ANTIPARASITIC AGENTS

Abstract: An antiparasitic compound of formula (I), (II) or (III) wherein R is selected from a variety of organic groups, the broken line represents an optional double bond, R<1> is H, OH, -O-alkyl or optionally substituted oximino, and R<2> and R<3> are H, OH, H, OMe, oxo, optionally substituted oximino or optionally substituted amino.

Description: Antiparasitic Agents This invention relates to antiparasitic agents and in particular to compounds related to the avermectins but in which the oxygen atom bonded to the 6,8a positions of the avermectin nucleus is missing, that is the compounds are 6.8a-seco deoxyavermeqtin derivatives. The invention also relates to methods of making these compounds and to compositions containing them. The avermectins are a group of broad spectrum antiparasitic agents referred to previously as the C-076 compounds. They are produced by fermenting a strain of the micro-organism Streptomvces avermitilis under aerobic conditions in an aqueous nutrient medium containing inorganic salts and assimilable sources of carbon and nitrogen. The isolation and the chemical structure of the eight individual components which make up the C- 076 complex is described in detail in British Patent Specification 1573955. In our European Patent Applications 0214731, 0284176, 0317148, 0308145, 0340832, 0335541 and 0350187 there are described preparations of compounds related to the avermectins but having a group at the 25- position other than the isopropyl or sec-butyl groups found in the original avermectin compounds disclosed in British Patent Specification 1573955. Such compounds may be prepared by fermentation of particular strains of Streptomyces avermitilis in the presence of organic acids or derivatives thereof. It has now been discovered that certain mutants of these strains are capable of producing during fermentation compounds related to the avermectins but in which the oxygen atom bonded to the 6,8a positions of the avermectin nucleus is absent, i.e. they are 6,8a-seco-deoxyavermectins. The present invention relates to these compounds and to certain derivatives which may be made from them. According to one aspect of the invention, there are provided compounds of formula (I), (II) or (III): (D OD (ΠD wherein R is:- (a) an alpha-branched C 3 -C 8 alkyl, alkenyl, alkoxyalkyl, or alkylthioalkyl group; an alpha-branched C 4 -C 8 alkynyl group; a (C 3 -C 8 cycloalkyl)alkyl group wherein the alkyl group is. an alpha-branched C 2 -C 5 alkyl group; a C 3 -C 8 cycloalkyl or C 5 -C 8 cycloalkenyl group, either of which may optionally be substituted by methylene or one or more C,-C 4 alkyl groups or halo atoms; 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,-C 4 alkyl groups or halo atoms; or (b) a group of the formula -CH 2 R 4 wherein R 4 is H, alkyl, C 2. C 8 alkenyl, C 2 -C 8 alkynyl, alkoxyalkyl or alkylthioalkyl containing from 1 to 6 carbon atoms in each alkyl or alkoxy group, wherein any of said alkyl, alkoxy, alkenyl or alkynyl groups may be substituted by one or more halo atoms; or a C 3 -C 8 cycloalkyl or C 5 -C β cycloalkenyl group, either of which may optionally be substituted by methylene or one or more C,-C 4 alkyl groups or halo atoms; 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 alkyl groups or halo atoms; or a group of the formula SR 5 wherein R 5 is alkyl, C 3 -C 8 alkenyl, C 3 -C 8 alkoxyalkyl, C 2 -C 8 alkynyl, C 3 -C 8 cycloalkyl, C 5 -C 8 cycloalkenyl, phenyl or substituted phenyl wherein the substituent is C C 4 alkyl, C,-C 4 alkoxy or halo; 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^C,, alkyl groups or halo atoms; or (c) a C,-C 6 alkyl group substituted by one oxo or one or more hydroxy groups or by a single oxygen atom on two adjacent carbon atoms forming an oxirane ring, or R is a alkyl group substituted by a alkoxycarbonyl group, said substituents on R being attached to either or both of a terminal carbon atom and a carbon atom adjacent to a terminal carbon atom of R; or (d) =CH 2 or a group of the formula: R 6 I -(X)-C=CHR 7 wherein R 6 and R 7 are both H; R 6 is H and R 7 is C C 3 alkyl, or one of R 6 and R 7 is H and the other is phenyl, heteroaryl, C 2 -C 6 alkoxycarbonyl or substituted phenyl or heteroaryl wherein said substituent is halo, C C 4 alkyl, C C 4 alkoxy, C,-C 4 alkylthio, hydroxy(C C 4 )alkyl, cyano, aminosulphonyl, C 2 -C 6 alkanoyl, C 2 - C 6 alkoxycarbonyl, nitro, trifluoromethyl, trifluoromethoxy, amino or mono or di-fC,^ alkyl)amino; and X is a direct bond or is an alkylene group having from 2 to 6 carbon atoms which may be straight or branched-chain; or (e) phenyl which may optionally be substituted with at least one substituent selected from C C 4 alkyl, ^^ alkoxy and C,-C 4 alkylthio groups, halo atoms, trifluoromethyl, and cyano; (f) or R may be a group of the formula below: wherein Z is O, S or -CH 2 - and a, b, c and d may each independently be 0, 1 or 2; the sum