate (Compound 139) using (S)-3-(4-benzyl-2-oxazolidinon-3-yl)-1-chloropropane. M.p. 132.degree.-135.degree. C.

(4R,5S)-3-(3-(3-(4-Methyl-5-phenyl-2-oxazolidinon-3-yl)-1-propylthio)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate (Compound 140) using (4R,5S)-3-(4-methyl-5-phenyl-2-oxazolidinon-3-yl)-1-chloropropane. M.p. 102.degree.-106.degree. C.

(S)-3-(3-(3-(4-Isopropyl-2-oxazolidinon-3-yl)-1-propylthio)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate (Compound 141) using (S)-3-(4-isopropyl-2-oxazolidinon-3-yl)-1-chloropropane. M.p. 75.degree.-79.degree. C.

(S)-3-(3-(3-(4-Ethyl-2-oxazolidinon-3-yl)-1-propylthio)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate (Compound 142) using (S)-3-(4-ethyl-2-oxazolidinon-3-yl)-1-chloropropane. M.p. 69.degree.-71.degree. C.

(S)-3-(3-(3-(4-(2-Butyl)-2-oxazolidinon-3-yl)-1-propylthio-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate (Compound 143) using (S)-3-(4-(2-butyl)-2-oxazolidinon-3-yl)-1-chloropropane. M.p. 77.degree.-80.degree. C.

3-(3-(3-(4-Propyl-2-oxazolidinon-3-yl)-1-propylthio)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate (Compound 144) using 3-(4-propyl-2-oxazolidinon-3-yl)-1-chloropropane. M.p. 65.degree.-68.degree. C.

EXAMPLE 74

A. 4-Methyl-1-(phenoxycarbonyl)-1,4-dihydropyridine

In a dry 500 ml three neck flask under nitrogen, a solution of cuprous iodide (0.28 g, 1.5 mmol) and dimethyl sulfide (8 ml) in 30 ml of dry THF was stirred at room temperature for 10 minutes. Pyridine (2.43 ml, 30 mmol) in 120 ml of dry THF was added to the reaction, then cooled to -25.degree. C. Phenylchloroformate (3.9 ml, 30 mmol) in 10 ml dry THF was added to the reaction via an addition funnel (a thick brown precipitate formed immediately upon addition). The mixture was stirred for 15 minutes. Methyl magnesium chloride (10 ml, 30 mmol) was added to the mixture via syringe whereupon the brown precipitate dissolved. The reaction was stirred at -25.degree. C. for 20 minutes then stirred at room temperature for 20 minutes. 20% NH.sub.4 Cl.sub.(aq) (70 ml) was added to the reaction. The mixture was then extracted with 150 ml diethyl ether. The organic extract was then washed with 40 ml portions of 20% NH.sub.4 Cl.sub.(aq) /NH.sub.4 OH (1:1), water, 10% HCl.sub.(aq), water, and brine. The organic layer was then dried over NaCl/Na.sub.2 SO.sub.4, filtered, and concentrated to yield 5.9 g of a yellow oil. Kugelrohr distillation (bp. 150.degree.-170.degree. C., 1 mmHg) to yield 4.9 g (77%) of the desired compound (A).

B. 3-Formyl-4-methyl-1-(phenoxycarbonyl)-1,4-dihydropyridine

To a dry 50 ml flask under nitrogen, DMF (7.44 ml, 97 mmol) in 10 ml of dichloromethane was cooled to 0.degree. C. Phosphorus oxychloride (4.5 ml, 48 mmol) was slowly added to the solution. The solution was stirred at room temperature for 30 minutes. (A) (4.7 g, 22 mmol) in 40 ml of dichloromethane was stirred in a 100 ml two neck flask under nitrogen at 0.degree. C. The DMF/Phosphorus oxychloride solution was transferred to an addition funnel via cannula then slowly added to the (A)/dichloromethane solution. The ice bath was then removed, and the reaction was stirred at room temperature for 20 hours. The reaction was cooled to 0.degree. C. whereupon a solution of potassium acetate (15 g) in 50 ml of water was carefully added via the addition funnel. The mixture was then allowed to reflux for 20 minutes. The methylene chloride layer was separated then extracted once more with 100 ml methylene chloride. The organic phases were combined then washed with 40 ml portions of water, K.sub.2 CO.sub.3(aq), water and brine, then dried over NaCl/Na.sub.2 SO.sub.4. The organics were concentrated on a rotary evaporator to yield 4 g of a brown oil. Purified by flash chromatography over silica gel eluting with ethyl acetate/hexane. Yield 2.0 g (37%) of the desired compound (B).

