WO1992017474A1

WO1992017474A1 - Triazole antifungal agents

Info

Publication number: WO1992017474A1
Application number: PCT/EP1992/000697
Authority: WO
Inventors: Roger Peter Dickinson
Original assignee: Pfizer Corp Belgium; Pfizer Ltd Great Britain; Pfizer Corp SRL
Current assignee: Pfizer Corp Belgium; Pfizer Ltd Great Britain; Pfizer Corp SRL
Priority date: 1991-04-04
Filing date: 1992-03-26
Publication date: 1992-10-15
Anticipated expiration: 1993-10-04
Also published as: PT100331A; GB9107055D0; IE921059A1

Abstract

The invention provides antifungal compounds of formula (I) and pharmaceutically acceptable salts thereof, wherein R is phenyl optionally substituted by 1 to 3 substituents each independently selected from halo and CF3; R1 is C1-C4 alkyl; R2 is H or C¿1?-C4 alkyl; and 'Het' is oxazol-2-yl, thiazol-2-yl, 1,2,4-oxadiazol-3 or 5-yl, 1,2,4-thiadiazol-5-yl, 1,3,4-oxadiazol-2-yl or 1,3,4-thiadiazol-2-yl, all of which may be optionally substituted by C1-C4 alkyl or CF3, together with pharmaceutical compositions containing, and processes and intermediates used for the preparation of said compounds.

Description

TRIAZOIE ANTIFUNGAL AGENTS

This invention relates to triazole derivatives which have antifungal activity.

More particularly this invention relates to 2-aryl-3-heteroaryl-1-(1H-1,2,4-triazol-1-yl)alkan-2-ols which are useful in the treatment of fungal infections in animals, including human beings.

Same of the compounds of the present invention have been disclosed in a general sense in EP-A-0332387 but none of them are specifically disclosed or exemplified therein.

Ihe compounds of the present invention are particularly active as antifungal agents against certain clinically important species of fungus such as Candida spp., Aspergillus spp. or

Cryptococcus spp.

The invention provides triazole antifungal compounds of the formula:-

and the pharmaceutically acceptable salts thereof. wherein R is phenyl optionally substituted by 1 to 3

substituents each independently selected from halo and -CF₃;

R¹ is C₁-C₄ alkyl;

R² is H or C₁-C₄ alkyl; and

"Het" is oxazol-2-yl, thiazol-2-yl,

1,2,4-oxadiazol-3 or 5-yl, 1,2,4-thiadiazol-5-yl,

1,3,4-oxadiazol-2-yl or 1,3,4-thiadiazol-2-yl, all of which may be optionally substituted by C₁-C₄ alkyl or

-CF₃.

In the above definitions halo is fluoro, chloro, bromo or iodo and C₃ and C₄ alkyl groups may be straight or branched chain.

The preferred C₁-C₄ alkyl group is methyl.

Examples of R include 2-fluorophenyl, 4-fluorophenyl, 2-chlorophenyl, 4-chlorophenyl, 2-bromophenyl, 2-iodophenyl, 2-trifluoromethylphenyl, 2,4-dichloropιhenyl, 2,4-difluorophenyl, 2-chloro-4-fluorophenyl, 2-fluoro-4-chlorophenyl,

2,5-difluorophenyl, 2,4,6-trifluorophenyl and

4-bromo-2,5-difluorophenyl.

Preferably R is phenyl substituted by 1 to 3 halo

substituents. More preferably R is phenyl substituted by 1 or 2 halo substituents.

Yet more preferably R is phenyl substituted by 1 or 2 substituents each independently selected from fluoro and chloro. Particularly preferred individual embodiments of R include

2-fluorophenyl, 2-chlorophenyl, 2,4-difluorophenyl and

2,4-dichlorophenyl.

Preferably R¹ is C₁-C₄ alkyl and R² is H.

Most preferably R¹ is methyl and R² is H.

Preferably "Het" is oxazol-2-yl, thiazol-2-yl,

5-methyl-1,2,4-oxadiazol-3-yl, 3-methyl-1,2,4-oxadiazol-5-yl, 1,3,4-oxadiazol-2-yl, 5-methyl-1,3,4-oxadiazol-2-yl,

5-trifluoromethyl-1,3,4-oxadiazol-2-yl or 1,3,4-thiadiazol-2-yl.

Mbst preferably "Het" is 1,3,4-oxadiazol-2-yl or

1,3,4-thiadiazol-2-yl.