of a, b, c and d not exceeding 5; the broken line at the 22-23 position represents an optional double bond, wherein R 1 is H, OH, alkyl), oxo or optionally substituted oximino when the double bond is absent, or, the double bond is present and R 1 is absent;and R 2 and R 3 are independently H and OH, H and 0,-Cg alkoxy or H and C,- C 6 acyloxy, these radicals being attached to the remainder of the molecule by single bonds, or are oxo or optionally O - substituted oximino attached by a double bond, or in formula (I) or (II) R 2 is as defined above and R 3 is H, amino wherein said amino is optionally substituted with a C^C,, alkyl, aralkyl or acyl group or a C 3 -C 8 alkenyl, or alkynyl group, with the proviso that when R 2 is H and OH, H and methoxy or oxo and R 3 is H and OH, in formula (I), (II) or (III) then R is not isopropyl or sec-butyl. In the above definitions "halo" means F, Cl, Br or I. U.S. Patent 4378353 mentions certain 6,8a-sjgsQ-deoxyavermectins which are made by fermentation using a mutant culture deposited under no. ATCC 31780. These compounds are of the formulae (IV), (V) and (VI): OR, (IV) wherein (a) R., is α-L-oleandrosyl; R 2 is sec-butyl; and R 3 is methyl; (b) R, is α-L-oleandrosyl; R 2 is sec-butyl; and R 3 is hydrogen; (c) R 1 is α-L-oleandrosyl-α-L-oleandrosyl; R 2 is sec-butyl and R 3 is hydrogen. (V) wherein (a) R 2 is iso-propyl; and R 3 is methoxy; (b) R 2 is sec-butyl; and R 3 is keto; (c) R 2 is iso-propyl; and R 3 is keto; and (VI) wherein R., is α-L-oleandrosyl-α-L-oleandrosyl; R 2 is sec-butyl; and R 3 is hydrogen. U.S. Patent 4285963 mentions seco-avermectins produced by fermentation using the micro-organisms which produced the originally- discovered C-076 compounds. These compounds are of the formulae (VII) and (VIII): (vπ) wherein (a) R*> is OH and R 2 is sec-butyl; (b) R, is =0 and R 2 is sec-butyl; (c) R is -OH and R 2 is iso-propyl; and ( ffl) wherein R 3 is (a) hydrogen and (b) hydroxyl. The R group of the 25- position in compounds (I), (II) and (III) is preferably a straight or branched-chain C^C,, alkyl, alkenyl or cycloalkyl group or a 5 or 6- membered oxygen- or sulphur- containing heterocyclic group. R is most preferably a cyclohexyl, cyclobutyl or 3 - thienyl group. In preferred compounds either the optional bond is present at the 22-23 position, or this optional bond is absent and R 1 is H or OH or oxo or oximino. R 2 is preferably H, OH or oxo or oximino. R 3 is preferably H, OH or H, NHR 8 where R 8 is H, C -Q β alkyl or acyl. The C-076 compounds comprise eight distinct but closely related compounds described as C-076 A1a, A1b, A2a, A2b, B1a, B1b, B2a and B2b. The "a" series of C-076 compounds have an (S)-sec-butyl constituent at the 25-position of the avermectin nucleus and the "b" series have an isopropyl group at this position. The designations "A" and "B" refer to avermectins wherein the 5-substituent is methoxy or hydroxy, respectively, numeral "1" refers to avermectins in which a double bond is present at the 22-23 position and numeral "2" to avermectins lacking the 22-23 double bond and having a hydrogen at the 22-position and hydroxy at the 23- position. In this specification the "a" and "b" identifiers have been dropped but the identifiers A1 , A2, B1 and B2 have been retained to refer to seco- deoxyavermectins having the structural features corresponding to those of the original C-076 avermectins mentioned above. Some of the compounds of the invention may be made by fermenting the strain of the micro-organism deposited at the American Type Culture Collection, 12301 Parklawn Drive, Rockville, Maryland 20852, USA under accession number ATCC 55372. This micro-organism is a Streptomyces avermitilis strain related to known Streptomyces avermitilis strain ATCC 31272, of which the morphological and cultural properties are described in British Patent Specification 1573955. The properties of ATCC 31272 and ATCC 55372 are compared and contrasted in following Tables 1 , 2 and 3. Regarding antimicrobial activity, ATCC 31272 shows antibiosis against Streptomyces murinus 19788 and Aspergillus niαer 16404, whereas ATCC 55372 does not. TABLE 1 Isolate : Streotomvces avermtilis ATCC 31272 Morphology and pigmentation of conidial chains and condiophores after 14 days: Melanin production on ISP-6: positive Growth at 50°C negative Melanin production on tyrosine agar: positive Table 1 continued Carbon utilization: Control no growth Arabinose good growth D-fructose no growth Glucose good growth l-inositol good growth D-mannitol good growth ISP-2 = Yeast extract-malt extract agar ISP-5 = Glycerol asparagine agar ISP-3 = Oatmeal agar ISP-6 = Peptone-Yeast Extract - Iron agar ISP-4 = Inorganic starch agar I TABLE 2 Isolate : Streptomyces avermitilis ATCC 55372 Morphology and pigmentation of conidial chains and condiophores after 14 days: Melanin production on ISP-6: negative Growth at 50°C negative Melanin production on tyrosine agar: