Method for using 2-aryloxyalkylaminobenzoxazoles and 2-aryloxyalkylaminobenzothiazoles as H3 antagonists

Abstract

The invention features methods of using pharmaceutically-active 2- or 3-aryl substituted imidazopyridines and derivatives.

Description

FIELD OF THE INVENTION

[0002] The invention relates to methods of using pharmaceutically-active fused heterobicyclic compounds to treat or prevent disorders and conditions mediated by the histamine H3 receptor.

BACKGROUND

[0003] The histamine H3 receptor is located as a presynaptic autoreceptor in the central nervous system and as a presynaptic heteroreceptor on serotonergic, noradrenergic, dopaminergic, and cholinergic neurons. The histamine H3 receptor is also located peripherally in tissues such as vascular smooth muscle cells.

[0004] Proposed uses of histamine H3 antagonists include the treatment or prevention of dementia, Alzheimer's disease (Panula et al. Abstr. Society Neuroscience, 1995, 21:1977), epilepsy (Yokoyama et al. Eur. J. Pharmacol., 1993, 234:129), sleep/wake disorders (Lin etal., Br. Res., 1990, 523, 325; Monti et al., Eur. J. Pharmacol., 1991,205, 283) including narcolepsy, insomnia, and jet lag, eating disorders (Machidori et al. Brain Research, 1992, 590:180), motion sickness, vertigo, attention deficit hyperactivity disorder, learning and memory disorders (Barnes et al. Abstr. Society Neuroscience, 1993,19:1813), schizophrenia (Schlickeret al. Naunyn Schmiedeberg's Arch. Pharmacol., 1996, 353:325), and sequelae associated with post-ischemic reperfusion and hypertension (Imamura et al., J. PharmacoL Expt. Ther., 1994, 271,1259). H3 antagonists are also useful to treat or prevent neurogenic inflammation such as migraine (McLeod et al., Abstr. Society Neuroscience, 1996, 22, 2010), asthma (Ichinose et al., Eur. J. Pharmacol., 989,174, 49), obesity, allergic rhinitis, substance abuse, bipolar disorders, manic disorders, and depression. Histamine H3 antagonists alone or in combination with a histamine H1 antagonist are believed to be useful in the treatment of upper airway allergic response or allergic rhinitis (see, e.g., U.S. Pat. Nos. 5,217,986, 5,352,707, and 5,869,479).

[0005] As noted, the prior art related to histamine H3 ligands was comprehensively reviewed recently (“The Histamine H3 Receptor-A Target for New Drugs”, Leurs, R., and Timmerman, H., (Editors), Elsevier, 1998). Within this reference the medicinal chemistry of histamine H3 agonists and antagonists was reviewed (see Krause et al. and Phillips et al., respectively). Thus the importance of an imidazole moiety containing only a single substitution in the 4 position was noted together with the deleterious effects of additional substitution on activity. Particularly methylation of the imidazole ring at any of the remaining unsubstituted positions was reported to strongly decrease activity.

[0006] More recently several publications have described histamine H3 ligands that do not contain an imidazole moiety. Examples include Ganellin et al Arch. Pharm. (Weinheim,Ger.) 1998, 331, 395; Walczynski et al Arch. Pharm. (Weinheim,Ger.) 1999, 332, 389; Walczynski et al Farmaco 1999, 684; Linney et al J. Med. Chem. 2000, 2362; U.S. Pat. No. 5,352,707; PCT Application WO99/42458, published Aug. 26,1999; and European Patent Application 0978512, published on Feb. 9, 2000.

SUMMARY OF THE INVENTION

[0007] The invention features the use of the compounds of formula (I) for the treatment and/or prevention of diseases and conditions mediated by the histamine 3 (H3) receptor. 1

[0008] R is O or S;

[0009] R1 is H, C1-4 alkyl, C1-4 alkoxy, Br, Cl, or l;

[0010] R2 and R3 are H or —O—(CH2)m—NR4R5, wherein one of R2 and R3 is H and the other is —O—(CH2)m—NR4R5, when R3 is —O—(CH2)m—NR4R5, R2 is independently H, halogen, C1-4 alkyl, or C1-4 alkoxy;

[0011] R4 and R5 are the same or different, and are C1-5 alkyl, C cycloalkyl, benzyl, benzyl substituted by C1-4 alkyl, C 14 alkoxy, Br, Cl, l, or R4 and R5 together with N are piperidyl, pyrrolidyl, imidazolyl, or N- substituted piperazyl, wherein the substituent is C1-4 alkyl, phenyl, or phenyl substituted with C1-3 alkoxy; n is 0 or 1; m is 2-6; with the provisos that when at least one of R and R1 is Ar; and both of R and R1 are not Ar;

[0012] or a pharmaceutically acceptable salt, ester, or amide thereof.

[0013] Many of the compounds are disclosed generically in U.S. Pat. No. 4,861,897. These compounds were first identified as having antisecretory properties. Additional features of the invention are disclosed in the following description and examples, and in the appended claims.

DETAILED DESCRIPTION

[0014] The invention features pharmaceutically active phenyl-substituted imidazopyridines and methods of making and using them. The description is organized as follows:

[0015] A. Terms

[0016] B. Compounds

[0017] C. Synthetic Methods

[0018] D. Uses

[0019] E. Synthetic Chemical Examples

[0020] F. Biological Examples

[0021] G. Other Embodiments

[0022] H. claims

[0023] A. Terms

[0024] The following terms are defined below and by their usage throughout this disclosure.

[0025] “Alkyl” includes straight chain and branched hydrocarbons with at least one hydrogen removed to form a radical group. Alkyl groups include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, t-butyl, 1-methylpropyl, pentyl, isopentyl, sec-pentyl, hexyl, heptyl, octyl, and so on.

[0026] “Alkoxy” includes a straight chain or branched alkyl group with a terminal oxygen linking the alkyl group to the rest of the molecule. Alkoxy includes methoxy, ethoxy, propoxy, isopropoxy, butoxy, t-butoxy, pentoxy and so on.

[0027] “halo” or “halogen” includes fluoro, chloro, bromo, and iodo, and preferably fluoro or chloro.

[0028] “patient” or “subject” includes mammals such as humans and animals (dogs, cats, horses, rats, rabbits, mice, non-human primates) in need of observation, experiment, treatment or prevention in connection with the relevant disease or condition. Preferably, the patient is a human.

[0029] “composition” includes a product comprising the specified ingredients in the specified amounts as well as any product which results directly or indirectly from combinations of the specified ingredients in the specified amounts.

[0030] Concerning the various radicals in this disclosure and in the claims, two general remarks are made. The first remark concerns valency. As with all hydrocarbon radicals, whether saturated, unsaturated or aromatic, and whether or not cyclic, straight chain, or branched, and also similarly with all heterocyclic radicals, each radical includes substituted radicals of that type and monovalent, bivalent, and multivalent radicals as indicated by the context of the claims. The context will indicate that the substituent is an alkylene or hydrocarbon radical with at least two hydrogen atoms removed (bivalent) or more hydrogen atoms removed (multivalent).

[0031] Second, radicals or structure fragments as defined herein are understood to include substituted radicals or structure fragments. Using “alkyl” as an example, “alkyl” should be understood to include substituted alkyl having one or more substitutions, such as between 1 and 5, 1 and 3, or 2 and 4 substituents. The substituents may be the same (dihydroxy, dimethyl), similar (chlorofluoro), or different (chlorobenzyl- or aminomethyl-substituted). Examples of substituted alkyl include haloalkyl (such as fluoromethyl, chloromethyl, difluoromethyl, perchloromethyl, 2-bromoethyl, and 3-iodocyclopentyl), hydroxyalkyl, aminoalkyl, nitroalkyl, alkylalkyl, and so on.

[0032] B. Compounds

[0033] One aspect of the invention features compounds of formula (I) as described in the Summary section above.

[0034] Preferred compounds of formula (I) include those compounds wherein: (a) R2 is H; (b) R3 is H; (c) R is O; (d) R1 is H; (e) R is S; (f) n is 1; (g) n is 0; (h) NR4R5 is a cyclic radical; (i) (h) wherein said cyclic radical is piperidyl or pyrrolinyl; 0) each of R4 and R5 is independently selected from ethyl, propyl, isopropyl, and butyl, including n-butyl, sec-butyl, tert-butyl, and isobutyl; (k) m is 2, 3, or 4, and more preferably wherein m is 3 or 4; (l) m is 3; (m) R1 is H, methyl, methoxy, Br, Cl, or l; (n) R2 is H, halogen, methyl, or methoxy, and preferably methyl; (o) or combinations thereof.

[0035] Additional preferred compounds include those wherein: R1 is H, methyl, methoxy, Br, Cl, or l; each of R4 and R5 is independently selected from ethyl, propyl, isopropyl, and butyl, or together with N are piperidyl or pyrrolinyl; m is 3 or 4; and each R2 is H, halogen, methyl, or methoxy.

[0036] Preferred compounds include: (E)-2-[2-(3-dibutylaminopropoxyphenyl)-ethenyl]benzoxazole; (E)-2-[2-[3-[3-(4-methylpiperazino)propoxy]-phenyl]ethenyl]benzoxazole; (E)-2-[2-(3-dipropylaminopropoxyphenyl)ethenyl]-benzoxazole; (E)-2-[2-(3-(1H-imidazol-1-yl)propoxyphenyl)ethenyl]-benzoxazole; (E)-2-[2-(3-dipropylaminobutoxyphenyl)ethenyl]benzoxazole; (E)-2-[2-(3-(1H-imidazol-1-yl)butoxyphenyl)ethenyl]benzoxazole; and (E)-2-[2-(3-(1H-imidazol-1-yl)butoxyphenyl)ethenyl]-6-methoxybenzoxazole; and acid addition salts thereof.