The pharmaceutically acceptable salts of the compounds of the formula (I) include acid addition salts formed from acids which form non-toxic salts such as the hydrochloride, hydrobromide, hydroiodide, sulphate or bisulphate, phosphate or hydrogen phosphate, acetate, maleate, fumarate, lactate, tartrate, citrate, gluconate, benzoate, oxalate, methanesulphonate, benzenesulphonate and p-toluenesulphonate salts. A compound of the formula (I) contains one or more chiral centres and as such exists in two or more stereoisomeric forms either as a pair of enantiomers or as two or more

diastereoisomeric pairs of enantiomers.

The invention includes both the individual stereoisomers of a compound of the formula (I) together with mixtures thereof.

Separation of diastereoisomers may be achieved by

conventional techniques, such as by fractional crystallisation, chromatography or H.P.L.C. of a diastereoisomeric mixture of a compound of the formula (I) or of a suitable salt or derivative thereof.

An individual enantiomer of a compound of the formula (I) may be prepared from either a corresponding optically pure

intermediate or by resolution, either by H.P.L.C. of the racemate using a suitable chiral support or by separation of the

diastereoisomeric derivatives formed by reacting the racemate with a suitable optically active reagent, for example by fractional crystallisation, chromatography or H.P.L.C, followed by

regeneration of the required enantiomer.

The compounds of the formula (I) provided by the invention may be prepared by the following methods:- 1) A compound of the formula (I) wherein R, R¹ and R² are as defined for a compound of the formula (I) and "Het" is 5-substituted-oxazol-2-yl, 4,5-disubstituted-oxazol-2-yl, 5-substituted-thiazol-2-y1, 4,5-disubstituted-thiazol-2-y1, optionally substituted 1,2,4-thiadiazol-5-yl or substituted 1,3,4-thiadiazol-2-yl may be prepared as shown in Scheme 1:-

Scheme 1

wherein R, R¹, R² and "Het" are as previously defined for this method.

In a typical procedure a compound of the formula (II) is deprotonated by the addition of approximately one equivalent of a suitable base, e.g. n-butyllithium or lithium diisopropylamide, and the resulting salt (preferably the lithium, sodium or potassium salt) is reacted in situ with a compound of the formula (I). The reaction is typically carried out at from -80° to 0°C, preferably at from -80°C to -30°C, in a suitable organic solvent, e.g. tetrahydrofuran or diethyl ether, and under an inert

atmosphere, e.g. nitrogen or argon. The product of the formula (I) may be isolated by conventional techniques.

A starting material of the formula (II) may be prepared by a conventional procedure in accordance with literature precedents.

A starting material of the formula (III) is either known, for example see EP-A-44605, EP-A-69442 or GB-A-1464224, or may be prepared by an analogous method to those used therein. 2) A compound of the formula (I) wherein R, R¹ and R² are as defined for a compound of the formula (I) and "Het" is unsubstituted oxazol-2-yl, 4-substituted-oxazol-2-yl, unsubstituted thiazol-2-yl or 4-substituted-thiazol-2-yl may be prepared as shown in Scheme 2:-

Scheme 2

wherein R, R¹ and R² are as previously defined for this method; X is O or S; Y is CH, C(C₁-C₄ alkyl) or C(CF₃); and Z is a suitable protecting group, preferably a suitable organosilyl group, e.g. trimethylsilyl or tert- butyldimethylsilyl.

In a typical procedure, where Z is a suitable organosilyl group such as trimethylsilyl or tert-butyldimethylsilyl, the deprotection is most conveniently carried out using a suitable source of fluoride ions. Suitable conditions include the use of aqueous hydrofluoric acid in acetonitrile or tetxabutylammoniiim fluoride in tetrahydrofuran. The deprotection is normally carried out at room temperature.

A starting material of the formula (IV) wherein Z is a suitable organosilyl group may be prepared as shown in Scheme 3:-

Scheme 3

wherein R, R¹, R², X and Y are as previously defined for a compound of the formula (IV).

In a typical procedure a compound of the formula (V) is deprotonated with approximately one equivalent of a suitable base, e.g. n-butyllithium, and the salt formed is reacted in situ with a suitable chloroorganosilane of the formula Z-Cl. The reaction is typically carried out at from -70° to 0°C, preferably at below -30°C, in a suitable organic solvent, e.g. tetrahydrofuran, and, after addition of the chloroorganosilane, a period of stirring at room temperature is often desirable. The product of the formula (VI) is isolated in a conventional manner.

A compound of the formula (VI) is converted to a compound of the formula (IV) by an analogous method to that previously described in method (1) for the preparation of compounds of the formula (I) (see Scheme 1).

