Claims
- 1. A compound having the formula: ##STR3## wherein R.sup.2 is a 3 to 6 membered oxygen or sulphur containing heterocyclic ring which may be saturated or fully or partially unsaturated and which may be substituted by one or more C.sub.1 -C.sub.4 alkyl groups or halogen atoms;
- R.sup.4 is hydrogen or methyl.
- 2. A composition for the treatment or prevention of parasitic infections in humans and animals which comprises a compound of claim 1 together with an inert diluent or carrier.
- 3. A composition as claimed in claim 2 in the form of a liquid drench or an oral or injectable formulation.
- 4. A composition as claimed in claim 2 in the form of an animal feedstuff or in the form of a premix or supplement for addition to animal feed.
- 5. A method of combating insect or parasite infections or infestations in humans and animals and agricultural or horticultural pest infestations, which comprises applying an effective amount of a compound according to claim 1 to the organism responsible for said infection or infestation or to the location thereof.
- 6. A compound according to claim 1 wherein R.sup.2 is thienyl.
- 7. A compound according to claim 6 wherein R.sup.2 is thien-2-yl.
- 8. A compound according to claim 1 wherein R.sup.2 is furyl.
- 9. A compound according to claim 8 wherein R.sup.2 is 2-furyl.
- 10. A compound according to claim 1 wherein R.sup.2 is tetrahydrothien-3-yl.
- 11. A compound according to claim 1 wherein R.sup.2 is tetrahydrothiopyran-4-yl.
Priority Claims (1)
| Number |
Date |
Country |
Kind |
| 8721647 |
Sep 1987 |
GBX |
|
CROSS REFERENCE TO RELATED APPLICATION
This application is a division of application Ser. No. 227,921, filed Aug. 3, 1988, now abandoned.
This invention relates to antiparasitic agents and in particular to compounds related to the milbemycins but having a novel substituent at the 25-position and to a process for their preparation.
The milbemycins are a group of broad spectrum antiparasitic agents related to the avermectins but differing from them in lacking the sugar residues at the 13-position. This invention relates specifically to the subgroup of milbemycins which are characterised by the unsaturation present in the 25-position substituent produced by fermenting strains of the microorganisms Streptomyces cyaneogriseus ssp noncyanogenus NRRL 15773 or Streptomyces thermoarchaensis NCIB 12015. The morphological and cultural properties of the strains NRRL 15773 and NCIB 12015 are described in detail in the European Patent Application No. 0170006 and UK Patent Application GB No. 2 166 436A respectively. The first of these patent applications describes the isolation and characterisation of thirteen individual milbemycins designated LL-F28249.alpha.-.nu. and the second describes a complex of six components designated S541 Factors A-F.
According to the specification of our European patent application No. 0214731, published Mar. 18, 1987, we describe a process for preparing novel avermectins having a modified group at the 25-position, by adding a carboxylic acid or derivative thereof to a fermentation of an avermectin producing organism.
We have now discovered that by adding certain specified carboxylic acids, or derivatives thereof, to a fermentation of the above milbemycin producing organisms it is possible to obtain novel compounds, related to the complexes LL-F28249 and S541, but having an unnatural substituent group at the 25-position.
Surprisingly, however, the group is not directly attached to the 25-position, as in the avermectins, but is linked via a 2-propenyl group.
The novel compounds are highly active antiparasitic agents having particular utility as anthelmintics, ectoparasiticides, insecticides and acaricides.
Conventional chemical transformation reactions can be used to prepare further derivatives from these compounds. Thus, according to the invention there are provided compounds having the formula (I): ##STR1## wherein either R is hydrogen and R.sup.1 is hydroxy or R and R.sup.1 are taken together and are oxo;
R.sup.2 is a C.sub.3 -C.sub.8 straight or branched-chain alkyl, alkenyl or alkynyl group which may optionally contain an oxygen or sulphur atom as part of the chain, or a C.sub.3 -C.sub.8 cycloalkyl or cycloalkenyl group, or a 3 to 6 membered oxygen or sulphur containing heterocyclic ring which may be saturated or fully or partially unsaturated and which may optionally be substituted by one or more C.sub.1 -C.sub.4 alkyl groups or halogen atoms;
R.sup.3 is methyl or ethyl;
R.sup.4 is hydrogen or methyl; either R.sup.5 is hydrogen or hydroxy and R.sup.6 is methyl or hydroxymethyl, or the two groups R.sup.5 and R.sup.6 are taken together and are --O--CH.sub.2 --;
R.sup.7 is hydrogen, methyl or ethyl; and
R.sup.8 is hydrogen or halogen; with the proviso that when R.sup.2 is branched chain alkyl it is not isopropyl.
In the above definition halogen means fluorine, chlorine, bromine or iodine.
A preferred class of compounds have the formula (II): ##STR2## wherein R.sup.2 and R.sup.4 are as previously defined.
Particularly preferred are compounds of the formula (II) wherein R.sup.2 is (1-methylthio)ethyl, 2-pent-4-enyl or 2-butyl.