negative Table 2 (continued) (Thiamine added) no growth no growth moderate growth moderate growth moderate growth moderate growth no growth moderate growth no growth moderate growth no growth moderate growth 4 I ISP-2 = Yeast extract-malt extract agar ISP-5 = Glycerol asparagine agar ISP-3 = Oatmeal agar ISP-6 = Peptone-Yeast Extract - Iron agar ISP-4 = Inorganic starch agar Table 3 Physiological Comparison of Streptomyces avermitilis ATCC 31272 and strain ATCC 55372 The fermentation should be conducted under aerobic conditions in an aqueous nutrient medium containing inorganic salts and assimilable sources of carbon and nitrogen. In the absence of an added carboxylic acid or suitable precursor no compounds of the invention are produced by the fermentation; compounds in which R is one of the groups identified above are obtained when a carboxylic acid of formula R-C0 2 H or a salt, ester or amide thereof is added to the fermentation medium. The fermentation and isolation of the seco-deoxyavermectins obtained may be carried out as described in European Patent Application 0214731 et seq. mentioned above. The compounds of the invention or the compounds convertible thereto obtained by fermentation in this way are: (i) compounds of formula I, that is the sgcσ-deoxyavermectin disaccharide, in which R 2 and R 3 are H, OH and either the double bond at the 22-23 position is present and R 1 is absent, or the double bond is absent and R 1 is OH, and (ii) the monosaccharide compounds of formula II in which R 3 is H, OH, R 2 is either H, -OH or =0 and either the double bond at the 22-23 position is present and R 1 is absent, or the double bond is absent and R 1 is OH. Other compounds of the invention may be made by synthesis starting from these fermentation - derived seco-deoxyavermectins. The synthetic steps required to provide the desired compounds may require sequential reactions at different positions around the seso-deoxyavermectin nucleus and the exact order of these operations may vary. In practice certain functionalities in the molecule may be incompatible with the reaction conditions used and a protecting group is then required to avoid undesirable side reactions. A preferred protecting group for exposed hydroxy groups is tertbutyldimethylsilyl (TBDMS). Some of chemistry involved in these synthetic transformations is reviewed in Macrolide Antibiotics, Omura Sp., Ed., Academic Press, New York (1984) and by Davies, H.G. and Green, R.H. in Natural Product Reports (1986), 3_, 87-121 ; Chemical Society Reviews (1991), 20, 211-269 and 271-339. The disaccharide compounds may also generally be converted to the corresponding monosaccharide compounds, and the monosaccharides to the aglycones, by hydrolysis with dilute sulphuric acid in the presence of a solvent such as isopropyl alcohol. The R 2 group may be converted from H, OH to H, OCH 3 , when desired, by reaction with a methyl halide, preferably the iodide, in the presence of silver salts, preferably the oxide, by a method analagous to that described in United States patent 4,200,581. The R 2 group may be converted from H, -OH to oxo, when desired, by reaction with manganese dioxide. The R 1 and R 3 group may be converted from H, OH to oxo, when desired, by reaction with a suitable oxidizing agent for example using the Swern procedure as described in United States patent 4427663. The corresponding oximino derivatives may be formed by reaction of the oxo compound with O- substituted or unsubstituted hydroxylamine, followed by O-acylation or alkylation if necessary. The R 3 group may be converted from oxo to H, amino, when desired, by reductive amination according to the procedure described in United States patent 4,427,663. Compounds in which R 1 is an alkoxy group may be prepared from the corresponding compound in which R 1 is OH by reaction with an appropriate alkyl bromide or iodide in the presence of a silver salt such as silver salicylate ' , as described in our copending British patent application no. 92/01505. When desired, the compounds of the invention having a double bond at the 22-23 position may be converted to the corresponding compounds having a single bond by hydrogenation in the presence of a suitable catalyst such as Wilkinson's catalyst as described in United States patent 4199569. The compounds of the invention 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 livestock, companion animals such as cats and dogs and also humans including gastro-intestinal parasites such as Ancylostoma. Necator. Ascaris. Strongyloides. Trichinella, Capillaria. Toxocara. Toxascaris. Trichuris. Enterobius and parasites which are found in the blood or other tissues and organs such as filarial worms and the extra intestinal stages of Strongyloides. Toxocara and Trichinella. The compounds are also of particular value in treating ectoparasite infections including arthropod ectoparasites of animal 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 