A starting material of the formula (V) may be prepared by a conventional procedure in accordance with literature precedents, e.g. see Cornforth et al, J. Chem. Sec., 96 (1947) and Metzger et al. Bull. Chim. Soc. France, 4499 (1967). 3) A compound of the formula (I) wherein R, R¹ and R² are as defined for a compound of the formula (I) and "Het" is optionally substituted 1,2,4-oxadiazol-5-yl may be prepared as shown in Scheme 4:- Scheme 4

wherein R, R¹ and R² are as previously defined for this method and R is H, C₁-C₄ alkyl or -CF₃.

In a typical procedure a compound of the formula (VII) is heated, preferably at from 130° to 180°C, and preferably in the absence of solvent, to induce the desired intramolecular condensation reaction. The product of the formula (I) may be isolated by conventional techniques.

This preparation is based on conventional synthetic methodology, e.g. see Lenaers et al, Helv. Chim. Acta, 45, 441 (1962) and Middleton, J. Org. Chem, 49 (5), 919 (1984).

A starting material of the formula (VII) may be prepared by the route shown in Scheme 5:- Scheme 5

wherein R, R¹, R² and R³ are as previously defined for a compound of the formula (VII) and R⁴ is C₁-C₄ alkyl, preferably methyl or ethyl.

In a typical procedure an ester of the formula (VIII) is deprotonated with approximately one equivalent of a suitable base, e.g. lithium diisopropylamide, and the salt obtained is reacted in situ with a compound of the formula (III) under analogous conditions to those described in method (1) for the preparation of compounds of the formula (I) (see Scheme 1). The ester of the formula (IX) obtained is hydrolysed to a carboxylic acid of the formula (X) under conventional conditions, e.g. by heating with aqueous potassium hydroxide. The carboxylic acid of the formula (X) is first converted to an activated ester derivative, e.g. by reacting with dicyclohexylcarbodiimide and N-hydroxybenzotriazole, prior to treatment with an amidoxime of the formula (XI) to provide a compound of the formula (VII), the entire reaction being carried out in a suitable solvent, e.g. 1,4-dioxane, at roam temperature. 4) A compound of the formula (I) wherein R, R¹ and R² are as defined for a compound of the formula (I) and "Het" is optionally substituted 1,2,4-oxadiazol-3-yl may be prepared as shown in Scheme 6:-

Scheme 6

wherein R, R¹ and R² are as previously defined for this method and R⁵ is H, C₁-C₄ alkyl or -CF₃.

In a typical procedure a compound of the formula (XII) is heated, preferably at from 130° to 180°C, and preferably in the absence of solvent, to induce the desired intramolecular

condensation reaction. The product of the formula (I) is isolated by conventional techniques.

This preparation is based on conventional synthetic methodology, e.g. see lenaers et al, Helv. Chim. Acta, 45, 441 (1962).

A starting material of the formula (XII) may be prepared by the route shown in Scheme 7:-

Scheme 7

wherein R, R¹, R² and R⁵ are as previously defined for a compound of the formula (XII) and R⁶ is a suitable leaving group, e.g. -OCO(C₁-C₄ alkyl or -CF₃).

In a typical procedure a nitrile of the formula (XIII) is deprotonated with approximately one equivalent of a suitable base, e.g. n-butyllithium, and the salt obtained is reacted in situ with a compound of the formula (III) under analogous conditions to those described in method (1) for the preparation of compounds of the formula (I) (see Scheme 1) . The nitrile of the formula (XIV) is converted to an amidoxime of the formula (XV) by reaction with hydroxylamine under conventional conditions, e.g. by heating the reactants together in n-butanol at about 40°C. The amidoxime of the formula (XV) is preferably converted to a compound of the formula (XII) by acylation with an acid anhydride of the formula (XVT), the reaction typically being carried out in a suitable solvent, e.g. 1,4-dioxane, at from 0ºC to room temperature. 5) A compound of the formula (I) wherein R, R¹ and R² are as previously defined for a compound of the formula (I) and

"Het" is optionally substituted 1,3,4-oxadiazol-2-yl may be prepared as shown in Scheme 8:-

Scheme 8

wherein R, R¹ and R² are as previously defined for a compound of the formula (I) and R⁷ is H, C₁-C₄ alkyl or -CF₃.

In a typical procedure a compound of the formula (XVII) is heated at above room temperature to provide a compound of the formula (I). The reaction is preferably carried out in a suitable solvent, e.g. toluene, and at the reflux temperature thereof. The product of the formula (I) is isolated by conventional techniques.

A starting material of the formula (XVII) may be prepared by the route shown in Scheme 9.

Scheme 9

wherein R, R¹, R² and R⁷ are as previously defined for a compound of the formula (XVII) and R⁴ is as previously defined for a compound of the formula (IX).