C. 4-Methyl-3-pyridinecarboxaldehyde

Methanol (85 ml), triethylamine (1.4 g), and (B) (5.0 g, 20.6 mmol) were placed in a 250 ml flask over nitrogen. The solution was refluxed for 3 hours. The reaction was then concentrated and 5% Pd/C (0.5 g) and toluene (85 ml) were added to the flask. This mixture was refluxed for 2 hours, then cooled to room temperature. The 5% Pd/C was removed by filtration and the filtrate was concentrated.

The resulting oil was purified by flash chromatography over silica gel eluting with ethyl acetate/hexane. The yield of (C) was 1.3 g (47%).

D. Alpha-amino-alpha(3-(4-methylpyridyl))acetonitrile

Dissolved potassium cyanide (7.3 g, 112.6 mmol) and ammonium chloride (6.0 g, 112.6 mmol) in water (150 ml) in a 250 ml flask under nitrogen. (C) (10.9 g, 90.1 mmol) was added to the reaction which was stirred at room temperature overnight. The reaction mixture was extracted with ethyl acetate (3.times.300 ml). The organic extracts were combined, dried over NaCl/Na.sub.2 SO.sub.4, then concentrated to yield 11 g of a brown oil (D). Used directly in the next step.

E. 3-(3-Chloro-1,2,5-thiadiazol-4-yl)-4-methylpyridine

Sulfurmonochloride (73.5 mmol, 5.9 ml) in DMF (90 ml) was placed in a 250 ml flask under nitrogen and cooled to -25.degree. C. (D) (3.6 g, 24.5 mmol) in DMF (10 ml) was added to the reaction via an addition funnel. The reaction was allowed to stir overnight. After warming to room temperature, water (30 ml) and diethyl ether (60 ml) were added to the reaction and the ether layer was separated, then discarded. The reaction was then basified with 50% NaOH.sub.(aq), then extracted with diethyl ether (4.times.90 ml). The organic extracts were co bined, dried over NaCl/Na.sub.2 SO.sub.4, and concentrated to yield a brown oil. The oil was purified by flash chromatography over 100 g silica gel, eluting with 0.05% NH.sub.4 OH/0.5% ethanol in chloroform. Yield of (E) was 2 g (38%).

F. 3-(3-Methoxy-1,2,5-thiadiazol-4-yl)-4-methylpyridine

A solution of sodium (0.32 g, 14 mmol) in methanol (10 ml) was prepared in a 25 ml flask under nitrogen. (E) (0.6 g, 2.8 mmol) was added to the reaction and was heated at 50.degree. C. for 3 hours, then stirred overnight at room temperature. Concentrated on the rotary evaporator then dissolved the resulting solid in 1N HCl.sub.(aq) and washed with diethyl ether. The aqueous layer was basified with 5N NaOH.sub.(aq), then extracted with methylene chloride (4.times.50 ml). The combined organic extracts were dried over NaCl/Na.sub.2 SO.sub.4 and concentrated to yield 344 mg of an oil (F) (60%).

G. 3-(3-Methoxy-1,2,5-thiadiazol-4-yl)-4-methylpyridinium iodide

A mixture of (F) (335 mg, 1.6 mmol), iodomethane (1.14 g, 8.0 mmol), and acetone (100 ml) was stirred in a 250 ml flask under nitrogen overnight at room temperature. Concentrated the reaction on the rotary evaporator to yield 500 mg of a yellow solid (G). Used directly in next step.