[0037] Preferred compounds also include: (E)-2-[2-(4-dibutylaminopropoxy-phenyl)ethenyl]benzoxazole; (E)-2-[2-(4-dipropylaminopropoxyphenyl)ethenyl]-benzoxazole; (E)-2-[2-(4-(1H-imidazol-1-yl)propoxyphenyl)ethenyl]-benzoxazole; (E)-2-[2-(4-diethylaminopropoxyphenyl)ethenyl]benzoxazole; (E)-2-[2-[4-(3-Piperidinopropoxy)phenyl]ethenyl]benzoxazole; (E)-2-[2-[4-(3-methylbenzylaminopropoxy)phenyl]ethenyl]benzoxazole; (E)-2-[2-[4-(2-methoxyphenyl)piperazinopropoxyphenyl]ethenyl]benzoxazole; (E)-2-[2-(4-dibutylaminopropoxyphenyl)ethenyl]-5-methylbenzoxazole; (E)-2-[2-(4-dibutylaminopropoxyphenyl)ethenyl]-6-methoxybenzoxazole; (E)-2-[2-(4-dibutylaminoethoxyphenyl)ethenyl]benzoxazole; (E)-2-[2-(4-dibutylamino-butoxyphenyl)ethenyl]benzoxazole; (E)-2-[2-(4-piperidinobutoxyphenyl)-ethenyllbenzoxazole; (E)-2-[2-(4-dipropylaminobutoxyphenyl)ethenyl]-benzoxazole; (E)-2-[2-(4-(1H-imidazol-1-yl)butoxyphenyl)ethenyl]benzoxazole; (E)-2-[2-(4-diethylaminobutoxyphenyl)ethenyl]benzoxazole; (E)-2-[2-(4-pyrrolidinobutoxyphenyl)ethenyl]benzoxazole; and (E)-2-[2-(4-(1H-imidazol-1-yl)pentoxyphenyl)ethenyl]benzoxazole; and acid addition salts thereof.

[0038] Additional preferred compounds include: (E)-2-[2-(3-chloro-4-dipropylaminobutoxyphenyl)ethenyl]benzoxazole, (E)-2-[2-(3,5-dimethoxy-4-dipropylaminopropoxyphenyl)ethenyl]benzoxazole and (E)-2-[2-(3,5-dimethyl-4-dipropylaminopropoxyphenyl)ethenyl]benzoxazole; and acid addition salts thereof.

[0039] More preferred compounds include: (E)-2-[2-(4-Piperidinopropoxy-phenyl)ethenyl]benzothiazole; (E)-2-[2-[4-(3-Piperidinopropoxy)phenyl]-ethenyl]benzoxazole; (E)-2-[2-(4-Piperidinobutoxyphenyl)ethenyl]benzoxazole; (E)-2-[2-(4-Diethylaminobutoxyphenyl)ethenyl]benzoxazole; (E)-2-[2-(4-Diethylaminopropoxyphenyl)ethenyl]benzoxazole; (E)-2-[2-(4-Pyrrolinobutoxy-phenyl)ethenyl]benzoxazole; E)-2-[2-(4-Dibutylaminobutoxyphenyl)-ethenyl]benzoxazole; and 2-(4-Dipropylaminopropoxyphenyl)benzothiazole and pharmaceutically acceptable salts thereof.

[0040] Other examples of compounds, and methods of making them, are provided in the examples below.

[0041] C. Synthetic Methods

[0042] The invention provides methods of making the disclosed compounds according to traditional organic synthetic methods as well as matrix or combinatorial synthetic methods. Traditional organic synthetic methods are described in U.S. Pat. No. 4,861,897, which is incorporated by reference in its entirety. Further guidance is found in Chemical Examples 1-8 below.

[0043] C. Uses

[0044] According to the invention, the disclosed compounds and compositions are useful for the amelioration of symptoms associated with, the treatment of, and/or the prevention of, the following conditions and diseases, or symptoms associated with them: dementia, Alzheimer's disease, narcolepsy, eating disorders, motion sickness, vertigo, attention deficit hyperactivity disorder, learning and memory disorders, schizophrenia, mild cognitive impairment, upper airway allergic response (allergic rhinitis), insomnia, jet lag, obesity, asthma, neurogenic inflammation, substance abuse, bipolar disorders, manic disorders, and depression. The invention also features pharmaceutical compositions, which include, without limitation, one or more of the disclosed compounds, and a pharmaceutically acceptable carrier or excipient.

[0045] 1. Dosages

[0046] Those skilled in the art will be able to determine, according to known methods, the appropriate dosage for a patient, taking into account factors such as age, weight, general health, the type of symptoms requiring treatment, and the use of other medications. An effective amount means that amount of pharmaceutical reagent (such as a prodrug, metabolic precursor, or active compound) that elicits the biological or medical response desired. In general, a therapeutically effective amount will be between 0.01 and 1000 mg/kg per day, preferably between 0.01 and 250 mg/kg body weight, and daily dosages will be between 0.50 and 5000 mg for an adult subject of normal weight. Capsules, tablets or other formulations (such as liquids and film-coated tablets) may be of between 0.20 and 100 mg, such as 0.20, 0.50, 1, 2, 3, and 10 mg can be administered according to the disclosed methods.

[0047] 2. Formulations

[0048] Dosage unit forms include tablets, capsules, pills, powders, granules, aqueous and nonaqueous oral solutions and suspensions, and parenteral solutions packaged in containers adapted for subdivision into individual doses. Dosage unit forms can also be adapted for various methods of administration, including controlled release formulations, such as subcutaneous implants. Administration methods include oral, rectal, parenteral (intravenous, intramuscular, subcutaneous), intracisternal, intravaginal, intraperitoneal, intravesical, local (drops, powders, ointments, gels or cream), and by inhalation (a buccal or nasal spray) as appropriate depending on the overall health and condition of the patient as determined by a physician or veterinary doctor.

[0049] Parenteral formulations include pharmaceutically acceptable aqueous or nonaqueous solutions, dispersion, suspensions, emulsions, and sterile powders for the preparation thereof. Examples of carriers include water, ethanol, polyols (propylene glycol, polyethylene glycol), vegetable oils, and injectable organic esters such as ethyl oleate. Fluidity can be maintained by the use of a coating such as lecithin, a surfactant, or maintaining appropriate particle size. Carriers for solid dosage forms include (a) fillers or extenders, (b) binders, (c) humectants, (d) disintegrating agents, (e) solution retarders, (f) absorption accelerators, (g) adsorbants, (h) lubricants, (i) buffering agents, and (j) propellants.

[0050] Compositions may also contain adjuvants such as preserving, wetting, emulsifying, and dispensing agents; antimicrobial agents such as parabens, chlorobutanol, phenol, and sorbic acid; isotonic agents such as a sugar or sodium chloride; absorption-prolonging agents such as aluminum monostearate and gelatin; and absorption-enhancing agents.

[0051] 3. Combination Therapy

[0052] The present invention also provides compositions and methods useful for the treatment of disorders or conditions modulated, preferably antagonized, by the histamine H3 receptor in combination with compounds that modulate other receptors including, but not limited to, histamine H1 and histamine H2 receptors. The present invention includes compounds and compositions useful in methods of combination therapy for the treatment of diseases or conditions modulated by the histamine H3 receptor in combination with compounds that are selective serotonin re-uptake inhibitors (SSRIs), such as PROZACTM, or are selective norepinephrine uptake inhibitors. Such combination methods include (a) administering the two or more pharmaceutical agents separately formulated and at separate times, and (b) administering the two or more agents simultaneously in a single formulation or in separate formulations administered more or less at the same time. For example, one aspect is a method of treatment comprising administering at least one histamine H3 receptor modulating compound disclosed herein and administering at least one compound selected from a histamine H1 receptor modulating compound, a histamine H2 receptor modulating compound, a selective serotonin reuptake inhibitor (such as PROZAC™), or a selective norepinephrine uptake inhibiting compound.

[0053] 4. Related Compounds

[0054] The invention provides the disclosed compounds and closely related, pharmaceutically acceptable forms of the disclosed compounds, such as salts, esters, amides, acids, hydrates or solvated forms thereof; masked or protected forms; and racemic mixtures, or enantiomerically or optically pure forms.

[0055] Pharmaceutically acceptable salts, esters, and amides include carboxylate salts (e.g., C1-8, alkyl, cycloalkyl, aryl, heteroaryl, or non-aromatic heterocyclic) amino acid addition salts, esters, and amides which are within a reasonable benefit/risk ratio, pharmacologically effective and suitable for contact with the tissues of patients without undue toxicity, irritation, or allergic response. Representative salts include hydrobromide, hydrochloride, sulfate, bisulfate, nitrate, acetate, oxalate, valerate, oleate, palmitate, stearate, laurate, borate, benzoate, lactate, phosphate, tosylate, citrate, maleate, fumarate, succinate, tartrate, naphthylate, mesylate, glucoheptonate, lactiobionate, and laurylsulfonate. These may include alkali metal and alkali earth cations such as sodium, potassium, calcium, and magnesium, as well as non-toxic ammonium, quaternary ammonium, and amine cations such as tetramethyl ammonium, methylamine, trimethylamine, and ethylamine. See example, S. M. Berge, et al., “Pharmaceutical Salts,” J. Pharm. Sci., 1977, 66:1-19 which is incorporated herein by reference. Representative pharmaceutically acceptable amides of the invention include those derived from ammonia, primary C1-6 alkyl amines and secondary di (C1-6 alkyl) amines. Secondary amines include 5- or 6-membered heterocyclic or heteroaromatic ring moieties containing at least one nitrogen atom and optionally between 1 and 2 additional heteroatoms. Preferred amides are derived from ammonia, C1-3alkyl primary amines, and di (C1-2 alkyl)amines. Representative pharmaceutically acceptable esters of the invention include C1-7alkyl, C5-7 cycloalkyl, phenyl, and phenyl(C1-6)alkyl esters. Preferred esters include methyl esters.