In a typical procedure an ester of the formula (IX) is heated under reflux in ethanol with hydrazine hydrate to provide a hydrazide of the formula (XVIII). The hydrazide of the formula (XVIII) is then treated with an imidate of the formula (XIX), or an acid addition salt (e.g. hydrochloride) thereof, in a suitable solvent, e.g. ethanol, at from room temperature to the reflux temperature of the solvent to provide the compound of the formula (XVII). 6) A compound of the formula (I) wherein R, R ¹ and R² are as previously defined for a compound of the formula (I) and

"Het" is unsubstituted 1,3,4-oxadiazol-2-yl may be most conveniently prepared as shown in Scheme 10:-

Scheme 10

wherein R, R¹ and R² are as previously defined for a compound of the formula (I) and R ⁸ is C₁-C₄ alkyl, preferably methyl or ethyl.

In a typical procedure a compound of the formula (XXI) is heated to provide a compound of the formula (I). The reaction is preferably carried out in a suitable solvent, e.g. toluene, and at the reflux temperature thereof.

A compound of the formula (XXI) may be prepared by reacting a hydrazide of the formula (XVIII) with a trialkyl orthoformate of the formula (XX), preferably trimethyl or triethyl orthoformate.

It is most convenient to carry out the preparation of a compound of the formula (I) from a hydrazide of the formula

(XVIII) without isolation of the acyclic intermediate of the formula (XXI). In a typical procedure a hydrazide of the formula (XVIII) is heated together with an orthoformate of the formula (XX). Preferably the reaction is carried out in a suitable organic solvent, e.g. toluene, and at the reflux temperature thereof, and the product is isolated by conventional techniques. 7) A compound of the formula (I) wherein R, R ¹ and R² are as previously defined for a compound of the formula (I) and

"Het" is substituted 1,3,4-oxadiazol-2-yl may also be prepared as shown in Scheme 11, using conventional synthetic methodology, e.g. see Comprehensive Heterocyclic Chemistry,

Vol. 6., 444 (Pergamon Press, 1984) and Advances in

Heterocyclic Chemistry, 7, 183 (Academic Press, 1966). Scheme 11

y

wherein R, R ¹ and R² are as previously defined for a compound of the formula (I) and R⁹ is C₁-C₄ alkyl or -CF₃.

In a typical procedure a solution of an acyltetrazole of the formula (XXII) in a suitable organic solvent, e.g. xylene, is heated, preferably at the reflux temperature of the solvent, to provide the product of the formula (I) which is isolated by conventional techniques.

A starting material of the formula (XXII) may be prepared by the route shown in Scheme 12:-

Scheme 12

wherein R, R ¹ and R² are as previously defined for a compound of the formula (XXII).

In a typical procedure a compound of the formula (XIV) is treated with tri-n-butyltin azide at about 170°C to provide a tetrazole of the formula (XXIII). The tetrazole of the formula (XXIII) may be acylated to give an acyltetrazole of the formula

(XXII) under a variety of conventional conditions, e.g. using an acid halide of the formula R ⁹CO(Hal), wherein R ⁹ is C₁-C₄ alkyl or

-CF₃ and "Hal" is halo, preferably chloro, optionally in the presence of a suitable acid acceptor; using an acid anhydride of the formula (R ⁹CO)₂O, wherein R⁹ is C₁-C₄ alkyl or -CF₃; or using a carboxylic acid of the formula R ⁹COOH, wherein R ⁹ is C₁-C₄ alkyl or -CF₃, in the presence of a suitable dehydrating agent, e.g.

dicyclohexylcarbodiimide. The conversion of the tetrazole of the formula (XXIII) to the required product of the formula (I) is most conveniently

accomplished without isolating the intermediate acyltetrazole of the formula (XXII). In a typical procedure a tetrazole of the formula (XXIII) is mixed with a carboxylic acid of the formula R ⁹COOH and a suitable dehydrating agent, e.g. dicyclohexyl-carbodiimide, in a suitable solvent, e.g. xylene, and the mixture heated at above room temperature, usually at about the reflux temperature of the solvent, for several hours. The product of the formula (I) is then isolated in a conventional manner. 8) A compound of the formula (I) wherein R, R ¹ and R² are as previously defined for a compound of the formula (I) and

"Het" is optionally substituted 1,3,4-thiadiazol-2-yl may be prepared as shown in Scheme 13 using conventional synthetic methodology, e.g. see H. Eilingsfeld, Chem. Ber., 98, 1308

(1965):-

Scheme 13

wherein R, R¹ and R² are as previously defined for a compound of the formula (I) and R¹⁰ is H, C₁-C₄ alkyl or -CF₃.

In a preferred procedure a compound of the formula (XXIV) is treated with a suitable acid, e.g. acetic acid or, preferably, dichloroacetic acid. The reaction is generally carried out at room temperature but the mixture may be heated if required. The product of the formula (I) is isolated by conventional techniques.