H. 1,2,5,6-Tetrahydro-3-(3-methoxy-1,2,5-thiadiazol-4-yl)-1,4-dimethylpyridine fumarate

Sodium borohydride (300 mg, 8.0 mmol) was added to a solution of (G) (1.6 mmol) and ethanol (15 ml) in a 50 ml flask under nitrogen. The reaction was allowed to stir overnight at room temperature. The reaction was concentrated on the rotary evaporator. Dissolved the resulting solid in 1N HCl.sub.(aq) (75 ml), then washing with diethyl ether. The aqueous layer was basified, then extracted with methylene chloride (4.times.75 ml). The combined organic extracts were dried over NaCl/Na.sub.2 SO.sub.4, and concentrated to yield an oil which was purified by flash chromatography (silica gel eluting with NH.sub.4 OH/ethanol in chloroform). Yield was 91 mg. Isolated as fumarate salt, 130.4 mg. M.p. 99.degree.-105.degree. C. Analysis calc. for C.sub.14 H.sub.19 N.sub.3 O.sub.5 S. C: 49.26; H: 5.61; N: 12.31. Found C: 49.11; H: 5.53; N: 12.03. Compound 145.

EXAMPLE 75

The following compound was made in exactly the same manner as described in example 74 F through H using hexanol instead of methanol:

3-(3-Hexyloxy-1,2,5-thiadiazol-4yl)-1,2,5,6-tetrahydro-1,4-dimethylpyridine oxalate. M.p. 109.degree.-111.degree. C. Analysis calc. for C.sub.17 H.sub.27 N.sub.3 O.sub.5 S. C: 52.97; H: 7.06; N: 10.70. Found C: 53.17; H: 6.88; N: 10.98. Compound 146.

EXAMPLE 76

A. Alpha-amino-alpha-(6-methyl-3-pyridinyl)acetonitrile

To a solution of potassium cyanide (6.96 g, 107 mmol) and ammonium chloride (5.72 g, 107 mmol) in water (5 ml) was added 6-methyl-3-pyridin-carboxaldehyde (8.68 g, 71.5 mmol) and the reaction mixture was stirred at room temperature for 18 h. The reaction mixture was basified with 50% NaOH and extracted with ethyl acetate. The organic phase was dried (MgSO.sub.4) and evaporated to give the crude desired product in 7 g yield. The product was used without further purification.

B. 3-(3-Chloro-1,2,5-thiadiazol-4-yl)-6-methylpyridine

A solution of sulphurmonochloride (11.7 ml, 142 mmol) in DMF (50 ml) was slowly added to a solution of alpha-amino-alpha-(6-methyl-3-pyridinyl)acetonitrile (7 g, 47 mmol) at room temperature. The reaction mixture was stirred for 18 h and thereafter basified with 50% NaOH and extracted with ether. The ether phases were dried (MgSO.sub.4) and evaporated. The residue was purified by column chromatography (eluent, EtOAc:CH.sub.2 Cl.sub.2 (1:1)) to give the wanted product in 5.30 g (54%) yield.

C. 3-(3-Hexylthio-1,2,5-thiadiazol-4-yl)-6-methylpyridine

Sodium hydrogen sulfide monohydrate (0.33 g, 4.4 mmol) was added to a solution of 3-(3-chloro-1,2,5-thiadiazol-4-yl)-6-methylpyridine (0.85 g, 4 mmol) in DMF (20 ml) at room temperature and the reaction mixture was stirred for 1 h. Potassium carbonate (1.65 g, 12 mmol) and 1-hexylbromide (0.99 g, 6 mmol) were added and the reaction mixture was stirred for additionally 24 h. 1N HCl was added and the reaction mixture was extracted once with ether. The aqueous phase was basified with 50% NaOH and extracted with ether. The ether phases were dried and evaporated to give crude title compound.

D. 3-(3-Hexylthio-1,2,5-thiadiazol-4-yl)-1,6-dimethylpyridinium iodide

Methyl iodide (1 ml, 15 mmol) was added to a solution of 3-(3-hexylthio-1,2,5-thiadiazol-4-yl)-6-methylpyridine (4 mmol) in acetone (5 ml) and the reaction mixture was stirred at room temperature for 20 h. Evaporation of the reaction mixture gave the crude product, which was used without further purification.