[0056] The invention also includes disclosed compounds having one or more functional groups (e.g., hydroxyl, amino, or carboxyl) masked by a protecting group. See, e.g., Greene and Wuts, Protective Groups in Organic Synthesis, 3rd ed., (1999) John Wiley & Sons, NY. Some of these masked or protected compounds are pharmaceutically acceptable; others will be useful as intermediates. Synthetic intermediates and processes disclosed herein, and minor modifications thereof, are also within the scope of the invention.

[0057] Hydroxyl Protecting Groups

[0058] Protection for the hydroxyl group includes methyl ethers, substituted methyl ethers, substituted ethyl ethers, substitute benzyl ethers, and silyl ethers.

[0059] Substituted Methyl Ethers

[0060] Examples of substituted methyl ethers include methyoxymethyl, methylthiomethyl, t-butylthiomethyl, (phenyidimethylsilyl)methoxymethyl, benzyloxymethyl, p-methoxybenzyloxymethyl, (4-methoxyphenoxy)methyl, guaiacolmethyl, t-butoxymethyl, 4-pentenyloxymethyl, siloxymethyl, 2-methoxyethoxymethyl, 2,2,2-trichloroethoxymethyl, bis(2-chloroethoxy)methyl, 2-(trimethylsilyl)ethoxymethyl, tetrahydropyranyl, 3-bromotetrahydropyranyl, tetrahydrothiopyranyl, 1-methoxycyclohexyl, 4-methoxytetrahydropyranyl, 4-methoxytetrahydrothiopyranyl, 4-methoxytetrahydrothiopyranyl S,S-dioxido, 1-[(2-chloro-4-methyl)phenyl]-4-methoxypiperidin-4-yl, 1,4-dioxan-2-yl, tetrahydrofuranyl, tetrahydrothiofuranyl and 2,3,3a,4,5,6,7,7a-octahydro-7,8,8-trimethyl-4,7-methanobenzofuran-2-yl.

[0061] Substituted Ethyl Ethers

[0062] Examples of substituted ethyl ethers include 1-ethoxyethyl, 1-(2-chloroethoxy)ethyl, 1-methyl-1-methoxyethyl, 1-methyl-1-benzyloxyethyl, 1-methyl-1-benzyloxy-2-fluoroethyl, 2,2,2-trichloroethyl, 2-trimethylsilylethyl, 2-(phenylselenyl)ethyl, t-butyl, allyl, p-chlorophenyl, p-methoxyphenyl, 2,4-dinitrophenyl, and benzyl.

[0063] Substituted Benzyl Ethers

[0064] Examples of substituted benzyl ethers include p-methoxybenzyl, 3,4-dimethoxybenzyl, o-nitrobenzyl, p-nitrobenzyl, p-halobenzyl, 2,6-dichlorobenzyl, p-cyanobenzyl, p-phenylbenzyl, 2- and 4-picolyl, 3-methyl-2-picolyl N-oxido, diphenylmethyl, p, p′-dinitrobenzhydryl, 5-dibenzosuberyl, triphenylmethyl, a-naphthyidiphenylmethyl, p-methoxyphenyidiphenylmethyl, di(p-methoxyphenyl)phenylmethyl, tri(p-methoxyphenyl)methyl, 4-(4′-bromophenacyloxy)phenyldiphenylmethyl, 4,4′,4″-tris(4,5-dichlorophthalimidophenyl)methyl, 4,4′,4″-tris(levulinoyloxyphenyl)methyl, 4,4′,4″-tris(benzoyloxyphenyl)methyl, 3-(Imidazol-1-ylmethyl)bis(4 ′,4″-dimethoxyphenyl)methyl, 1,1-bis(4-methoxyphenyl)-1′-pyrenylmethyl, 9-anthryl, 9-(9-phenyl)xanthenyl, 9-(9-phenyl-10-oxo)anthryl, 1,3-benzodithiolan-2-yl, and benzisothiazolyl S,S-dioxido.

[0065] Silyl Ethers

[0066] Examples of silyl ethers include trimethylsilyl, triethylsilyl, triisopropylsilyl, dimethylisopropylsilyl, diethylisopropylsilyl, dimethylthexylsilyl, t-butyidimethylsilyl, t-butyldiphenylsilyl, tribenzylsilyl, tri-p-xylylsilyl, triphenylsilyl, diphenylmethylsilyl, and t-butylmethoxyphenylsilyl.

[0067] Esters

[0068] In addition to ethers, a hydroxyl group may be protected as an ester. Examples of esters include formate, benzoylformate, acetate, chloroacetate, dichloroacetate, trichloroacetate, trifluoroacetate, methoxyacetate, triphenylmethoxyacetate, phenoxyacetate, p-chlorophenoxyacetate, p-P- phenylacetate, 3-phenylpropionate, 4-oxopentanoate(levulinate), 4,4-(ethylenedithio)pentanoate, pivaloate, adamantoate, crotonate, 4-methoxycrotonate, benzoate, p-phenylbenzoate, 2,4,6-trimethylbenzoate(mesitoate) Carbonates Examples of carbonate protecting groups include methyl, 9-fluorenylmethyl, ethyl, 2,2,2-trichloroethyl, 2-(trimethylsilyl)ethyl, 2-(phenylsulfonyl)ethyl, 2-(triphenylphosphonio)ethyl, isobutyl, vinyl, allyl, p-nitrophenyl, benzyl, p-methoxybenzyl, 3,4-dimethoxybenzyl, o-nitrobenzyl, p-nitrobenzyl, S-benzyl thiocarbonate, 4-ethoxy-1-naphthyl, and methyl dithiocarbonate.

[0069] Assisted Cleavage

[0070] Examples of assisted cleavage include 2-iodobenzoate, 4-azidobutyrate, 4-nitro-4-methylpentanoate, o-(dibromomethyl)benzoate, 2-formylbenzenesulfonate, 2-(methylthiomethoxy)ethyl carbonate, 4-(methylthiomethoxy)butyrate, and 2-(methylthiomethoxymethyl)benzoate.

[0071] Miscellaneous Esters

[0072] Examples of miscellaneous esters include 2,6-dichloro-4-methylphenoxyacetate, 2,6-dichloro-4-(1,1,3,3-tetramethylbutyl)phenoxyacetate, 2,4-bis(1,1-dimethylpropyl)phenoxyacetate, chlorodiphenylacetate, isobutyrate, monosuccinoate, (E)-2-methyl-2-butenoate(tigloate), o-(methoxycarbonyl)benzoate, p-P-benzoate, α-naphthoate, nitrate, alkyl N,N,N′,N′-tetramethylphosphorodiamidate, N-phenylcarbamate, borate, dimethylphosphinothioyl, and 2,4-dinitrophenylsulfenate

[0073] Sulfonates

[0074] Examples of sulfonates include sulfate, methanesulfonate(mesylate), benzylsulfonate, and tosylate.

[0075] Protection for 1,2- and 1,3-Diols

[0076] Cyclic Acetals and Ketals

[0077] Examples of cyclic acetals and ketals include methylene, ethylidene, 1-t-butylethylidene, 1-phenylethylidene, (4-methoxyphenyl)ethylidene, 2,2,2-trichloroethylidene, acetonide (isopropylidene), cyclopentylidene, cyclohexylidene, cycloheptylidene, benzylidene, p-methoxybenzylidene, 2,4-dimethoxybenzylidene, 3,4-dimethoxybenzylidene, and 2-nitrobenzylidene.

[0078] Cyclic Ortho Esters

[0079] Examples of cyclic ortho esters include methoxymethylene, ethoxymethylene, dimethoxymethylene, 1-methoxyethylidene, 1-ethoxyethylidine, 1,2-dimethoxyethylidene, a-methoxybenzylidene, 1-(N,N-dimethylamino)ethylidene derivative, a-(N,N-dimethylamino)benzylidene derivative, and 2-oxacyclopentylidene.

[0080] Silyl Derivatives

[0081] Examples of silyl derivatives include di-t-butylsilylene group, and 1,3-(1,1,3,3-tetraisopropyldisiloxanylidene) derivative.

[0082] Amino Protecting Groups

[0083] Protection for the amino group includes carbamates, amides, and special —NH protective groups.

[0084] Examples of carbamates include methyl and ethyl carbamates, substituted ethyl carbamates, assisted cleavage carbamates, photolytic cleavage carbamates, urea-type derivatives, and miscellaneous carbamates.

[0085] Carbamates

[0086] Examples of methyl and ethyl carbamates include methyl and ethyl, 9-fluorenylmethyl, 9-(2-sulfo)fluorenylmethyl, 9-(2,7-dibromo)fluorenylmethyl, 2,7-di-t-butyl-[9-(10,1 0-dioxo-10,10,10,1 0-tetrahydrothioxanthyl)]methyl, and 4-methoxyphenacyl.