A starting material of the formula (XXIV) may be prepared by a route shown in Scheme 14:-

Scheme 14

wherein R, R¹ and R² are as previously defined for a compound of the formula (XXIV).

In a typical procedure for preparing a compound of the formula (XXIV) where R¹⁰ is H, a hydrazide of the formula (XVIII) is treated with an acetal of the formula (XXV), preferably

N,N-dimethylformamide diethyl acetal, at an elevated temperature, preferably at about the reflux temperature of the acetal. The compound of the formula (XXVI) obtained is treated with hydrogen sulphide in the presence of a suitable acid, e.g. acetic acid, in a sui'table solvent, e.g. N,N-dimethylformamide, at room

10 temperature to provide a product of the formula (XXIV) wherein R is H. This route involves conventional synthetic methodology, e.g. see H. Eilingsfeld, Chem. Ber., 98, 1308 (1965).

In a typical procedure for preparing a compound of the formula (XXIV) where R¹⁰ is C₁-C₄ alkyl or -CF₃, a hydrazide of the formula (XXVII) is treated with a dithioester of the formula

(XXVII) in the presence of sodium hydroxide and in a suitable solvent, e.g. aqueous methoxyethanol, at about room temperature

(see H. Eilingsfeld, Chem. Ber., 98, 1308 (1965)).

All of the above reactions are conventional and appropriate reagents and reaction conditions for their performance and procedures for isolating the desired products will be well known to those skilled in the art, in accordance with literature precedents and by reference to the Examples hereto.

Pharmaceutically acceptable acid addition salts are readily prepared by mixing together solutions containing equimolar amounts of the free base and the desired acid. The salt generally precipitates from solution and is collected by filtration, or is recovered by evaporation of the solvent.

The compounds of the formula (I) and their salts are antifungal agents, useful in the curative or prophylactic treatment of fungal infections in animals, including humans. For example, they are useful in treating topical fungal infections in man caused by, among other organisms, species of Candida,

Trichophyton, Microsporum or Epidermophyton, or in mucosal infections caused by Candida albicans (e.g. thrush and vaginal candidiasis). They can also be used in the treatment of systemic fungal infections caused by, for example, Candida albicans,

Crγptococcus neoformans, Aspergillus flavus, Aspergillus

fumigatus, Coccidioides, Paracoccidioides, Histoplasma or

Blastomyces.

The compounds of the present invention have been found to have particularly good activity against certain clinically important species of fungus such as Candida spp., Aspergillus spp. or Cryptococcus spp. The in vitro evaluation of the antifungal activity of the compounds can be performed by determining the minimum inhibitory concentration (m.i.c), which is the concentration of the test compounds, in a suitable medium, at which growth of the particular micro-organism fails the occur. In practice, a series of agar plates, each having the test compound incorporated at a particular concentration, is inoculated with a standard culture of, for example, Candida albicans, and each plate is then incubated for 48 hours at 37°C. The plates are then examined for the presence or absence of growth of the fungus and the appropriate m.i.c. value is noted. Other micro-organisms used in such tests can include Aspergillus fumigatus, Crγptococcus spp., Trichophyton spp.,

Microsporum spp., Epidermophyton floccosum, Coccidioides immitis and Torulopsis glabrata.

The in vivo evaluation of the compounds can be carried out at a series of dose levels by intraperitoneal or intravenous

injection, or by oral administration, to mice which are inoculated with, e.g., a strain of Candida albicans or Aspergillus fumiqatus. Activity is based on the survival of a treated group of mice after the death of an untreated group of mice. The dose level at which the compound provides 50% protection against the lethal effect of the infection (PD₅₀) is noted. For Aspergillus spp. infection models, the number of mice cured of the infection after a set dose allows further assessment of activity. For human use, the antifungal compounds of the formula (I) and their salts can be administered alone, but will generally be administered in admixture with a pharmaceutical carrier selected with regard to the intended route of administration and standard pharmaceutical practice. For example, they can be administered orally in the form of tablets containing such excipients as starch or lactose, or in capsules or ovules either alone or in admixture with excipients, or in the form of elixirs or suspensions containing flavouring or colouring agents. They can be injected parenterally, for example, intravenously, intramuscularly or subcutaneously. For parenteral administration, they are best used in the form of a sterile aqueous solution which may contain other substances, for example, enough salts or glucose to make the solution isotonic with blood.