arthropod pests of stored grain and of agricultural plants such as spider mites, aphids, caterpillars and against migratory orthopterans such as locusts. Unexpectedly we have discovered that compounds within the scope of this invention have highly potent activity against important arthropod parasites. The compounds of formula (I), (II) or (III) may be 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 by injection, either subcutaneously or intramuscularly, alternatively they may be administered orally in the form of a capsule, bolus, tablet, chewable tablet or liquid drench, or they may be administered as a pour-on or spot-on formulation 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, or magnesium stearate. A drench formulation may be prepared by dispersing the active ingredient in an aqueous solution together with dispersing or wetting agents and injectable formulations may be prepared in the form of a sterile solution or emulsion. Pour-on or spot-on formulations may be prepared by dissolving the active ingredient in an acceptable liquid carrier vehicle, such as butyl digol, liquid paraffin or non-volatile ester with or without addition of a volatile component such as isopropanol. 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, parenteral and pour-on administration a dose of from about 0.001 to 10mg 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, pour-on or spot-on formulations, 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 normal medical practice. The preparation of compounds according to the invention are illustrated by the following Examples. Example 1 A frozen inoculum (2ml) of a culture of Streptomyces avermitilis mutant strain ATCC 55372 was inoculated into 50ml of a medium containing starch (1g), Pharmamedia (Trademark) (0.75g), Ardamine pH (Trademark) (0.25g) and calcium carbonate (0.1g) in a 300ml flask and incubated at 28°C for 2 days. This inoculum (50ml) was transferred to a second inoculum flask (1 litre) containing starch (20g), Pharmamedia (15g), Ardamine pH (5g) and calcium carbonate (2g) and incubated at 28°C for a further 2 days. This inoculum was added to 100 litres of a medium containing starch (8kg), Oxoid (Trademark) yeast extract (500g), magnesium sulphate heptahydrate (100g), dipotassium hydrogen phosphate (100g), monosodium glutamate (100g), zinc sulphate (0.1 g), manganese (II) chloride (0.1g), iron (II) sulphate (10g) and calcium carbonate (700g) contained in a 150 litre fermenter and with a natural pH of 7.05. The fermentation was incubated at 29°C with agitation at 200 rpm and with aeration at 40 litres per minute. Cyclohexanecarboxylic acid sodium salt (200g) was added to the fermentation after 24 hours. After 14 days the broth was harvested by ethyl acetate extraction and the organic layer was filtered and concentrated to an oil (62g) which was then chromatographed on 1 kg silica (Merck kieselgel 60) eluting initially with dichloromethane then dichloromethane containing a progressively higher proportion of ethyl acetate. The desired compounds began to elute when the mobile phase was 4:1 dichloromethane:ethyl acetate. These were recognised by their characteristic high performance liquid chromatography retention times and ultraviolet spectra, as captured by a diode array detector, as shown in the Table 4 below. Table 4 Retention Compound Seco-6,8a-deoxy-25-cyclohexyl- avermectin B1 Seco-6,8a-deoxy-25-cyclohexyl- avermectin B2 Seco-6,8a-deoxy-25-cyclohexyl- avermectin B1 monosaccharide Seco-6,8a-deoxy-25-cyclohexyl- avermectin B2 monosaccharide 5-Keto-seco-6,8a-deoxy-25-cyclohexyl- avermectin B1 monosaccharide 5-Keto-seco-6,8a-deoxy-25-cyclohexyl- avermectin B2 monosaccharide * Beckman Ultrasphere ODS (Trademark) 5μm, 4.6x250mm, eluting with a methanol- water gradient of 80:20 linearly to 95:5 over 40 min at 0.85ml per minute and 40°C. Final purification of the desired compounds was achieved by a combination of reverse phase high performance liquid chromatography and normal phase (silica) column chromatography. The NMR spectra obtained were as follows. Seco-6.8a-deoxy-25-cyclohexylavermectin B1. NMR (CDCI 3 ) (in part): δ = 6.3(d), 6.05(dd), 5.75(dd), 5.65(dd), 5.55(dd), 3.5(s), 3.45(s), 3.3(t), 3.2(t), 1.85(bs), 1.75(bs). Seco-6.8a-deoxy-25-cyclohexylavermectin B2. NMR (CDCI 3 ) (in part): δ = 6.3(d), 6.05(dd), 5.65(dd), 3.5(s), 3.45(s), 3.25(t), 3.20(t), 1.9(bs), 1.75(bs). Seco-6.8a-deoxy-25-cyclohexylavermectin B1 monosaccharide. NMR (CDCI 3 ) (in part): δ = 6.3(d), 6.0(dd), 5.75(dd), 5.6(dd), 5.55(dd), 3.5(s), 3.15(t), 1.85(bs), 1.70(bs). Seco-6.8a-deoxy-25-cyclohexylavermectin B2 monosaccharide. NMR (CDCI 3 ) (in part): δ = 6.25(d), 6.0(dd), 5.6(dd), 5.3(m), 3.5(s), 3.15(t), 1.85(bs) 1.70(bs). 5-Keto-seco-6.8a-deoxy-25-cyclohexylavermectin B1 monosaccharide. NMR (CDCI 3 ) (in part): δ = 6.42(bs), 6.3(d), 6.0(dd), 5.75(dd), 5.6(dd), 5.55(dd), 3.5(s), 3.15(t), 2.8(dd), 1.85(bs), 1.75(bs). 