E. 3-(3-Hexylthio-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1,6-dimethylpyridine oxalate

Under nitrogen, sodium borohydride (380 mg, 10 mmol) was added to a solution of 3-(3-hexylthio-1,2,5-thiadiazol-4-yl)-1,6-dimethylpyridinium iodide (4 mmol) in ethanol (99.9%, 20 ml) at -10.degree. C. The reaction mixture was stirred at -10.degree. C. for 1 h. After evaporation the residue was dissolved in water and extracted with ethyl acetate. The dried organic phases were evaporated and the residue purified by column chromatography (eluent: EtOAc:MeOH (4:1)). The title compound was crystallized as the oxalate salt from acetone. Recrystallization from acetone gave the wanted product in 700 mg yield. M.p. 127.degree.-128.degree. C. (Compound 147).

EXAMPLE 77

The following compounds were made in the same manner as described in example 76C through E using the appropriate alkylbromide instead of 1-hexylbromide:

3-(3-Pentylthio-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1,6-dimethylpyridine oxalate. M.p. 112.degree.-113.degree. C. (Compound 148).

3-(3-(4-Cyanobenzylthio)-1,2,5thiadiazol-4-yl)-1,2,5,6-tetrahydro-1,6-dimethylpyridine oxalate. M.p. 74.degree.-76.degree. C. (Compound 149).

3-(3-(4-Cyanobutylthio)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1,6-dimethylpyridine oxalate. M.p. 99.degree.-101.degree. C. (Compound 150).

3-(3-Butylthio-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1,6-dimethylpyridine oxalate. M.p. 119.degree.-120.degree. C. (Compound 151).

3-(3-Ethylthio-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1,6-dimethylpyridine oxalate. M.p. 154.degree.-155.degree. C. (Compound 152).

3-(3-(4-Pentynylthio)-1,2,5-thiadiazol-4yl)-1,2,5,6-tetrahydro-1,6-dimethylpyridine oxalate. M.p. 111.degree.-113.degree. C. (Compound 153).

3(3-(3-Phenylpropylthio)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1,6-dimethylpyridine oxalate. M.p. 125.degree.-126.degree. C. (Compound 154).

EXAMPLE 78

A. 3-(3-Hexyloxy-1,2,5-thiadiazol-4-yl)-6-methylpyridine

Sodium hydride (0.72 g, 15 mmol) was dissolved in dry THF (20 ml) and 1-hexanol (1.53 g, 15 mmol) and a solution of 3-(3-chloro-1,2,5-thiadiazol-4-yl)-6-methylpyridine (1.06 g, 5 mmol) in dry THF (15 ml) was added. The reaction mixture was stirred for 2 h. After addition of water the mixture was extracted with ether, and the ether phase was dried and evaporated. The residue consisted of the crude title compound, which was used without further purification.

B. 3-(3-Hexyloxy-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1,6-dimethylpyridine oxalate

M.p. 99.degree.-100.degree. C. (Compound 155) was made in the same manner as described in example 76D through E.

EXAMPLE 79

The following compounds were prepared in the same manner as described in example 78 using the appropriate alcohol instead of 1-hexanol:

3-(3-Pentyloxy-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1,6-dimethylpyridine oxalate. M.p. 122.degree.-123.degree. C. (Compound 156).

3-(3-Butoxy-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1,6-dimethylpyridine oxalate. M.p. 133.degree.-134.degree. C. (Compound 157).

3-(3-(4-Pentenyloxy)-1,2,5-thiadiazol-4yl)-1,2,5,6-tetrahydro-1,6dimethylpyridine oxalate. M.p. 133.degree.-134.degree. C. (Compound 158).

3-(3-(3-Hexynyloxy)-1,2,5-thiadiazol-4yl)-1,2,5,6-tetrahydro-1,6-dimethylpyridine oxalate. M.p. 126.degree.-128.degree. C. (Compound 159).

3-(3-Ethoxy-1,2,5thiadiazol-4yl)-1,2,5,6-tetrahydro-1,6-dimethylpyridine oxalate. M.p. 128.degree.-129.degree. C. (Compound 160).

EXAMPLE 80

3-(3-(3-Carboxypropylthio)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine

A solution of 3-(3-(3-carboxypropylthio)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine hydrochloride (0.70 g, 2 mmol) in concentrated hydrochloric acid (10 ml) was heated at reflux for 6 hours. The reaction mixture was evaporated at reduced pressure. The residue was dissolved in water and neutralized with a sodiumhydroxide solution giving the title compound in 80% yield. M.p. 99.degree.-101.degree. C. Compound 258.