In accordance with the invention, compounds of the formula (I) wherein R.sup.8 is hydrogen are prepared by fermenting a strain of the milbemycin producing organism Streptomyces cyaneogriseus subsp. noncyanogenus NRRL 15773 or Streptomyces thermoarchaensis NCIB 12015 in the presence of the appropriate carboxylic acid of the formula R.sup.2 CO.sub.2 H, wherein R.sup.2 is as previously defined, or a salt, ester or amide thereof, or oxidative precursor therefor.
The acid is added to the fermentation either at the time of inoculation or at intervals during the fermentation. Production of the compounds of formula (I) may be monitored by removing samples from the fermentation, extracting with an organic solvent and following the appearance of the compound of formula (I) by chromatography, for example using high pressure liquid chromatography. Incubation is continued until the yield of the compound of formula (I) has been maximised, generally for a period of from 4 to 6 days.
A preferred level of each addition of the carboxylic acid or derivative thereof is between 0.05 and 10 grams per liter. The best yields of the compounds of formula (I) are obtained by gradually adding the acid to the fermentation, for example by daily additions of the acid or derivative thereof over a period of several days. The acid is preferably added as a salt, such as the sodium or ammonium salt, but may be added as an ester, such as the methyl or ethyl ester or as an amide. Alternative substrates which may be used in the fermentation are derivatives which are oxidative precursors for the carboxylic acids; thus, for example suitable substrates would be aminoacids of the formula R.sup.2 CH(NH.sub.2)CO.sub.2 H, glyoxylic acids of the formula R.sup.2 COCO.sub.2 H, methylamine derivatives of the formula R.sup.2 CH.sub.2 NH.sub.2, substituted lower alkanoic acids of the formula R.sup.2 (CH.sub.2).sub.n CO.sub.2 H wherein n is 2, 4 or 6, methanol derivatives of the formula R.sup.2 CH.sub.2 OH or aldehydes of the formula R.sup.2 CHO, wherein R.sup.2 is as previously defined. The media used for the fermentation may be a conventional complex media containing assimilable sources of carbon, nitrogen and other trace elements.
After fermentation for a period of several days at a temperature preferably in the range of from 24.degree. to 33.degree. C., the fermentation broth is centrifuged or filtered and the mycelial cake is extracted with acetone or methanol. The solvent extract is concentrated and the desired product is then extracted into a water-immiscible organic solvent, such as methylene chloride, ethyl acetate, chloroform, butanol or methyl isobutyl ketone. The solvent extract is concentrated and the crude product containing the compounds of formula (I) is further purified as necessary by chromatography, for example using preparative reverse phase, high pressure liquid chromatography.
The product is generally obtained as a mixture of the compounds of formula (I) wherein R, R.sup.1, R.sup.3, R.sup.4, R.sup.5, R.sup.6 and R.sup.7 are as previously defined and, R.sup.8 is H; however the proportions of the various components can vary depending on the particular organism used, the carboxylic acid employed and the conditions used.
We have found that a broad range of carboxylic acids as defined by R.sup.2 CO.sub.2 H may be added to the fermentation to yield milbemycin derivatives having a novel substituent at the 25-position. Examples of particular acids which may be employed include the following:
In one particular and preferred aspect of the invention the fermentation is performed in the presence of 2-methylthiopropionic acid sodium salt to yield predominantly the compounds of formula (II) wherein R.sup.2 is (1-methylthio)ethyl and R.sup.4 is H.
In another preferred aspect of the invention the fermentation is performed in the presence of 2-methylbutyric acid sodium salt to yield predominantly the compound of formula (II) wherein R.sup.2 is 2-butyl and R.sup.4 is H or methyl.
In a further preferred aspect of the invention the fermentation is performed in the presence of 2-methylpent-4-enoic acid sodium salt to yield predominantly the compound of formula (II) wherein R.sup.2 is 2-pent-4-enyl and R.sup.4 is H.
Compounds of the formula (I) wherein R.sup.8 is H may be converted to the corresponding compounds wherein R.sup.8 is halogen using published procedures. The reaction is performed by first protecting the hydroxyl groups present, at the 5, 6, 8a and 23 positions, for example as the t-butyldimethylsilyloxy acetyl derivative, followed by halogenation at the 13 position using for example N-bromosuccinimide in the presence of light followed by deprotection. Alternatively the process is performed by epoxidation of the 14, 15 double bond using a peracid, for example m-chloroperbenzoic acid. The hydroxyl groups present at the 5, 6, 8a and 23 positions are protected, for example as the t-butyldimethylsilyl derivative, and the compound is treated with a pre-formed complex of hydrazoic acid (HN.sub.3) and triethylaluminium in an inert solvent to give the 15-hydroxy-.DELTA..sup.13,14 -milbemycin derivative. This compound is then converted to the 13-halogeno-milbemycin by treatment with an appropriate halogenating reagent, for example phosphorus tribromide, to give the 13-bromo derivative. These steps together with appropriate reagents and reaction conditions are described in the European patent application No. 0184989.