5-Keto-seco-6.8a-deoxy-25-cyclohexylavermectin B2 monosaccharide. NMR (CDCI 3 ) (in part): δ = 6.45(bs), 6.3(d), 6.0(dd), 5.6(dd), 5.35(m), 3.5(s), 3.15(t), 2.8(dd), 1.85(bs), 1.75(bs). Example 2 Seco-6.8a-deoxy-25-cyclohexylavermectin B2 monosaccharide Seco-6,8a-deoxy-25-cyclohexylavermectin B2 (1.0g) (Example 1) was dissolved in isopropanol (10ml) and a solution of sulphuric acid (0.2ml) in isopropanol (10ml) was added. The solution was stirred at room temperature for 20 hours then poured into water, extracted with methylene chloride and the layers separated. The organic layer was dried over anhydrous sodium sulphate and evaporated to dryness. The crude product was chromatographed on 8μm SiO 2 -ODS (40.1 x 250mm, Dynamax, Trademark-Rainin) eluting with methanol-water 4:1 at 69ml per minute to give the title compound (618mg) identical to material isolated from the fermentation of Example 1 and Seco-6.8a-deoxy-25-cyclohexylavermectin B2 aglycone (33mg). NMR (CDCI 3 ) (in part) δ = 6.25(d), 6.05(dd), 5.55(dd), 5.3(m), 5.15(m), 4.45(m), 3.95(bs), 3.55(d), 3.35(d), 1.85(bs), 1.70(bs), 1.60(bs), 0.9(d), 0.75(g). Example 3 Seco-6.8a-deoxy-22.23-dihydro-25-cyclohexylavermectin B1 Seco-6,8a-deoxy-25-cyclohexylavermectin B1 (1.3g) (Example 1) was dissolved in degassed toluene (200ml) and tris(triphenylphosphine)rhodium (I) chloride (100mg) was added. After a brief period of sonication the solution was shaken under a hydrogen atmosphere (35-70KPa) at room temperature. After 48 hours a further 100mg of catalyst was added, the hydrogen pressure raised to 280KPa and the temperature raised to 35°C. After 20 hours the solution was filtered through silica, washed through with methanol and the combined solutions evaporated to dryness. The title compound was finally purified by reverse phase hplc eluting with methanol- water 95:5. Both NMR and mass spectroscopic data were fully consistent with the proposed structure. Example 4 Seco-6.8a-deoxy-22.23-dihydro-25-cyclohexylavermectin B1 monosaccharide The title compound was prepared from the product of Example 3 by a method exactly similar to that described in Example 2. NMR and mass spectroscopic data were fully consistent with the proposed structure. Example 5 5-Oximino-seco-6.8a-deoxy-22.23-dihydro-25-cyclohexylavermectin B1 6,8a-Deoxy-22,23-dihydro-25-cyclohexylavermectin B1 (50mg) (Example 3) was dissolved in ether (50ml) and manganese (IV) oxide (100mg) was added. The suspension was stirred at room temperature, filtered and evaporated to dryness to give 5-keto-6,8a-deoxy-22,23-dihydro- 25-cyclohexyiavermectin B1 as a white solid (40mg). This was dissolved in pyridine (2ml) and hydroxylamine hydrochloride (50mg) was added. The mixture was stirred at room temperature for 24 hours then poured into dilute hydrochloric acid, extracted with methylene chloride and the organic layer was dried over anhydrous sodium sulphate and evaporated to dryness. The residue was purified by reverse phase hplc eluting with methanol-water 95:5 to give the pure title compound (28mg) as a white solid. NMR and mass spectroscopic data were fully consistent with the proposed structure. Example 6 5-Oximino-seco-6.8a-deoxy-22.23-dihydro-25-cyclohexylavermectin B1 monosaccharide 6,8a-Deoxy-22,23-dihydro-25-cyclohexylavermectin B1 monosaccharide (Example 4) was converted to the title compound by a method exactly similar to that described in Example 5. NMR and mass spectroscopic data were fully consistent with the proposed structure. Example 7 5-Oximino-seco-6.8a-deoxy-25-cyclohexylavermectin B1 monosaccharide 5-Keto-seco-6,8a-deoxy-25-cyclohexylavermectin B1 monosaccharide (77mg) (Example 1) was dissolved in pyridine (2ml) and hydroxylamine hydrochloride (100mg) was added. The mixture was stirred overnight at room temperature for 18 hours then poured into an ice/water mixture, acidified by adding dilute sulphuric acid (2N) and extracted with methylene chloride. The organic extract was dried over anhydrous sodium sulphate and evaporated to dryness under reduced pressure. The residue was purified by reverse phase HPLC on a Dynamax column (24mm x 250cm, 5μm, ODS- silica, Rainin) eluting with methanol - water 90:10 at 9ml per minute. Fractions eluting between 17 and 23 minutes were combined and evaporated to dryness under vacuum to yield the title compound as a white powder (58mg). Mass and NMR spectroscopic data were fully consistent with the proposed structure. Example 8 5-Oximino-seco-6.8a-deoxy-25-cyclohexylavermectin B2 monosaccharide 5-Keto-seco-6,8a-deoxy-25-cyclohexylavermectin B2 monosaccharide (280mg) (Example 1) was treated with hydroxylamine hydrochloride (300mg) in pyridine (10ml) according to the method described in Example 7. Final purification was achieved using preparative reverse phase HPLC on a Dynamax column (24mm x 250cm, 5μm, ODS-silica, Rainin) eluting with methanol - water 85:15 at 9ml per minute. Appropriate fractions were combined and evaporated to