In exactly the same manner the following compounds were prepared:

3-(3-(3-Carboxypropoxy)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine. M.p. 113.degree.-116.degree. C. Compound 259.

3-(3-(5-Carboxypentylthio)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine. M.p. 110.degree.-112.degree. C. Compound 260.

EXAMPLE 81

3-(3-(5-Mercaptopentylthio)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate

To a solution of 3-(3-(5-chloropentylthio)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine (0.31 g, 1 mmol) in dimethylformamide (5 ml) was added sodium hydrogensulfide (0.35 g, 5 mmol) and the mixture was stirred at room temperature for 48 hours. Water was added and the free base extracted with ether. The free base was crystallized as the oxalate salt from acetone. Yield 50% . M.p. 106.degree.-107.degree. C. Compound 261.

In exactly the same manner the following compounds were prepared:

3-(3-(6-Mercaptohexylthio)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate. M.p. 105.degree.-106.degree. C. Compound 262.

3-(3-(4-Mercaptobutylthio)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate. M.p. 142.degree.-144.degree. C. Compound 263.

Claims

1. A compound of formula I ##STR7## wherein Z.sup.1 is oxygen or sulphur;

R is --Z.sup.2 --C.sub.3-7 -cycloalkyl optionally substituted with C.sub.1-6 -alkyl, --Z.sup.2 --C.sub.4-10 -(cycloalkylalkyl), --Z.sup.2 --C.sub.4-10 -(cycloalkenylalkyl), or --Z.sup.2 --C.sub.4-10 -(methylenecycloalkylalkyl), wherein Z.sup.2 is oxygen or sulfur;

R.sup.5 and R.sup.6 may be present at any appropriate position and independently are (1) hydrogen, (2) straight or branched C.sub.1-5 -alkyl, (3) straight or branched C.sub.2-5 -alkenyl, (4) straight or branched C.sub.2-5 -alkynyl, (5) straight or branched C.sub.1-10 -alkoxy, (6 straight or branched C.sub.1-5 -alkyl substituted with --OH, (7) --OH, (8) halogen, (9) --NH.sub.2 or (10) carboxy; and

R.sup.1 is hydrogen, straight or branched C.sub.1-5 -alkyl, straight or branched C.sub.2-5 -alkenyl or straight or branched C.sub.2-5 -alkynyl; or

a pharmaceutically acceptable salt thereof.

2. The compound according to claim 1 which is:

3-(3-(4-Cyclohexylbutoxy)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine;

3-(3-(4-Methylenecyclohexylmethyloxy)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine;

3-(3-(3-Cyclohexenylmethoxy)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine;

3-(3-(2-Methylcyclopropylmethoxy)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine;

3-(3-(3-Cyclohexylpropoxy)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine;

3-(3-(2-Cyclohexylethoxy)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine;

3-(3-(1-Cyclopropylmethylthio)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine;

3-(3-Cyclopentylthio-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine;

3-(3-Cyclohexylmethylthio-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine;

or a pharmaceutically acceptable salt thereof.

3. A pharmaceutical composition comprising a compound according to claim 1 together with a pharmaceutically acceptable carrier or diluent.

4. The pharmaceutical composition according to claim 3 in the form of an oral dosage unit or a parenteral dosage unit.

5. A method of treating Alzheimer's disease comprising administering to a subject in need thereof an effective amount of a compound according to claim 1.

6. A method of treating Alzheimer's disease comprising administering to a subject in need thereof a pharmaceutical composition according to claim 3.

7. A compound of formula I ##STR8## wherein Z.sup.1 is oxygen or sulphur;

R is --Z.sup.2 R.sup.2, wherein Z.sup.2 is oxygen or sulphur, and R.sup.2 is straight or branched C.sub.1-15 -alkyl, straight or branched C.sub.2-15 -alkenyl, or straight or branched C.sub.2-15 -alkynyl, each of which is substituted with --SH, --COOH, --NH--R.sup.2, or --NR.sup.2 R.sup.3 wherein R.sup.3 is straight or branched C.sub.1-15 -alkyl, straight or branched C.sub.2-15 -alkenyl, or straight or branched C.sub.2-15 -alkynyl;

R.sup.5 and R.sup.6 may be present at any appropriate position and independently are (1) hydrogen, (2) straight or branched C.sub.1-5 -alkyl, (3) straight or branched C.sub.2-5 -alkenyl, (4) straight or branched C.sub.2-5 -alkynyl, (5) straight or branched C.sub.1-10 -alkoxy, (6) straight or branched C.sub.1-5 -alkyl substituted with --OH, (7) --OH, (8) halogen, (9) --NH.sub.2 or (10) carboxy; and

R.sup.1 is hydrogen, straight or branched C.sub.1-5 -alkyl, straight or branched C.sub.2-5 -alkenyl or straight or branched C.sub.2-5 -alkynyl; or

a pharmaceutically acceptable salt thereof.