[0087] Substituted Ethyl

[0088] Examples of substituted ethyl carbamates include 2,2,2-trichloroethyl, 2-trimethylsilylethyl, 2-phenylethyl, 1-(1-adamantyl)-1-methylethyl, 1,1-dimethyl-2-haloethyl, 1,1-dimethyl-2,2- dibromoethyl, 1,1-dimethyl-2,2,2-trichloroethyl, 1-methyl-1-(4-biphenylyl)ethyl, 1-(3,5-di-t-butylphenyl)-1-methylethyl, 2-(2′- and 4′-pyridyl) ethyl, 2-(N,N-dicycl ohexylcarboxamido)ethyl, t-butyl, 1-adamantyl, vinyl, allyl, 1-isopropylall yl, cinnamyl, 4-nitrocinnamyl, 8-quinolyl, N-hydroxypiperidinyl, alkyldithio, benzyl, p-methoxybenzyl, p-nitrobenzyl, p-bromobenzyl, p-chlorobenzyl, 2,4-dichlorobenzyl, 4-methylsulfinylbenzyl, 9-anthrylmethyl and diphenylmethyl.

[0089] Assisted Cleavage

[0090] Examples of assisted cleavage include 2-methylthioethyl, 2-methylsulfonylethyl, 2-(p-toluenesulfonyl)ethyl, [2-(1,3-dithianyl)]methyl, 4-methylthiophenyl, 2,4-dimethylthiophenyl, 2-phosphonioethyl, 2-triphenylphosphonioisopropyl, 1,1-dimethyl-2-cyanoethyl, m-chloro-p-acyloxybenzyl, p-(dihydroxyboryl)benzyl, 5-benzisoxazolylmethyl, and 2-(trifluoromethyl)-6-chromonylmethyl.

[0091] Photolytic Cleavage

[0092] Examples of photolytic cleavage include m-nitrophenyl, 3,5-dimethoxybenzyl, o-nitrobenzyl, 3,4-dimethoxy-6-nitrobenzyl, and phenyl(o-nitrophenyl)methyl.

[0093] Urea-type Derivatives

[0094] Examples of urea-type derivatives include phenothiazinyl-(10)-carbonyl derivative, N′-p-toluenesulfonylaminocarbonyl, and N′-phenylaminothiocarbonyl.

[0095] Miscellaneous Carbamates

[0096] Examples of miscellaneous carbamates include t-amyl, S-benzyl thiocarbamate, p-cyanobenzyl, cyclobutyl, cyclohexyl, cyclopentyl, cyclopropyl methyl, p-decyloxybenzyl, diisopropyl methyl, 2,2-dimethoxycarbonylvinyl, o-(N,N-dimethylcarboxamido)benzyl, 1,1-dimethyl-3-(N,N-dimethylcarboxamido)propyl, 1,1-dimethylpropynyl, di(2-pyridyl)methyl, 2-furanylmethyl, 2-iodoethyl, isobornyl, isobutyl, isonicotinyl, p-(p′-methoxyphenylazo)benzyl, 1-methylcyclobutyl, 1-methylcyclohexyl, 1-methyl-1-cyclopropylmethyl, 1-methyl-1-(3,5-dimethoxyphenyl)ethyl, 1-methyl-1-(p-phenylazophenyl)ethyl, 1-methyl-1-phenylethyl, 1-methyl-1-(4-pyridyl)ethyl, phenyl, p-(phenylazo)benzyl, 2,4,6-tri-t-butylphenyl, 4-(trimethylammonium)benzyl, and 2,4,6-trimethylbenzyl.

[0097] Examples of amides include:

[0098] Amides

[0099] N-formyl, N-acetyl, N-chloroacetyl, N-trichloroacetyl, N-trifluoroacetyl, N-phenylacetyl, N-3-phenylpropionyl, N-picolinoyl, N-3-pyridylcarboxamide, N-benzoylphenylalanyl derivative, N-benzoyl, N-p-phenylbenzoyl.

[0100] Assisted Cleavage

[0101] N-o-nitrophenylacetyl, N-o-nitrophenoxyacetyl, N-acetoacetyl, (N′-dithiobenzyloxycarbonylamino)acetyl, N-3-(p-hydroxyphenyl)propionyl, N-3-(o-nitrophenyl)propionyl, N-2-methyl-2-(o-nitrophenoxy)propionyl, N-2-methyl-2-(o-phenylazophenoxy)propionyl, N-4-chlorobutyryl, N-3-methyl-3-nitrobutyryl, N-o-nitrocinnamoyl, N-acetylmethionine derivative, N-o-nitrobenzoyl, N-o-(benzoyloxymethyl)benzoyl, and 4,5-diphenyl-3-oxazolin-2-one.

[0102] Cyclic Imide Derivatives

[0103] N-phthalimide, N-dithiasuccinoyl, N-2,3-diphenylmaleoyl, N-2,5-dimethylpyrrolyl, N-1,1,4,4-tetramethyldisilylazacyclopentane adduct, 5-substituted 1,3-dimethyl-1,3,5-triazacyclohexan-2-one, 5-substituted 1,3-dibenzyl-1,3,5-triazacyclohexan-2-one, and 1-substituted 3,5-dinitro-4-pyridonyl.

[0104] Special-NH Protective Groups

[0105] Examples of special NH protective groups include

[0106] N-Alkyl and N-Aryl Amines

[0107] N-methyl, N-allyl, N-[2-(trimethylsilyl)ethoxy]methyl, N-3,-acetoxypropyl, N-(1-isopropyl4-nitro-2-oxo-3-pyrrolin-3-yl), quaternary ammonium salts, N-benzyl, N-di(4-methoxyphenyl)methyl, N-5-dibenzosuberyl, N-triphenylmethyl, N-(4-methoxyphenyl)diphenylmethyl, N-9-phenylfluorenyl, N-2,7-dichloro-9-fluorenylmethylene, N-ferrocenylmethyl, and N-2-picolylamine N′-oxide.

[0108] Imine Derivatives

[0109] N-1,1-dimethylthiomethylene, N-benzylidene, N-p-methoxybenzylidene, N-diphenylmethylene, N-[(2-pyridyl)mesityl]methylene, and N-(N′,N′-dimethylaminomethylene).

[0110] Protection for the Carbonyl Group

[0111] Acyclic Acetals and Ketals

[0112] Examples of acyclic acetals and ketals include dimethyl, bis(2,2,2-trichloroethyl), dibenzyl, bis(2-nitrobenzyl) and diacetyl.

[0113] Cyclic Acetals and Ketals

[0114] Examples of cyclic acetals and ketals include 1,3-dioxanes, 5-methylene-1,3-dioxane, 5,5-dibromo-1,3-dioxane, 5-(2-pyridyl)-1,3-dioxane, 1,3-dioxolanes, 4-bromomethyl-1,3-dioxolane, 4-(3-butenyl)-1,3-dioxolane, 4-phenyl-1,3-dioxolane, 4-(2-nitrophenyl)-1,3-dioxolane, 4,5-dimethoxymethyl-1,3-dioxolane, 0,O′-phenylenedioxy and 1 ,5-dihydro-3H-2,4-benzodioxepin.

[0115] Acyclic Dithio Acetals and Ketals

[0116] Examples of acyclic dithio acetals and ketals include S,S′-dimethyl, S,S′-diethyl, S,S′-dipropyl, S,S′-dibutyl, S,S′-dipentyl, S,S′-diphenyl, S,S′-dibenzyl and S,S′-diacetyl.

[0117] Cyclic Dithio Acetals and Ketals

[0118] Examples of cyclic dithio acetals and ketals include 1,3-dithiane, 1,3-dithiolane and 1,5-dihydro-3H-2,4-benzodithiepin.

[0119] Acyclic Monothio Acetals and Ketals

[0120] Examples of acyclic monothio acetals and ketals include O-trimethylsilyl-S-alkyl, O-methyl-S-alkyl or -S-phenyl and O-methyl-S-2-(methylthio)ethyl.

[0121] Cyclic Monothio Acetals and Ketals

[0122] Examples of cyclic monothio acetals and ketals include 1,3-oxathiolanes.

[0123] Miscellaneous Derivatives

[0124] O-Substituted Cyanohydrins

[0125] Examples of O-substituted cyanohydrins include O-acetyl, O-trimethylsilyl, O-1-ethoxyethyl and O-tetrahydropyranyl.

[0126] Substituted Hydrazones

[0127] Examples of substituted hydrazones include N,N-dimethyl and 2,4-dinitrophenyl.

[0128] Oxime Derivatives

[0129] Examples of oxime derivatives include O-methyl, O-benzyl and O-phenylthiomethyl.

[0130] Imines

[0131] Substituted Methylene Derivatives, Cyclic Derivatives

[0132] Examples of substituted methylene and cyclic derivatives include oxazolidines, 1-methyl-2-(1′-hyd roxyalkyl)imidazoles, N, N′-dimethylimidazolidines, 2,3-dihydro-1,3-benzothiazoles, diethylamine adducts, and methylaluminum bis(2,6-di-t-butyl4-methylphenoxide)(MAD)complex.

[0133] Monoprotection of Dicarbonyl Compounds

[0134] Selective Protection Of α-and β-Diketones

[0135] Examples of selective protection of α-and β-diketones include enamines, enol acetates, enol ethers, methyl, ethyl, 1-butyl, piperidinyl, morpholinyl, 4-methyl-1,3-dioxolanyl, pyrrolidinyl, benzyl, S-butyl, and trimethylsilyl.