dryness under vacuum to yield the title compound as a white powder (192mg). Mass and NMR spectroscopic data were fully consistent with the proposed structure. Example 9 Seco-6.8a-deoxy-25-cyclobutylavermectins were produced by adding cyclobutane carboxylic acid to a fermentation of the Streptomyces avermitilis mutant strain ATCC 55372 in. a manner as described in Example 1 except that 10g of cyclobutane carboxylic acid was added after 43 hours and again after 68 hours and the whole fermentation harvested after 7 days. The desired compounds were recognised by their characteristic HPLC retention times and UV spectra, as captured by a diode array detector, as shown in Table 5 below. Table 5 Compound Retention UV. Time (min) * max -torn) Seco-6,8a-deoxy-25-cyclobutylavermectin B1 22.7 242 Seco-6,8a-deoxy-25-cyclobutylavermectin B2 13.5 242 Seco-6,8a-deoxy-25-cyclobutylavermectin B1 monosaccharide Seco-6,8a-deoxy-25-cyclobutylavermectin B2 monosaccharide 5-Keto-seco-6,8a-deoxy- . 25- cyclobutylavermectin B2 monosaccharide * Beckman Ultrasphere ODS (trademark) 5μm, 4.6x250mm, eluting with a methanol-water gradient of 80:20 linearly to 95:5 over 40 minutes at 0.85ml per minute and 40°C. Final purification of the desired compounds was achieved by a combination of reverse phase HPLC and normal phase (silica) column chromatography. The NMR and mass spectroscopic data were fully consistent with the proposed structures. Example 10 Seco-6.8a-deoxy-25-cyclobutylavermectin B2 monosaccharide Seco-6,8a-deoxy-25-cyclobutylavermectin B2 (0.5g) (Example 9) was dissolved in isopropyl alcohol (10ml) containing 1% sulphuric acid v/v. The solution was allowed to stand for 24 hours then poured into an ice/water mixture and extracted with methylene chloride (2x 50ml). The combined extracts were washed with a 5% w/v sodium bicarbonate solution, dried over anhydrous sodium sulphate and evaporated to dryness under reduced pressure to yield a crude product. Final purification was achieved using preparative reverse phase HPLC on a Dynamax column (24mm x 250cm, 5m, ODS-silica, Rainin) eluting with methanol - water 85:15 at 9ml per minute. Appropriate fractions were combined and evaporated to dryness under vacuum to yield the title compound as a white powder. Mass and NMR spectroscopic data were fully consistent with the proposed structure. Example 11 Seco-6.8a-deoxy-22.23-dihvdro-25-cyclobutylavermectin B1 Seco-6,8a-deoxy-25-cyclobutylavermectin B1 (0.8g) (Example 9) was dissolved in degassed toluene (200ml) and tris(triphenyl)phosphine) rhodium (I) chloride (1g) added. After a brief period of sonication hydrogen gas was slowly bubbled through the solution. After 20. hours the reaction mixture was filtered through silica, washed with methanol and the combined eluates evaporated to dryness to give a crude product which was further purified using preparative reverse phase HPLC on a Dynamax column (24mm x 250cm, 5μm, ODS-silica, Rainin) eluting with methanol - water 95:5 at 27ml per minute. Appropriate fractions were combined and evaporated to dryness under vacuum to yield the title compound as a white powder. Mass and NMR spectroscopic data were fully consistent with the proposed structure. Example 12 Seco-6.8a-deoxy-22.23-dihydro-25-cyclobutylavermectin B1 monosaccharide Seco-6,8a-deoxy-22,23-dihydro-25-cyclobutylavermectin B1 (0.48g) (Example 11) was dissolved in isopropyl alcohol (10ml) containing 1% sulphuric acid v/v. The desired product was recovered and purified using the method described in Example 10 except that the HPLC eluate used was methanol - water 90:10. Appropriate fractions were combined and evaporated to dryness under vacuum to yield the title compound as a white powder (266mg). Mass and NMR spectroscopic data were fully consistent with the proposed structure. Example 13 Seco-6.8a-deoxy-25-(3-thienyl)avermectins were produced by adding thiophene-3-carboxylic acid to a fermentation of the Streptomyces avermitilis mutant strain ATCC 55372 in a manner as described in Example 1 except that 10g thiophene-3-carboxylic acid was added after 43 hours and again after 68 hours and the whole fermentation harvested after 7 days. The desired compounds were recognised by their characteristic HPLC retention times and UV spectra, as captured by a diode array detector, as shown in Table 6 below. Table 6 Compound Seco-6,8a-deoxy-25-(3-thienyl)avermectin B1 Seco-6,8a-deoxy-25-(3-thienyl)avermectin B2 Seco-6,8a-deoxy-25-(3-thienyl)avermectin B1 monosaccharide Seco-6,8a-deoxy-25-(3-thienyl)avermectin B2 7.0 240 monosaccharide * Beckman Ultrasphere ODS (trademark) 5μm, 4.6x250mm, eluting with a methanol-water gradient of 80:20 linearly to 95:5 over 40 minutes at 0.85ml per minute and 40°C. Final purification of the desired compounds was achieved by a combination of reverse phase HPLC and normal phase (silica) column chromatography. The NMR and mass spectroscopic data were fully consistent with the proposed