8. The compound according to claim 7 which is:

3-(3-Dimethylaminoethoxy-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine;

3-(3-Dimethylaminopropoxy-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine;

3-(3-(3-Carboxypropylthio)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine;

3-(3-(5-Carboxypentylthio)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine;

3-(3-(5-Mercaptopentylthio)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine;

3-(3-(6-Mercaptohexylthio)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine;

3-(3-(4-Mercaptobutylthio)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine;

or a pharmaceutically acceptable salt thereof.

9. The compound according to claim 7 which is:

3-(3-(3-Carboxypropoxy)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine; or a pharmaceutically acceptable salt thereof.

10. A pharmaceutical composition comprising a compound according to claim 7 together with a pharmaceutically acceptable carrier or diluent.

11. The pharmaceutical composition according to claim 10 in the form of an oral dosage unit or a parenteral dosage unit.

12. A method of treating Alzheimer's disease comprising administering to a subject in need thereof an effective amount of a compound according to claim 7.

13. A method of treating Alzheimer's disease comprising administering to a subject in need thereof a pharmaceutical composition according to claim 10.

14. A compound of formula I ##STR9## wherein Z.sup.1 is oxygen or sulphur;

R is --Z.sup.2 --X, wherein Z.sup.2 is oxygen or sulphur and X is a heterocyclic group selected from the group consisting of 1,3-dioxolanyl, pyridyl, thienyl, pyrrolidonyl, oxazolidonyl, thiazolidonyl, pyrrolidinyl, 1,2,5-thiadiazolyl, 1,3,4-thiadiazolyl, tetrazolyl, thiazolyl and oxazolyl, which heterocyclic group is optionally substituted at carbon or nitrogen atom(s) with straight or branched C.sub.1-6 -alkyl, C.sub.1-6 -alkoxy, C.sub.1-6 -alkylthio, phenyl, benzyl or pyridine; and

R.sup.5 and R.sup.6 may be present at any appropriate position and independently are (1) hydrogen, (2) straight or branched C.sub.1-5 -alkyl, (3) straight or branched C.sub.2-5 -alkenyl, (4) straight or branched C.sub.2-5 -alkynyl, (5) straight or branched C.sub.1-10 -alkoxy, (6) straight or branched C.sub.1-5 -alkyl substituted with --OH, (7) --OH, (8) halogen, (9) --NH.sub.2 or (10) carboxy;

R.sup.1 is hydrogen, straight or branched C.sub.1-5 -alkyl, straight or branched C.sub.2-5 alkenyl or straight or branched C.sub.2-5 -alkynyl; or

a pharmaceutically acceptable salt thereof.

15. The compound according to claim 14 wherein X is 1,2,5-thiadiazolyl which is substituted with C.sub.1-6 -alkoxy.

16. The compound according to claim 14 which is:

3-(3-(4-Ethoxy-1,2,5-thiadiazol-3-ylthio)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine;

3-(3-(4-Ethylthio-1,2,5-thiadiazol-3-ylthio)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine;

3-(3-(4-Butylthio-1,2,5-thiadiazol-3-ylthio)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine;

3-(3-(4-Propoxy-1,2,5-thiadiazol-3-ylthio)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine; or

a pharmaceutically acceptable salt thereof.

17. A pharmaceutical composition comprising a compound according to claim 14 together with a pharmaceutically acceptable carrier or diluent.

18. The pharmaceutical composition according to claim 17 in the form of an oral dosage unit or a parenteral dosage unit.

19. A method of treating Alzheimer's disease comprising administering to a subject in need thereof an effective amount of a compound according to claim 14.