[0136] Cyclic Ketals, Monothio and Dithio Ketals

[0137] Examples of cyclic ketals, monothio and dithio ketals include bismethylenedioxy derivatives and tetramethylbismethylenedioxy derivatives.

[0138] Protection for the Carboxyl Group

[0139] Esters

[0140] Examples of esters include the following.

[0141] Substituted Methyl Esters

[0142] Examples of substituted methyl esters include 9-fluorenylmethyl, methoxymethyl, methylthiomethyl, tetrahyd ropyranyl, tetrahydrofuranyl, methoxyethoxymethyl, 2-(trimethylsilyl)ethoxymethyl, benzyloxymethyl, phenacyl, p-bromophenacyl, β-methylphenacyl, p-methoxyphenacyl, carboxamidomethyl, and N-phthalimidomethyl.

[0143] 2-Substituted Ethyl Esters

[0144] Examples of 2-substituted ethyl esters include 2,2,2-trichloroethyl, 2-haloethyl, ω-chloroalkyl, 2-(trimethylsilyl)ethyl, 2-methylthioethyl, 1,3-dithianyl-2-methyl, 2-(p-nitrophenylsulfenyl)ethyl, 2-(p-toluenesulfonyl)ethyl, 2-(2′-pyridyl)ethyl, 2-(diphenylphosphino)ethyl, 1-methyl-1-phenylethyl, t-butyl, cyclopentyl, cyclohexyl, allyl, 3-buten-1-yl, 4-(trimethylsilyl)-2-buten-1-yl, cinnamyl, α-methylcinnamyl, phenyl, p-(methylmercapto)phenyl and benzyl.

[0145] Substituted Benzyl Esters

[0146] Examples of substituted benzyl esters include triphenylmethyl, diphenylmethyl, bis(o-nitrophenyl)methyl, 9-anthrylmethyl, 2-(9,10-dioxo)anthrylmethyl, 5-dibenzosuberyl, 1-pyrenylmethyl, 2-(trifluoromethyl)-6-chromylmethyl, 2,4,6-trimethylbenzyl, p-bromobenzyl, o-nitrobenzyl, p-nitrobenzyl, p-methoxybenzyl, 2,6-dimethoxybenzyl, 4-(methylsulfinyl)benzyl, 4-sulfobenzyl, piperonyl, 4-picolyl and p-P-benzyl.

[0147] Silyl Esters

[0148] Examples of silyl esters include trimethylsilyl, triethylsilyl, t-butyldimethylsilyl, 1-propyidimethylsilyl, phenyidimethylsilyl and di-t-butylmethylsilyl.

[0149] Activated Esters

[0150] Examples of activated esters include thiols.

[0151] Miscellaneous Derivatives

[0152] Examples of miscellaneous derivatives include oxazoles, 2-alkyl-1,3-oxazolines, 4-alkyl-5-oxo-1,3-oxazolidines, 5-alkyl-4-oxo-1,3-dioxolanes, ortho esters, phenyl group and pentaaminocobalt(III) complex.

[0153] Stannyl Esters

[0154] Examples of stannyl esters include triethylstannyl and tri-n-butylstannyl.

[0155] Amides and Hydrazides

[0156] Amides

[0157] Examples of amides include N,N-dimethyl, pyrrolidinyl, piperidinyl, 5,6-dihydrophenanthridinyl, o-nitroanilides, N-7-nitroindolyl, N-8-Nitro-1,2,3,4-tetrahydroquinolyl, and p-P-benzenesulfonamides.

[0158] Hydrazides

[0159] Examples of hydrazides include N-phenyl and N,N′-diisopropyl hydrazides.

[0160] D. Synthetic Chemical Examples

[0161] Additional experimental descriptions of the compounds of the invention are found in the Examples of U.S. Pat. No. 4,861,897, incorporated herein by reference in its entirety. Examples 3, 4, 6, 7, 8, and 9 below correspond to Examples 1,2, 13, 7, 8, and 14 of the '897 patent, respectively, and are provided as general guidance.

EXAMPLE 1

(E)-2-[2-(4-Dibutylaminopropoxyphenyl)ethenyl]benzoxazole

[0162] To a suspension of sodium hydride (50% in oil, 3.9 g, 82 mmol) in dimethylformamide (100 ml) was added p-hydroxybenzaldehyde (5.0 g, 41 mmol). The mixture was stirred at room temperature under an atmosphere of nitrogen for one hour, then treated dropwise with 1-bromo-3-chloropropane (8.1 ml, 82 mmol). The mixture was stirred at room temperature for 12 hours, quenched with methanol and filtered through Celite. The filtrate was dissolved in diethyl ether (500 ml), washed with water (3×200 ml) and dried over Na2 SO4. The ether layer was concentrated to give 6.1 g (80% yield) of 4-chloropropoxybenzaldehyde as a yellow liquid. 1H NMR (CDCl3): δ 9.95 (s, 1H), 7.85 (d, J=8.1 Hz, 2H), 7.01 (d, J=8.1 Hz, 2H), 4.21 (t, J=5 Hz, 2H), 3.81 (t, J=5 Hz, 2H), 1.26 (m, 2H).

[0163] To a solution of this product (5.0 g, 25 mmol) and 2-methylbenzoxazole (3.1 ml, 25 mmol) in dimethylsulfoxide (25 ml) was added a 50% aqueous sodium hydroxide solution (15 ml). The solution was stirred at room temperature for 24 hours, diluted with ice water (1 L), and the resulting precipitate was collected by filtration. The precipitate was washed with water and dried in vacuo to give (E)-2-[2-(4-chloropropoxyphenyl)ethenyl]benzoxazole (C) (6.4 g, 79% yield) as a yellow solid, mp 82°-83° C. IR(KBr): 1600 cm−1 MS: 313(M+). 1H NMR (CDCl3): δ 7.88-6.79 (m, 10H), 4.19 (t, J=5 Hz, 2H), 3.79 (t, J=5 Hz, 2H), 2.31 (m, 2H).

[0164] Theor. C18H16 NO2 Cl: C, 68.90; H, 5.14; N, 4.46. Found: C, 69.20; H, 5.46; N, 4.27.

[0165] A solution of this product (6.0 g, 19 mmol) in 60 ml of dibutylamine was heated to 150° C. for 12 hours. The excess dibutylamine was removed by distillation and the resulting oil was purified by flash chromatography (SiGel, 9:1 CHCl3 -MeOH) to give 5.8 g (75% yield) of the free base of the title compound. The HCl salt was prepared by the addition of concentrated hydrochloric acid to a solution of the free base in methanol, concentrated, and recrystallized from acetone to give the HCl salt of the title compound as a yellow solid, mp 153°-154° C. IR(KBr): 3400,1595 cm−1 MS: 406(MH+). 1H NMR (CDCl3): δ 7.99-6.81 (m, 10H), 4.15 (t, J=5 Hz, 2H), 3.09 (m, 6H), 2.44 (m, 2H), 1.99-0.87 (m, 16H).

[0166] Theor. C26H.34 N2 O2.HCl.1/2 H2O: C, 69.08; H, 8.03; N, 6.19. Found: C, 68.89; H, 7.92; N, 6.24.

EXAMPLE 2

(E)-2-[2-(4-Dibutylaminopropoxyphenyl)ethenyl]benzothiazole

[0167] The title compound was prepared in accordance with Example 1 starting with 4-chloropropoxybenzaldehyde (17.0 g, 86 mmol) and using 2-methylbenzothiazole (11 ml, 86 mmol) in place of 2-methylbenzoxazole to give 25.0 g (89% yield) of (E)-2-[2-(4-chloropropoxyphenyl)ethenyl]benzothiazole (F) as a yellow solid, mp 97°-99° C. 1NMR (CDCl3): δ 8.15-6.91 (m, 10H), 4.15 (t, J=5.2 Hz, 2H), 3.81 (t, J=5.2 Hz, 2H), 2.21 (m, 2H).

[0168] Reaction of this product (10.0 g, 30 mmol) with dibutylamine produced 8.4 g (66% yield) of the free base of the title compound which was converted to the HCl salt, mp 181°-182° C. IR(KBr): 3400, 1595 cm−1 MS: 422(M+). 1H NMR (CDCl3): δ 7.88-6.81 (m, 10H), 4.12 (t, J=5.3 Hz, 2H), 3.02-2.59 (m, 6H), 2.25-0.84 (m, 16H).

[0169] Theor. C26H34 N2 OS.2HCl.2H2 O: C, 58.75; H, 7.58; N, 6.10. Found: C, 58.52; H, 7.14; N, 5.26.

EXAMPLE 3

[0170] 2

(E)-2-[2-(4-Piperidinopropoxyphenyl)ethenyl]benzothiazole Ki=15 nM

[0171] The procedure of Example 2 was followed starting with (F) of Example 2 (3.0 g, 9.8 mmol) and using piperidine in place of dibutylamine to produce 1.9 g (51% yield) of the free base of the named compound which was converted to the HCl salt, mp 215°-217° C. IR(KBr): 3400,1595 cm−1. MS: 379(MH+). 1H NMR (CD3 OD): δ 7.64-6.48 (m, 10H), 3.72 (t, J=5.2 Hz, 2H), 2.65 (m, 6H), 1.98 (m, 2H), 1.32 (m, 6H).

[0172] Theor. C23H26 N2 OS.1HCl.3/2H2 O: C, 62.49; H, 6.84; N, 6.34. Found: C, 62.53; H, 6.94; N, 6.26.