For oral and parenteral adminstration to human patients, the daily dosage level of the antifungal compounds of the formula (I) and their salts will be from 0.01 to 20 mg/kg (in single or divided doses) when administered by either the oral or parenteral route. Thus tablets or capsules of the compounds will contain from 5 mg to 0.5 g of active ccsipound for administration singly or two or more at a time, as appropriate. The physician in any event will determine the actual dosage which will be most suitable for an individual patient and it will vary with the age, weight and response of the particular patient. The above dosages are exemplary of the average case; there can, of course, be individual instances where higher or lower dosage ranges are merited, and such are within the scope of this invention. Alternatively, the antifungal compounds of the formula (I) can be administered in the form of a suppository or pessary, or they may be applied topically in the form of a lotion, solution, cream, ointment or dusting powder. For example, they can be incorporated into a cream consisting of an aqueous emulsion of polyethylene glycols or liquid paraffin; or they can be

incorporated, at a concentration between 1 and 10%, into an ointment consisting of a white wax or white soft paraffin base together with such stabilizers and preservatives as may be required.

Thus the invention further provides a pharmaceutical composition comprising a compound of the formula (I), or a pharmaceutically acceptable salt thereof, together with a pharmaceutically acceptable diluent or carrier.

The invention yet further provides a compound of the formula (I), or a pharmaceutically acceptable salt or composition thereof, for use as a medicament.

The invention also provides the use of a compound of the formula (I), or of a pharmaceutically acceptable salt or

composition thereof, for the manufacture of an antifungal agent.

The invention yet further provides a method of treating an animal (including a human being) to cure or prevent a fungal infection, which comprises treating said animal with an effective amount of a compound of the formula (I), or with, as appropriate, a pharmaceutically acceptable salt or composition thereof.

The invention also includes the novel intermediates of the formulae (XVII), (XXI) and (XXIV). The following Examples illustrate the preparation of the compounds of the formula (I) :-

EXAMPIE 1

2-(2 ,4-Difluorophenyl) -3-(oxazol-2-yl) -1-(1H-1, 2 ,4- triazol-1-yl)butan-2-ol

i) N-(Ethoxycarbonylmethyl)propionimidic acid ethyl ester

An intimate mixture of ethyl propionimidate hydrochloride (19.0g) and glycine ethyl ester hydrochloride (I9.3g) was added in one portion to a vigorously stirred mixture of ether (200ml) and a solution of potassium hydroxide (9.3g) in water (30ml). Stirring was continued for 15 minutes and the ether layer was separated. The aqueous layer was washed four times with ether and the combined organic layers were washed with water and dried (Na₂SO₄). Evaporation of the solvent gave an oil which was distilled under reduced pressure to give the title compound (11.8g), b.p. 102°-108°C @ 15mm.

The product was used directly in the next stage.

(ii) 2-Ethyloxazole-4-carboxylic acid ethyl ester

A solution of the product of part (i) (11.75g) and ethyl formate (6.40g) in tetrahydrofuran (50ml) was added over 10 minutes to a mixture of pxatassium t-butoxide (6.50g) in tetrahydrofuran (100ml) at from -20° to -10ºC under nitrogen. The mixture was stirred at -10°C for 2 hours and then dry ether (100ml) was added. The mixture was allowed to stand at 0°-5°C civernight and the solid was filtered off under dry nitrogen and washed with ether.

The solid was added portionwise to refluxing acetic acid (15ml) and refluxing was continued for 20 minutes. The acetic acid was evaporated under reduced pressure and the residue was partitioned between dichlorαmethane and dilute ammonia solution. The organic layer was separated and the aqueous layer was washed with dichloromethane. The combined organic layers were washed with dilute sodium bicarbonate solution and dried (Na₂SO₄). Evaporation of the solvent gave an oil which was chromatographed on silica gel.

Elution with ether/hexane (1:1) gave, after combination and evaporation of appropriate fractions, the title compound as an oil (4.90g).

(iϋ) 2-Ethyloxazole-4-carboxylic acid

The product of part (ii) (4.80g) was added to a solution of sodium hydroxide (1.20g) in water (15ml), and sufficient methanol was added to give a homogeneous solution. The solution was allcwed to stand for 2 hours, evaporated to a small volume and then acidified to pH3 with 2N hydrochloric acid. The solution was continuously extracted with dichlorcauethane for 18 hours. The extract was dried

(Na₂SO₄), filtered and evaporated to give the title compound as a hemihydrate (3.75g), m.p. 75°-76°C.

Analysis %:-

Found: C, 47.91; H, 5.31; N, 9.26 C₆H₇NO₃.½H₂O requires: C, 48.00; H, 5.37; N, 9.33

(iv) 2-Ethyloxazole

A mixture of the product of part (iii) (3.70g) and cuprous oxide (50mg) in quinoline was heated at 180°-200°C for 2 hours in a distillation apparatus and the distillate was collected. The temperature was then raised just to the boiling point of quinoline for 5 minutes. The total distillate was redistilled to give the title compound as an oil (1.75g), b.p. 100-120°C @ atmospheric pressure.