The halo-compounds, as well as being active anti-parasitic agents, can serve as intermediates for preparation of the corresponding avermectin derivatives. Thus the protected halo-derivative is converted to the 13-acetoxy derivative by treatment with a mixture of sodium acetate in acetic acid. Subsequent reaction with sodium hydroxide gives the 13-hydroxy milbemycin to which the L-oleandrosyl-.alpha.-L-oleandrosyloxy group may be attached by reaction with an acetohalo derivative of the disaccharide. The product is then finally deprotected to give the avermectin. These steps together with appropriate reagents and reaction conditions are described in U.S. Pat. No. 4093629 and British patent No. 1579118. Certain of the avermectin products produced by this procedure are novel compounds, not previously obtainable.
The compounds of formula (I) wherein R and R.sup.1 are taken together and are oxo may be isolated from the mixture of products obtained in the fermentation of the organism Streptomyces thermoarchaensis NCIB 12015 or of a mutant thereof as described in British patent application GB No. 2176182A, or they may be obtained by oxidation of the corresponding compounds of formula (I) wherein R is H and R.sup.1 is OH. Appropriate reagents and procedures for performing the oxidation are described in GB No. 2176182A.
The compounds of formula I wherein R.sup.4 is H may also be prepared from the corresponding compounds wherein R.sup.4 is CH.sub.3 by demethylation. This reaction is achieved by treating the 5-methoxy compound, or a suitably protected derivative thereof, with mercuric acetate and hydrolysing the resulting 3-acetoxy enol ether with dilute acid to give the 5-keto compound. This is then reduced using, for example, sodium borohydride to yield the 5-hydroxy derivative. Appropriate reagents and reaction conditions for these steps are described in U.S. Pat. No. 4423209.
The compounds of the invention are highly active antiparasitic agents having particular utility as anthelmintics, ectoparasiticides, insecticides and acaricides.
Thus the compounds are effective in treating a variety of conditions caused by endoparasites including, in particular, helminthiasis which is most frequently caused by a group of parasitic worms described as nematodes and which can cause severe economic losses in swine, sheep, horses and cattle as well as affecting domestic animals and poultry. The compounds are also effective against other nematodes which affect various species of animals including, for example, Dirofilaria in dogs and various parasites which can infect humans including gastro-intestinal parasites such as Ancylostoma, Necator, Ascaris, Strongyloides, Trichinella, Capillaria, Trichuris, Enterobius and parasites which are found in the blood or other tissues and organs such as filiarial worms and the extra intestinal stages of Strongyloides and Trichinella.
The compounds are also of value in treating ectoparasite infections including in particular arthropod ectoparasites of animals and birds such as ticks, mites, lice, fleas, blowfly, biting insects and migrating dipterous larvae which can affect cattle and horses.
The compounds are also insecticides active against household pests such as the cockroach, clothes moth, carpet beetle and the housefly as well as being useful against insect pests of stored grain and of agricultural plants such as spider mites, aphids, caterpillars, fire ants, termites and against migratory orthopterans such as locusts.
The compounds of formula (I) are administered as a formulation appropriate to the specific use envisaged and to the particular species of host animal being treated and the parasite, or insect involved. For use as an anthelmintic the compounds may be administered orally in the form of a capsule, bolus, tablet or preferably a liquid drench, or alternatively, they may be administered by injection or as an implant. Such formulations are prepared in a conventional manner in accordance with standard veterinary practice. Thus capsules, boluses or tablets may be prepared by mixing the active ingredient with a suitable finely divided diluent or carrier additionally containing a disintegrating agent and/or binder such as starch, lactose, talc, magnesium stearate etc. A drench formulation may be prepared by dispersing the active ingredient in an aqueous solution together with dispersing or wetting agents etc. and injectable formulations may be prepared in the form of a sterile solution which may contain other substances, for example, enough salts or glucose to make the solution isotonic with blood. These formulations will vary with regard to the weight of active compound depending on the species of host animal to be treated, the severity and type of infection and the body weight of the host. Generally for oral administration a dose of from about 0.001 to 10 mg per Kg of animal body weight given as a single dose or in divided doses for a period of from 1 to 5 days will be satisfactory but of course there can be instances where higher or lower dosage ranges are indicated and such are within the scope of this invention.
As an alternative the compounds may be administered with the animal feedstuff and for this purpose a concentrated feed additive or premix may be prepared for mixing with the normal animal feed.
For use as an insecticide and for treating agricultural pests the compounds are applied as sprays, dusts, emulsions and the like in accordance with standard agricultural practice.
For human use the compounds are administered as a pharmaceutically acceptable formulation in accordance with standard medical practice.
US Referenced Citations (1)
| Number |
Name |
Date |
Kind |
|
4696922 |
Sturm et al. |
Sep 1987 |
|
Foreign Referenced Citations (6)
| Number |
Date |
Country |
| 0170006 |
Jun 1986 |
EPX |
| 0214731 |
Mar 1987 |
EPX |
| 300674 |
Jan 1989 |
EPX |
| 2166436 |
May 1986 |
GBX |
| 2167751 |
Jun 1986 |
GBX |
| 2176182 |
Dec 1986 |
GBX |
Divisions (1)
|
Number |
Date |
Country |
| Parent |
227921 |
Aug 1988 |
|
Patent Grant
4929638