EXAMPLE 4

[0173] 3

(E)-2-[2-[4-(3-Piperidinopropoxy)phenyl]ethenyl]benzoxazole Ki=13 nM

[0174] The procedure of Example 1 was followed starting with (C) of Example 1 (2.0 g, 6.4 mmol) and using piperidine in place of dibutylamine to produce 1.1 g, (41% yield) of the named compound as the HCl salt, mp 127°-128° C. IR(KBr): 3400,1600 cm−1. MS: 363(MH+). 1H NMR (CD3 OD): δ 7.89-6.81 (m, 10H), 4.24 (t, J=5.5 Hz, 2H), 2.65 (m, 6H), 1.75 (m, 8H).

[0175] Theor. C23H26 N2 O2.HCl.H2 O: C, 66.26; H, 6.77; N, 6.72. Found: C, 66.01; H, 6.92; N, 6.98.

EXAMPLE 5

(E)-2-[2-(4-Dibutylaminobutoxyphenyl)ethenyl]benzoxazole

[0176] The procedure of Example 1 was followed with p-hydroxybenzaldehyde (5.0 g, 41 mmol) and using 1-bromo-4-chlorobutane (9.5 ml, 82 mmol) in place of 1-bromo-3-chloropropane to give 8.9 g (97% yield) of 4-chlorobutoxy-benzaldehyde. 1H NMR (CDCl3) δ 9.85 (s, 1H), 7.82 (d, J=8.1 Hz, 2H), 6.99 (d, J=8.1 Hz, 2H), 4.04 (t, J=5.3 Hz, 2H), 3.59 (t, J=5.3 Hz, 2H), 1.91 (m, 4H).

[0177] Condensation of this product (4.0 g, 19 mmol) with 2-methylbenzoxazole (2.3 ml, 19 mmol) gave (E)-2-[2-(4-chlorobutoxyphenyl)ethenyl]benzoxazole (D) (4.5 g, 72% yield) as an off-white solid, mp 92°-93° C. 1H NMR (CDCl3): δ 7.88-6.81 (m, 1OH), 4.08 (t, J=5.1 Hz, 2H), 3.34 (t, J=5.3 Hz, 2H), 2.55 (m, 4H).

[0178] Reaction of this product (3.0 g, 9.1 mmol) with dibutylamine produced the named compound (0.4 g, 11% yield) which was converted to the HCl salt, mp 172°-174° C. IR(KBr): 3400, 1600 cm−1. MS: 421(MH+). 1H NMR (CD3 OD):δ 7.82-6.85 (m, 10H), 4.02 (t, J=5.2 Hz, 2H), 3.11 (m, 6H), 1.98-0.84 (m, 18H).

[0179] Theor. C27H36 N2 O2HCl.H2 O: C, 68.26; H, 8.27; N, 5.6. Found: C, 68.31; H, 7.91; N, 5.48.

EXAMPLE 6

[0180] 4

(E)-2-[2-(4-Piperidinobutoxyphenyl)ethenyl]benzoxazole Ki=34 nM

[0181] The title compound was prepared as described in Example 5 starting with (D) of Example 5 (2.5 g, 7.6 mmmol) and using piperidine in place of dibutylamine to produce 1.2 g (42% yield) of the title compound as the HCl salt, mp 230′-232° C. IR(KBr): 1600 cm−1. MS: 377(MH+). 1H NMR (DMSO): δ 7.91-6.95 (m, 10H), 3.99 (t, J=5.2 Hz, 2H), 3.10 (m, 6H), 1.75 (m, 10H).

[0182] Theor. C24H28 N2 O2.HCl: C, 69.80; H, 7.08; N, 6.78. Found: C, 70.12; H, 7.09; N, 6.93.

EXAMPLE 7

[0183] 5

(E)-2-[2-(4-Diethylaminobutoxyphenyl)ethenyl]benzoxazole Ki=48 nM

[0184] The procedure of Example 5 was followed starting with (D) of Example 5 (2.5 g, 7.6 mmol) and using diethylamine in place of dibutylamine to produce 0.32 g (12% yield) of the named compound as the HCl salt, mp 219°-220° C. IR(KBr): 3400, 1600 cm−1. MS: 365(MH+). 1H NMR (CDCl3): δ 8.25-6.82 (m, 10H), 4.02 (t, J=5.4 Hz, 2H), 3.14 (m, 6H), 1.99 (m, 4H), 1.36 (m, 6H).

[0185] Theor. C23H28 N2 O3.HCl.H2 O: C, 65.94; H, 7.46; N, 6.69. Found: C, 66.12; H, 7.25; N, 6.57.

[0186] EXAMPLE 8 6

(E)-2-[2-(4-Diethylaminopropoxyphenyl)ethenyl]benzoxazole Ki=31 nM

[0187] The title compound was prepared as described in Example 1 starting with (C) of Example 1 (2.0 g, 6.4 mmol) and using diethylamine in place of dibutylamine to produce 2.8 g (85% yield) diethylamine in place of dibutylamine to produce 2.8 g (85% yield) of the title compound as the HCl salt, mp 225°-226° C. IR(KBr): 1600 cm−1. MS: 351(MH+). 1H NMR (CD3 OD): δ 7.99-6.81 (m, 10H), 4.24 (t, J=5.7 Hz, 2H), 3.09 (m, 6H), 2.44 (m, 2H), 0.87 (m, 6H).

[0188] Theor. C22H26 N2 O2.HCl: C, 68.29; H, 7.03; N, 7.24. Found: C, 68.34; H, 7.34; N, 6.91.

EXAMPLE 9

[0189] 7

(E)-2-[2-(4-Pyrrolinobutoxyphenyl)ethenyl]benzoxazole Ki=17 nM

[0190] The title compound was prepared as described in Example 5 starting with (D) of Example 5 (3.0 g, 9.1 mmol) and using pyrrolidine in place of dibutylamine to produce 1.8 g (55% yield) of the title compound as the HCl salt, mp 229°-232° C. IR(KBr): 3400, 1600 cm−1. MS: 363(MH+). 1H NMR (CD3 OD): δ 7.91-6.87 (m, 10H), 4.04 (t, J=5.2 Hz, 2H), 3.21 (m, 6H), 1.99 (m, 8H).

[0191] Theor. C23H26 N2 O2.HCl.H2 O: C, 65.25; H, 7.01; N, 6.72. Found: C, 65.48; H, 7.24; N, 6.99.

EXAMPLE 10

E)-2-[2-(4-Dibutylaminobutoxyphenyl)ethenyl]benzoxazole

[0192] The procedure of Example 1 was followed with p-hydroxybenzaldehyde (5.0 g, 41 mmol) and using 1-bromo-4-chlorobutane (9.5 ml, 82 mmol) in place of 1-bromo-3-chloropropane to give 8.9 g (97% yield) of 4-chlorobutoxybenzaldehyde. 1H NMR (CDCl3) δ 9.85 (s, 1H), 7.82 (d, J=8.1 Hz, 2H), 6.99 (d, J=8.1 Hz, 2H), 4.04 (t, J=5.3 Hz, 2H), 3.59 (t, J=5.3 Hz, 2H), 1.91 (m, 4H).

[0193] Condensation of this product (4.0 g, 19 mmol) with 2-methylbenzoxazole (2.3 ml, 19 mmol) gave (E)-2-[2-(4-chlorobutoxyphenyl)ethenyl]benzoxazole (D) (4.5 g, 72% yield) as an off-white solid, mp 92°-93° C. 1H NMR (CDCl3): δ 7.88-6.81 (m, 10H), 4.08 (t, J=5.1 Hz, 2H), 3.34 (t, J=5.3 Hz, 2H), 2.55 (m, 4H).

[0194] Reaction of this product (3.0 g, 9.1 mmol) with dibutylamine produced the named compound (0.4 g, 11% yield) which was converted to the HCl salt, mp 172°-174° C. IR(KBr): 3400, 1600 cm−1. MS: 421(MH+). 1H NMR (CD3 OD): δ 7.82-6.85 (m, 10H), 4.02 (t, J=5.2 Hz, 2H), 3.11 (m, 6H), 1.98-0.84 (m, 18H).

[0195] Theor. C27H36 N2 O2.HCl.H2O: C, 68.26; H, 8.27; N, 5.6. Found: C, 68.31; H, 7.91; N, 5.48.

EXAMPLE 11

[0196] 8

2-(4-Dipropylaminopropoxyphenyl)benzothiazole Ki=173 nM

[0197] The title compound was prepared as described in Example 43 of U.S. Pat. No. 4,861,897 starting with (I) of Example 43 (2.0 g, 6.3 mmol) and using dipropylamine in place of dibutylamine to produce 0.41 g (19% yield) of the title compound as the HCl salt, mp 142°-143° C. IR(KBr): 3400, 1600 cm−1. MS: 369(MH+). 1H NMR (CDCl3): δ 8.19-6.95 (m, 8H), 4.19 (t, J=5.1 Hz, 2H), 3.01 (m, 6H), 2.64-0.82 (m, 12H).

[0198] Theor. C22H28 N2 OS.2HCl.1/2H2 O: C, 58.65; H, 6.94; N, 6.22. Found: C, 58.55; H, 6.85; N, 6.17.

EXAMPLE 12

[0199] 9

(E)-2-[2-(3,5-Dimethyl-4-dipropylaminobutoxyphenyl)ethenyl]benzothiazole Ki=1000 nM

[0200] The title compound was prepared according to the procedure of Example 5 above using 4-chlorobutoxy-3, 5-dimethylbenzaldehyde in place of 4-chlorobutoxybenzaldehyde and using 2-methylbenzothiazole in place of 2-methylbenzoxazole. 4-Chlorobutoxy-3, 5-dimethylbenzaldehyde was prepared from 3,5-dimethyl-4-hydroxybenzaldehyde according to the procedure Example 1 above.