(v) 2-Ethyl-5--trimethylsilyloxazole

n-Butyllithium (11.0ml of 1.6M solution in hexane) was added to a solution of the product of part (iv) (1.70g) in dry tetrahydrofuran (40ml) at from -50° to -30°C under an atmosphere of dry nitrogen. The solution was stirred at -50°C for 30 minutes and then chlorotrimethylsilane (2.28g) was added dropwise. The cooling bath was removed and the mixture was allowed to warm to room temperature. Sodium bicarbonate solution and ether were added and the organic layer was separated, washed with brine and dried (Na₂SO₄). Evaporation of the solvent gave an oil which was distilled to give the title compound (1.90g), b.p. 66°-68°C @ 15mm.

The product was used directly in the next stage. (vi) 2-(2 ,4-Difluorophenyl)-3-(oxazol-2-yl)-1-(1H-1,2,4- triazol-1-yl)butan-2-ol

n-Butyllithium (6.3ml of a 1.6M solution in hexane) was added dropwise to a stirred solution of the product of part (v) (1.70g) in dry tetrahydrofuran (40ml) at -50°C under an atmosphere of dry nitrogen. The orange solution was stirred at -50°C for 30 minutes and then a solution of

1-(2,4-difluorophenyl)-2-(1H-1,2,4-triazol-1-yl)ethanone (2.33g) in dry tetrahydrofuran (10ml) was added over 3 minutes. Stirring was continued at the same temperature for 1 hour and then acetic acid (Iml) was added. The solution was allowed to warm to room temperature and water and ethyl acetate were added. The organic layer was separated, washed with water and dried (Na₂SO₄) . The solvent was evaporated to give a residue which was shown by tic (SiO₂/ethyl acetate) to consist of a mixture of two products

(diastereoisomeric pairs of enantiomers) and the two starting materials. The crude product was chromatographed on silica gel. Elution with ethyl acetate/hexane (3:7) first gave the oxazole starting material followed by the less polar pair of enantiomers. Further elution with ethyl acetate/hexane (1:1) gave a mixture of the ketone starting material and the more polar pair of enantiomers. The fractions containing the less polar pair of enantiomers were combined, evaporated and the residue was dissolved in acetonitrile (10ml) and 40% hydrofluoric acid (0.4ml) was added. The solution was allowed to stand at room

temperature for 5 hours, then diluted with ethyl acetate and washed with sodium bicarbonate solution. The organic layer was washed with brine and dried (Na₂SO₄). The solvent was evaporated and the residue was chrαmatographed on silica gel. Elution with ethyl acetate gave, after combination and evaporation of appropriate fractions, a product which crystallised from ether/hexane to give the title compound, enantiomeric pair A (less polar), (505mg) , m.p. 110°-112°C. Analysis %:-

Found: C, 56.19; H, 4.43; N, 17.35

C₁₅H₁₄F₂N₄O₂ requires: C, 56.24; H, 4.41; N, 17.50

The more polar pair of enantiomers containing ketone starting material was treated similarly with hydrofluoric acid. Work-up and ctaomatography as described above gave the title compound, enantiomeric pair B (more polar), (340mg), m.p.

106°-107°C (from ether/hexane).

Analysis %:-

Found: C, 56.23; H, 4.34; N, 17.36

C₁₅H₁₄F₂N₄O₂ requires: C, 56.24; H, 4.41; N, 17.50 EXAMPLE 2

2-(2 ,4-Difluorophenyl)-3-(thiazol-2-yl) -1-(1H-1, 2 ,4-triazol-1-yl)butan-2-ol

i) 2-Ethyl-5-trimethylsilylthiazoIe

Treatment of 2-ethylthiazole (Bull. Soc. Chim. France, 4499, (1967) ) (8.70g) with n-butyllithium and chlorotrimethylsilane according to the method of Example 1(v) gave the title compound (12.36g) , b.p. 90°-92°C @ 10mm. (ii) 2-(2,4-Difluorophenyl)-3-(thiazol-2-yl)-1-(1H-1,2,4- triazol-1-yl)butan-2-ol

Treatment of the product of part (i) (1.85g) with

n-butyllithium followed by 1-(2,4-difluorophenyl)-2- (1H-1,2,4-triazol-1-yl)ethanone according to the method of Example 4(vi) gave two diastereoisomeric pairs of

enantiomers. The pairs of enantiomers were separated and individually deprotected with hydrofluoric acid as described in Example 1(vi) to provide:- a) the title compound, enantiomeric pair A (less polar), (770mg), m.p. 129°-130°C (from dichlorcmethane/ether).