20. A method of treating Alzheimer's disease comprising administering to a subject in need thereof a pharmaceutical composition according to claim 17.

21. A compound of formula I ##STR10## wherein Z.sup.1 is oxygen or sulphur;

R is --Z.sup.2 R.sup.2, wherein Z.sup.2 is oxygen or sulphur and R.sup.2 is an indenyl or naphthalylyl group;

R.sup.5 and R.sup.6 may be present at any appropriate position and independently are (1) hydrogen, (2) straight or branched C.sub.1-5 -alkyl, (3) straight or branched C.sub.2-5 -alkenyl, (4) straight or branched C.sub.2-5 -alkynyl, (5) straight or branched C.sub.1-10 -alkoxy, (6) straight or branched C.sub.1-5 -alkyl substituted with --OH, (7) --OH, (8) halogen, (9) --NH.sub.2 or (10) carboxy;

R.sup.1 is hydrogen, straight or branched C.sub.1-5 -alkyl, straight or branched C.sub.2-5 -alkenyl or straight or branched C.sub.2-5 -alkynyl; or

a pharmaceutically acceptable salt thereof.

22. The compound according to claim 21 which is:

3-(3-(2,3-Dihydro-1-indenyloxy)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine;

3-(3-(1,2,3,4-Tetrahydro-2-naphtalyloxy)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine; or

a pharmaceutically acceptable salt thereof.

23. A pharmaceutical composition comprising a compound according to claim 21 together with a pharmaceutically acceptable carrier or diluent.

24. The pharmaceutical composition according to claim 23 in the form of an oral dosage unit or a parenteral dosage unit.

25. A method of treating Alzheimer's disease comprising administering to a subject in need thereof an effective amount of a compound according to claim 21.

26. A method of treating Alzheimer's disease comprising administering to a subject in need thereof a pharmaceutical composition according to claim 23.

27. A compound of formula I ##STR11## wherein Z.sup.1 is oxygen or sulphur;

R is --Z.sup.2 --R.sup.2 CO--R.sup.3, --Z.sup.2 --R.sup.2 --CO.sub.2 --R.sup.3 or --Z.sup.2 --R.sup.2 --O.sub.2 C--R.sup.3, wherein Z.sup.2 is oxygen or sulphur, and R.sup.2 and R.sup.3 independently are unsubstituted, straight or branched C.sub.1-5 -alkyl, unsubstituted, straight or branched C.sub.2-5 -alkenyl, or unsubstituted, straight or branched C.sub.2-5 -alkynyl; and

R.sup.5 and R.sup.6 may be present at any appropriate position and independently are (1) hydrogen, (2) straight or branched C.sub.1-5 -alkyl, (3) straight or branched C.sub.2-5 -alkenyl, (4) straight or branched C.sub.2-5 -alkynyl, (5) straight or branched C.sub.1-10 -alkoxy, (6) straight or branched C.sub.1-5 -alkyl substituted with --OH, (7) --OH, (8) halogen, (9) --NH.sub.2 or (10) carboxy;

R.sup.1 is hydrogen, straight or branched C.sub.1-5 -alkyl, straight or branched C.sub.2-5 -alkenyl or straight or branched C.sub.2-5 -alkynyl; or

a pharmaceutically acceptable salt thereof.

28. The compound according to claim 27 which is:

3-(3-(5-Oxyhexyloxy)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine;

3-(3-Ethoxycarbonylpropylthio-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine;

3-(3-(1-Ethoxycarbonylpentylthio)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine; or

a pharmaceutically acceptable salt thereof.

29. A pharmaceutical composition comprising a compound according to claim 27 together with a pharmaceutically acceptable carrier or diluent.

30. The pharmaceutical composition according to claim 29 in the form of an oral dosage unit or a parenteral dosage unit.

31. A method of treating Alzheimer's disease comprising administering to a subject in need thereof an effective amount of a compound according to claim 27.

32. A method of treating Alzheimer's disease comprising administering to a subject in need thereof a pharmaceutical composition according to claim 29.

33. A compound which is:

3-(3-(4-Phenylthiobutylthio)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine; or a pharmaceutically acceptable salt thereof.

34. A compound which is:

3-(3-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine or a pharmaceutically acceptable salt thereof.