[0201] F. Biological Examples

[0202] In the present invention receptor binding was determined using the human histamine H3 receptor (See Lovenberg et al Mol. Pharmacol. 1999, 1107). Screening using the human receptor is particularly important for the identification of new therapies for the treatment of human disease. Conventional binding assays for example are determined using rat synaptosomes (Garbarg et al J. Pharmacol. Exp. Ther. 1992, 263, 304), rat cortical membranes (West et al Mol. Pharmacol. 1990, 610), and guinea pig brain (Korte et al Biochem. Biophys. Res. Commun. 1990, 978). Only limited studies have been performed previously using human tissue but these allude to significant differences in the pharmacology of rodent and primate receptors (West et al Eur. J. Pharmacol. 1999, 233).

BIOLOGICAL EXAMPLE 1

[0203] 1(A) Transfection of Cells with Human Histamine Receptor

[0204] A 10 cm tissue culture dish with a confluent monolayer of SK-N-MC cells was split two days prior to transfection. Using sterile technique the media was removed and the cells were detached from the dish by the addition of trypsin. One fifth of the cells were then placed onto a new 10 cm dish. Cells were grown in a 37° C. incubator with 5% CO2 in Minimal Essential Media Eagle with 10% Fetal Bovine Serum. After two days cells were approximately 80% confluent. These were removed from the dish with trypsin and pelleted in a clinical centrifuge. The pellet was then re-suspended in 400 μL complete media and transferred to an electroporation cuvette with a 0.4 cm gap between the electrodes (Bio-Rad #165-2088). One microgram supercoiled H3 receptor CDNA was added to the cells and mixed. The voltage for the electroporation was set at 0.25 kV, the capacitance is set at 960 μF.

[0205] After electroporation the cells were diluted into 10 mL complete media and plated onto four 10 cm dishes. Due to the variability in the efficiency of electroporation, four different concentrations of cells were plated. The ratios used were: 1:20, 1:10, and 1:5, with the remainder of the cells being added to the fourth dish. The cells were allowed to recover for 24 hours before adding the selection media (complete media with 600 μg/ml G418). After 10 days dishes were analyzed for surviving colonies of cells. Dishes with well-isolated colonies were used. Cells from individual colonies were isolated and tested. SK-N-MC cells were used because they give efficient coupling for inhibition of adenylate cyclase. The clones that gave the most robust inhibition of adenylate cyclase in response to histamine were used for further study.

[0206] 1(B) [3H]-N-methylhistamine Binding

[0207] Cell pellets from histamine H3 receptor-expressing SK-N-MC cells were homogenized in 20 mM TrisHCl/0.5 mM EDTA. Supernatants from a 800 g spin were collected, reccentrifuged at 30,000 g for 30 minutes. Pellets were rehomogenized in 50 mM Tris/5 mM EDTA (pH 7.4). Membranes were incubated with 0.8 nM [3H]-N-methylhistamine plus/minus test compounds for 45 minutes at 25° C. and harvested by rapid filtration over GF/C glass fiber filters (pretreated with 0.3% polyethylenimine) followed by four washes with ice cold buffer. Filters were dried, added to 4 mL scintillation cocktail and then counted on a liquid scintillation counter. Non-specific binding was defined with 10 μM histamine according to Chen and Prusoff, Biochem. Pharmacol. 1973, 22:3099. KI values were calculated based on a KD of 800 pM and a ligand concentration ([L]) of 800 pM according to the formula:

KI=(IC50)/(1+([L]/(KD)).

[0208] KI values are provided in the examples above.

[0209] E. Other Embodiments

[0210] The features and advantages of the invention are apparent to one of ordinary skill in the art. Based on this disclosure, including the summary, detailed description, background, examples, and claims, one of ordinary skill in the art will be able to make modifications and adaptations to various conditions and usages. These other embodiments are also within the scope of the invention.

Claims

1. A method for treating disorders mediated by the histamine H3 receptor in a patient, said method comprising administering to the patient a pharmaceutically effective amount of compound of formula (I):

2. A method of claim 1, wherein said condition is improved by administering an H3 antagonist.

3. A method of claim 1, wherein said compound has a formula wherein R2 is H.

4. A method of claim 1, wherein said compound has a formula wherein R3 is H.

5. A method of claim 1, wherein R is O.

6. A method of claim 5, wherein R1 is H.

7. A method of claim 1, wherein R is S.

8. A method of claim 1, wherein n is 1.

9. A method of claim 1, wherein said compound has a formula wherein NR4R5 is a cyclic radical.

10. A method of claim 9, wherein said cyclic radical is piperidyl or pyrrolinyl.

11. A method of claim 1, wherein said compound has a formula wherein each of R4 and R5 is independently selected from ethyl, propyl, isopropyl, and butyl.

12. A method of claim 1, wherein m is 2, 3, or 4.

13. A method of claim 12, wherein m is 3.

14. A method of claim 1, wherein R1 is H, methyl, methoxy, Br, Cl, or I; each of R4 and R5 is independently selected from ethyl, propyl, isopropyl, and butyl, or together with N are piperidyl or pyrrolinyl; m is 3 or 4; and each R2 is H, halogen, methyl, or methoxy.

15. A method of claim 1, wherein said compound is selected from: (E)-2-[2-(4-Piperidinopropoxyphenyl)ethenyl]benzothiazole; (E)-2-[2-[4-(3-Piperidinopropoxy)phenyl]ethenyl]benzoxazole; (E)-2-[2-(4-Piperidinobutoxyphenyl)ethenyl]benzoxazole; (E)-2-[2-(4-Diethylaminobutoxyphenyl)ethenyl]benzoxazole; (E)-2-[2-(4-Diethylaminopropoxyphenyl)ethenyl]benzoxazole; (E)-2-[2-(4-Pyrrolinobutoxyphenyl)ethenyl]benzoxazole; (E)-2-[2-(4-Dibutylaminobutoxyphenyl)ethenyl]benzoxazole; and 2-(4-Dipropylaminopropoxyphenyl)benzothiazole.

16. A method of claim 1, wherein said compound is selected from (E)-2-[2-(3-dibutylaminopropoxyphenyl)ethenyl]benzoxazole; (E)-2-[2-[3-[3-(4-methylpiperazino)propoxy]phenyl]ethenyl]-benzoxazole; (E)-2-[2-(3-dipropylaminopropoxyphenyl)ethenyl]benzoxazole; (E)-2-[2-(3-(1H-imidazol-1-yl)propoxyphenyl)ethenyl]benzoxazole; (E)-2-[2-(3-dipropylaminobutoxyphenyl)ethenyl]benzoxazole; (E)-2-[2-(3-(1H-imidazol-1-yl)butoxyphenyl)ethenyl]benzoxazole; and (E)-2-[2-(3-(1H-imidazol-1-yl)butoxyphenyl)ethenyl]-6-methoxybenzoxazole;.

17. A method of claim 1, wherein said compound is selected from (E)-2-[2-(4-d ibutylaminopropoxyphenyl)ethenyl]benzoxazole; (E)-2-[2-(4-dipropylaminopropoxyphenyl)ethenyl]]benzoxazole; (E)-2-[2-(4-(1H-imidazol-1-yl)propoxyphenyl)ethenyl]benzoxazole; (E)-2-[2-(4-diethylaminopropoxyphenyl)ethenyl]benzoxazole; (E)-2-[2-[4-(3-Piperidinopropoxy)phenyl]ethenyl]benzoxazole; (E)-2-[2-[4-(3-methylbenzylaminopropoxy)phenyl]ethenyl]-benzoxazole; (E)-2-[2-[4-(2-methoxyphenyl)piperazinopropoxyphenyl]ethenyl]-benzoxazole; (E)-2-[2-(4-dibutylaminopropoxyphenyl)ethenyl]-5-methylbenzoxazole; (E)-2-[2-(4-dibutylaminopropoxyphenyl)ethenyl]-6-methoxybenzoxazole; (E)-2-[2-(4-dibutylaminoethoxyphenyl)ethenyl]benzoxazole; (E)-2-[2-(4-dibutylaminobutoxyphenyl)ethenyl]benzoxazole; (E)-2-[2-(4-piperidinobutoxyphenyl)ethenyl]benzoxazole; (E)-2-[2-(4-dipropylaminobutoxyphenyl)ethenyl]benzoxazole; (E)-2-[2-(4-(1H-imidazol-1-yl)butoxyphenyl)ethenyl]benzoxazole; (E)-2-[2-(4-diethylaminobutoxyphenyl)ethenyl]benzoxazole; (E)-2-[2-(4-pyrrolidinobutoxyphenyl)ethenyl]benzoxazole; and (E)-2-[2-(4-(1H-imidazol-1-yl)pentoxyphenyl)ethenyl].

18. A method of claim 1, wherein said compound is selected from (E)-2-[2-(3-chloro4-dipropylaminobutoxyphenyl)ethenyl]-benzoxazole, (E)-2-[2-(3,5-dimethoxy-4-dipropylamino-propoxyphenyl)ethenyl]benzoxazole; and (E)-2-[2-(3,5-dimethyl-4-dipropylaminopropoxyphenyl)ethenyl].

19. A method for treating a patient with a central nervous system disorder, said method comprising administering to the patient a pharmaceutically-effective amount of a compound of formula (I).