structures. Example 14 Seco-6.8a-deoxy-25-(3-thienyl)avermectin B2 monosaccharide Seco-6,8a-deoxy-25-(3-thienyl)avermectin B2 (0.3g) (Example 13) was dissolved in isopropyl alcohol (15ml) containing 1% sulphuric acid v/v. The desired product was recovered and purified using the method described in Example 10 except that the HPLC eluate used was methanol - water 80:20. Appropriate fractions were combined and evaporated to dryness under vacuum to yield the title compound as a white powder (180mg). Mass and NMR spectroscopic data were fully consistent with the proposed structure. Example 15 5-Oximino-seco-6.8a-deoxy-25-(3-thienyl)avermectin B2 monosaccharide Seco-6,8a-deoxy-25-{3-thienyl)avermectin B2 monosaccharide (115mg) (Example 14) was oxidised with manganese (iv) oxide (0.2g) in diethyl ether (100ml) using the method described in Example 5 to give 5-keto-seco--6,8a- deoxy-25-(3-thienyl)avermectin B2 monosaccharide (90mg). This material was further reacted with hydroxylamine hydrochloride (100mg) in pyridine (4ml) again using the method described in Example 5 to yield the title compound as a white powder (75mg). Mass and NMR spectroscopic data were fully consistent, with the proposed structure. Example 16 Seco-6.8a-deoxy-22.23-dihydro-25-(3-thienyπavermectin B1 Seco-6,8a-deoxy-25-(3-thienyl)avermectin B1 (50mg) (Example 13) was hydrogenated using tris(triphenyl)phosphine) rhodium (I) chloride (50mg) in degassed toluene (25ml) using the procedures described in Example 11 except that the final preparative HPLC purification used an eluate consisting of methanol - water 90:10. The title compound was obtained as a white powder (25mg). Mass and NMR spectroscopic data were fully consistent with the proposed structure. Example 17 Seco-6.8a-deoxy-22.23-dihydro-25-(3-thienyhavermectin B1 monosaccharide Seco-6,8a-deoxy-22,23-dihydro-25-(3-thienyl)avermectin B1 (17.5mg) (Example 16) was dissolved in isopropyl alcohol (0.5ml) containing 1% sulphuric acid v/v. The desired product was recovered and purified using the method described in Example 10 except that the final purification was achieved using preparative reverse phase HPLC on a Dynamax column (12mm x 250cm, 5μm, ODS-silica, Rainin) eluting with methanol - water 90:10 at 4ml per minute. Appropriate fractions were combined and evaporated to dryness under vacuum to yield the title compound as a white powder (7.5mg). Mass and NMR spectroscopic data were fully consistent with the proposed structure.

Claims: CLAIMS 1. A compound of formula (I), (II) or (III): (D (π) (ΠD wherein R is:- (a) an alpha-branched C 3 -C 8 alkyl, alkenyl, alkoxyalkyl, or alkylthioalkyl group; an alpha-branched C 4 -C 8 alkynyl group; a (C 5 -C 8 cycloalkyl)alkyl group wherein the alkyl group is an alpha-branched C 2 -C 3 alkyl group; a C 3 -C 8 cycloalkyl or C 5 -C 8 cycloalkenyl group, either of which may optionally be substituted by methylene or one or more C,-C 4 alkyl groups or halo atoms; 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^C,, alkyl groups or halo atoms; or (b) a group of the formula -CH 2 R 4 wherein R 4 is H, alkyl, C 2 - C 8 alkenyl, C 2 -C 8 alkynyl, alkoxyalkyl or alkylthioalkyl containing from 1 to 6 carbon atoms in each alkyl or alkoxy group, wherein any of said alkyl, alkoxy, alkenyl or alkynyl groups may be substituted by one or more halo atoms; or a C 3 -C 8 cycloalkyl or C 5 -C 8 cycloalkenyl group, either' of which may optionally be substituted by methylene or one or more C_,-C 4 alkyl groups or halo atoms; 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^ , alkyl groups or halo atoms; or a group of the formula SR 5 wherein R 5 is alkyl, C 3 -C 8 alkenyl, C 3 -C 8 alkoxyalkyl, C 2 -C β alkynyl, C 3 -C β cycloalkyl, C 3 -C 8 cycloalkenyl, phenyl or substituted phenyl wherein the substituent is C,-C 4 alkyl, C,-C 4 alkoxy or halo; 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 C 4 alkyl groups or halo atoms; or (c) a alkyl group substituted by one oxo or one or more hydroxy groups or by a single oxygen atom on two adjacent carbon atoms forming an oxirane ring, or R is a 0,-Cg alkyl group substituted by a (G,-C 6 alkoxycarbonyl group, said substituents on R being attached to either or both of a terminal carbon atom and a carbon atom adjacent to a terminal carbon atom of R; or (d) =CH 2 or a group of the formula: R 6 I -(X)-C=CHR 7 wherein R 6 and R 7 are both H; R 6 is H and R 7 is 0,-0, alkyl, or one of R 6 and R 7 is H and the other is phenyl, heteroaryl, C 2 -C 6 alkoxycarbonyl or substituted phenyl or heteroaryl wherein said substituent is halo, C C 4 alkyl, C,-C 4 alkoxy, C,-C 4 alkylthio, hydroxy(C,-C 4 )alkyl, cyano, aminosulphonyl, C 2 -C 6 alkanoyl, C 2 - C 6 alkoxycarbonyl, nitro, trifluoromethyl, trifluoromethoxy, amino or mono or di-(C_,-C 4 alkyl)amino; and X is a direct bond or is an alkylene group having from 2 to 6 carbon atoms which may be straight or branched-chain; or (e) phenyl which may