20. A method of claim 19, wherein said compound has a formula wherein R1 is H, methyl, methoxy, Br, Cl, or I; each of R4 and R5 is independently selected from ethyl, propyl, isopropyl, and butyl, or together with N are piperidyl or pyrrolinyl; m is 3 or 4; and each R2 is H, halogen, methyl, or methoxy.

21. A method of claim 19, wherein said compound is selected from: (E)-2-[2-(4-Piperidinopropoxyphenyl)ethenyl]benzothiazole; (E)-2-[2-[4-(3-Piperidinopropoxy)phenyl]ethenyl]benzoxazole; (E)-2-[2-(4-Piperidinobutoxyphenyl)ethenyl]benzoxazole; (E)-2-[2-(4-Diethylaminobutoxyphenyl)ethenyl]benzoxazole; (E)-2-[2-(4-Diethylaminopropoxyphenyl)ethenyl]benzoxazole; (E)-2-[2-(4-Pyrrolinobutoxyphenyl)ethenyl]benzoxazole; E)-2-[2-(4-Dibutylaminobutoxyphenyl)ethenyl]benzoxazole; 2-(4-Dipropylaminopropoxyphenyl)benzothiazole.

22. A method of claim 19, wherein said central nervous system disorder is selected from sleep/wake disorders, arousal/vigilance disorders, dementia, Alzheimer's disease, epilepsy, narcolepsy, eating disorders, motion sickness, vertigo, attention deficit hyperactivity disorder, learning and memory disorders, mild cognitive impairment, and schizophrenia.

23. A method of claim 19, wherein said central nervous system disorder is selected from Alzheimer's disease, epilepsy, eating disorders, learning and memory disorders, migraine, sleep/wake disorders, allergic rhinitis, schizophrenia, mild cognitive impairment, and asthma.

24. A method of claim 19, wherein said disorder is selected from sleep/wake disorders, arousal/vigilance disorders, attention deficit hyperactivity disorder, and learning and memory disorders.

25. A method of claim 19, wherein said compound is selected from (E)-2-[2-(3-dibutylaminopropoxyphenyl)ethenyl]benzoxazole; (E)-2-[2-[3-[3-(4-methylpiperazino)propoxy]phenyl]ethenyl]-benzoxazole; (E)-2-[2-(3-dipropylaminopropoxyphenyl)ethenyl]benzoxazole; (E)-2-[2-(3-(1H-imidazol-1-yl)propoxyphenyl)ethenyl]benzoxazole; (E)-2-[2-(3-dipropylaminobutoxyphenyl)ethenyl]benzoxazole; (E)-2-[2-(3-(1H-imidazol-1-yl)butoxyphenyl)ethenyl]benzoxazole; and (E)-2-[2-(3-(1H-imidazol-1-yl)butoxyphenyl)ethenyl]-6-methoxybenzoxazole.

26. A method of claim 19, wherein said compound is selected from (E)-2-[2-(4-dibutylaminopropoxyphenyl)ethenyl]benzoxazole; (E)-2-[2-(4-dipropylaminopropoxyphenyl)ethenyl]]benzoxazole; (E)-2-[2-(4-(1H-imidazol-1-yl)propoxyphenyl)ethenyl]benzoxazole; (E)-2-[2-(4-diethylaminopropoxyphenyl)ethenyl]benzoxazole; (E)-2-[2-[4-(3-Piperidinopropoxy)phenyl]ethenyl]benzoxazole; (E)-2-[2-[4-(3-methylbenzylaminopropoxy)phenyl]ethenyl]-benzoxazole; (E)-2-[2-[4-(2-methoxyphenyl)piperazinopropoxyphenyl]ethenyl]-benzoxazole; (E)-2-[2-(4-dibutylaminopropoxyphenyl)ethenyl]-5-methyl-benzoxazole; (E)-2-[2-(4-dibutylaminopropoxyphenyl)ethenyl]-6-methoxy-benzoxazole; (E)-2-[2-(4-dibutylaminoethoxyphenyl)ethenyl]benzoxazole; (E)-2-[2-(4-dibutylaminobutoxyphenyl)ethenyl]benzoxazole; (E)-2-[2-(4-piperidinobutoxyphenyl)ethenyl]benzoxazole; (E)-2-[2-(4-dipropylaminobutoxyphenyl)ethenyl]benzoxazole; (E)-2-[2-(4-(1H-imidazol-1-yl)butoxyphenyl)ethenyl]benzoxazole; (E)-2-[2-(4-diethylaminobutoxyphenyl)ethenyl]benzoxazole; (E)-2-[2-(4-pyrrolidinobutoxyphenyl)ethenyl]benzoxazole; and (E)-2-[2-(4-(1H-imidazol-1-yl)pentoxyphenyl)ethenyl].

27. A method of claim 19, wherein said compound is selected from (E)-2-[2-(3-chloro-4-dipropylaminobutoxyphenyl)ethenyl]-benzoxazole, (E)-2-[2-(3,5-dimethoxy-4-dipropylaminopropoxy-phenyl)ethenyl]benzoxazole and (E)-2-[2-(3,5-dimethyl-4-dipropylaminopropoxyphenyl)ethenyl]benzoxazole.

28. A method for treating a patient with an upper airway allergic response, said method comprising administering to the patient a pharmaceutically-effective amount of a compound of formula (I).

29. A method of claim 28, wherein R1 is H, methyl, methoxy, Br, Cl, or I; each of R4 and R5 is independently selected from ethyl, propyl, isopropyl, and butyl, or together with N are piperidyl or pyrrolinyl; m is 3 or 4; and each R2 is H, halogen, methyl, or methoxy.

30. A method of claim 28, wherein said compound is selected from: (E)-2-[2-(4-Piperidinopropoxyphenyl)ethenyl]benzothiazole; (E)-2-[2-[4-(3-Piperidinopropoxy)phenyl]ethenyl]benzoxazole; (E)-2-[2-(4-Piperidinobutoxyphenyl)ethenyl]benzoxazole; (E)-2-[2-(4-Diethylaminobutoxyphenyl)ethenyl]benzoxazole; (E)-2-[2-(4-Diethylaminopropoxyphenyl)ethenyl]benzoxazole; (E)-2-[2-(4-Pyrrolinobutoxyphenyl)ethenyl]benzoxazole; E)-2-[2-(4-Dibutylaminobutoxyphenyl)ethenyl]benzoxazole; 2-(4-Dipropylaminopropoxyphenyl)benzothiazole.

31. A method of claim 28, wherein said compound is selected from (E)-2-[2-(3-dibutylaminopropoxyphenyl)ethenyl]benzoxazole; (E)-2-[2-[3-[3-(4-methylpiperazino)propoxy]phenyl]ethenyl]-benzoxazole; (E)-2-[2-(3-dipropylaminopropoxyphenyl)ethenyl]benzoxazole; (E)-2-[2-(3-(1H-imidazol-1-yl)propoxyphenyl)ethenyl]benzoxazole; (E)-2-[2-(3-dipropylaminobutoxyphenyl)ethenyl]benzoxazole; (E)-2-[2-(3-(1H-imidazol-1-yl)butoxyphenyl)ethenyl]benzoxazole; and (E)-2-[2-(3-(1H-imidazol-1-yl)butoxyphenyl)ethenyl]-6-methoxybenzoxazole.

32. A method of claim 28, wherein said compound is selected from (E)-2-[2-(4-dibutylaminopropoxyphenyl)ethenyl]benzoxazole; (E)-2-[2-(4-dipropylaminopropoxyphenyl)ethenyl]]benzoxazole; (E)-2-[2-(4-(1H-imidazol-1-yl)propoxyphenyl)ethenyl]benzoxazole; (E)-2-[2-(4-diethylaminopropoxyphenyl)ethenyl]benzoxazole; (E)-2-[2-[4-(3-Piperidinopropoxy)phenyl]ethenyl]benzoxazole; (E)-2-[2-[4-(3-methylbenzylaminopropoxy)phenyl]ethenyl]-benzoxazole; (E)-2-[2-[4-(2-methoxyphenyl)piperazinopropoxy-phenyl]ethenyl]benzoxazole; (E)-2-[2-(4-dibutylaminopropoxy-phenyl)ethenyl]-5-methylbenzoxazole; (E)-2-[2-(4-dibutylaminopropoxyphenyl)ethenyl]-6-methoxybenzoxazole; (E)-2-[2-(4-dibutylaminoethoxyphenyl)ethenyl]benzoxazole; (E)-2-[2-(4-dibutylaminobutoxyphenyl)ethenyl]benzoxazole; (E)-2-[2-(4-piperidinobutoxyphenyl)ethenyl]benzoxazole; (E)-2-[2-(4-dipropylaminobutoxyphenyl)ethenyl]benzoxazole; (E)-2-[2-(4-(1H-imidazol-1-yl)butoxyphenyl)ethenyl]benzoxazole; (E)-2-[2-(4-d iethylaminobutoxyph enyl )ethenyl] be nzoxazole; (E)-2-[2-(4-pyrrolidinobutoxyphenyl)ethenyl]benzoxazole; and (E)-2-[2-(4-(1H-imidazol-1-yl)pentoxyphenyl)ethenyl]benzoxazole.

33. A method of claim 28, wherein said compound is selected from (E)-2-[2-(3-chloro-4-dipropylaminobutoxyphenyl)-ethenyl]benzoxazole, (E)-2-[2-(3,5-dimethoxy-4-dipropylaminopropoxyphenyl)ethenyl]benzoxazole; and (E)-2-[2-(3,5-dimethyl-4-dipropylaminopropoxyphenyl)ethenyl]-benzoxazole.