optionally be substituted with at least one substituent selected from C,-C 4 alkyl, 0,-0 4 alkoxy and 0,-0, alkylthio groups, halo atoms, trifluoromethyl, and cyano; (f) or R may be a group of the formula below: wherein Z is O, S or -CH 2 - and a, b, c and d may each independently be 0, 1 or 2; the sum of a, b, c and d not exceeding 5; the broken line at the 22-23 position represents an optional double bond, wherein R 1 is H, OH, O-(C,-C 6 alkyl) oxo or optionally substituted oximino when the double bond is absent, or, the double bond is present and R 1 is absent; and R 2 and R 3 are independently H and OH, H and C,-C 6 alkoxy or H and C,- C 6 acyloxy, these radicals being attached to the remainder of the molecule by single bonds, or are oxo or optionally O - substituted oximino attached by a double bond, or in formula (I) or (II) R 2 is as defined above and R 3 is H, amino wherein said amino is optionally substituted with a C,-C„ alkyl, aralkyl or acyl group or a C 3 -C 8 alkenyl, or alkynyl group, with the proviso that when R 2 is H and OH, H and methoxy or oxo and R 3 is H and OH, in formula (I), (II) or (III) then R is not isopropyl or sec-butyl. 2. A compound according to claim 1 , in which R is a straight or branched-chain C,-C 8 alkyl, alkenyl or cycloalkyl group or a 5 - or 6 - membered oxygen - or sulphur - containing heterocyclic group. 3. A compound according to claim 2 in which R is a cyclohexyl, cyclobutyl or 3- thienyl group. 4. A compound according to claim 1 , 2 or 3 in which said optional bond is present or said optional bond is absent and R is H or OH or oximino. 5. A compound according to any preceding claim, in which R 2 is H, OH, oxo or oximino. 6. A compound according to any preceding claim, in which R 3 is H, OH or H, NHR 8 where R 8 is H, C,-C 8 alkyl or acyl. 8. A process for preparing a compound according to any one of claims 1 to 7 or a compound convertible thereto, which comprises fermenting micro-organism Streptomyces avermitilis ATCC 55372 in the presence of a carboxylic acid of formula RC0 2 H or a salt, ester or amide thereof where R is as defined in claim 1 to produce (a) a compound of formula (I) in which R 2 and R 3 are both H, OH and either the double bond at the 22-23 position is present and R 1 is absent, or (b) the compound of formula (II), in which R 2 is either H, OH or =0, R 3 is H, OH and either the double bond at the 22-23 position is present and R 1 is absent, or the double bond is absent and R 1 is OH and isolating the compound of formula (I) or (II) produced; if necessary followed by one or more of the following steps: (i) hydrolysing a compound of formula (I) to yield a compound of formula (II) or (III), or hydrolysing a compound of formula (II) to yield a compound of formula (III); (ii) converting H, OH at R 2 to H, OCH 3 in a compound of formula (I), (II) or (III) by reaction thereof with a methyl halide in the presence of silver oxide or a silver salt; (iii) oxidising a compound of formula (I), (II) or (III) in which R 2 or R 3 is H, OH and/or R 1 is OH to yield a compound in which at least one of R 1 and R 2 is oxo; (iv) allowing a compound obtained from (III) to react with optionally O-substituted hydroxylamine to produce an optionally substituted imino compound; (v) converting an oxo group at R 3 of a compound obtained from (III) to a compound of formula (I), (II) or (III) to amino by reductive amination; (vi) reacting a compound in which R 1 is OH with an alkyl bromide or iodide in the presence of silver oxide or a silver salt to produce a compound in which R 1 is -O-alkyl; (vii) reducing a compound of formula (I), (II) or (III) having a double bond at the 22-23 position with hydrogen to yield a compound having a single bond at the 22-23 position. 9. A compound according to any one of claims 1 to 7, for use in human or veterinary medicine. 10. Use of a compound according to any one of claims 1 to 7, for making a medicament for treatment or prophylaxis of parasitic infections. 11. A method of treatment or prophylaxis of parasitic infections, which comprises administering to a person or animal an effective antiparasitic amount of a compound according to any one of claims 1 to 7. 12. Streptomyces avermitilis. ATCC 55372.

Inventors: HAFNER EDMUND WILLIAM, MCARTHUR HAMISH ALASTAIR IRVIN, PACEY MICHAEL STEPHEN, PERRY DAVID AUSTEN, TYNAN EDWARD JOSEPH, HAFNER, EDMUND, WILLIAM, MCARTHUR, HAMISH, ALASTAIR, IRVINE, PACEY, MICHAEL, STEPHEN, PERRY, DAVID, AUSTEN, TYNAN, EDWARD, JOSEPH
Applicants: HAFNER EDMUND WILLIAM, MCARTHUR HAMISH ALASTAIR IRVIN, PACEY MICHAEL STEPHEN, PERRY DAVID AUSTEN, PFIZER, PFIZER LTD, TYNAN EDWARD JOSEPH, HAFNER, EDMUND, WILLIAM, MCARTHUR, HAMISH, ALASTAIR, IRVINE, PACEY, MICHAEL, STEPHEN, PERRY, DAVID, AUSTEN, PFIZER INC., PFIZER LIMITED, TYNAN, EDWARD, JOSEPH
Application year: 1993
Main classification: C07H17
IPC codes: A01N43, A23K1, A61K31, A61P33, C07D493, C07H17, C07H19, C12N1, C12P17, C12P19, C12R1