Analysis %:-

Found: C, 53.61; H, 4.18; N, 16.62

C₁₅H₁₄F₂N₄OS requires: C, 53.56; H, 4.20; N, 16.67 b) the title compound, enanticmeric pair B (more polar), (1.04g), m.p. 155°-156°C (from dichloromethane/ether).

Analysis %:-

Found: C, 53.34; H, 4.18; N, 16.59

C₁₅H₁₄F₂N₄OS requires: C, 53.56; H, 4.20; N, 16.67

EXAMPLE 3

2-(2-Chlorophenyl) -3-(thiazol-2-yl)-1-(1H-1 ,2 ,4- triazol-1-yl)butan-2-ol

Treatment of 2 -ethyl-5-trimethylsilylthiazole (the product of Example 2(i) ) (1.85g) with n-butyllithium and

1-(2-chlorophenyl)-2-(1H-1,2,4-triazol-1-yl)ethanone according to the method of Example 1(vi) gave two diastereoisomeric pairs of enantiomers. The pairs of enantiomers were separated and individually deprotected with hydrofluoric acid as described in Example 1(vi) to provide:- a) the title compound, enantiomeric pair A (less polar) ,

(405mg) , m.p. 114° -115ºC ( from ether) .

Analysis %:-

Found: C, 53.95; H, 4.53 ; N, 16.51

C₁₅H₁₅ClN₄OS requires: C, 53.80; H, 4.52 ; N, 16.74 b) the title compound, enantiomeric pair B, (more polar),

(1.14g), m.p. 146° -147.5ºC (from dichloromethane/ether) Analysis %:-

Found: C, 53.65; H, 4.34; N, 16.58

C₁₅H₁₅ClN₄OS requires: C, 53.80; H, 4.52; N, 16.74

EXMPLE 4

2-(2,4-Difluorophenyl)-3-(5-methyl-1,3,4-oxadiazol-2-yl)- 1-(1H-1,2,4-triazol-1-yl)butan-2-ol

" Ethyl 3-(2,4-difluorophenyl)-3-hydroxy-2-methyl-4-(1H-1,2,4-triazol-1-yl)butanoate

n-Butyllithium (93.75ml of a 1.6M solution in hexane) was added to a stirred solution of diisopropylamine (15.18g) in dry tetrahydrofuran (525ml) at -70°C under an atmosphere of dry nitrogen. The solution was stirred at -70°C for 10 minutes, followed by 10 minutes at 0°C and then it was re-cooled to -70°C. Ethyl propanoate (15.32g) was added dropwise and stirring was continued at -70°C for 30 minutes. A solution of 1-(2,4-difluorophenyl)-2-(1H-1,2,4-triazol-1-yl)ethanone (33.48g) in dry tetrahydrofuran

(150ml) was added over 10 minutes. The solution was stirred at -70°C for 2 hours, acetic acid (7.5mL) was added and the solution was allowed to warm to room temperature. The solution was diluted with water and extracted several times with ethyl acetate. The combined organic layers were washed with water and dried (Na₂SO₄). The solvent was evaporated and the residue was triturated with ether. The solid

(starting ketone) was filtered off and the filtrate was evaporated. The residue was chromatographed on silica gel using ethyl acetate/hexane (70:30) as eluent. The product fractions were combined and evaporated to give the title compound as an oil (29.75g) consisting of a mixture of the two diastereoisomeric pairs of enantiomers. (ii) 3-(2 ,4-Difluorophenyl)-3-hydroxy-2-methyl-4-(1H-1,2,4- triazol-1-γl)butanoic hydrazide

A solution of the product of part (i) (29.75g) and 98% hydrazine hydrate (4.37ml) in ethanol (100ml) was heated under reflux for 16 hours. Additional hydrazine hydrate (4.37ml) was added and heating was continued for a further 48 hours. The solution was evaporated and the residue was crystallised from dichloromethane. The solid was filtered off and recrystallised from acetonitrile to give the title compound (10.77g) as a mixture of diastereoiscmeric pairs of enantiomers, m.p. 160°-162°C.

Analysis %:-

Found: C, 50.17; H, 4.89; N, 22.50

C₁₃H₁₅F₂N₅O₂ requires: C, 50.16; H, 4.86; N, 22.50

The mother liquors from the crystallisations were combined and evaporated, and the residue was chromatographed on silica gel. Initial elution with dichloromethane/methanol (20:1) gave some impurity. Addition of 1% 0.880 ammonia solution to the eluent gave additional title compound as a mixture of diastereoisomeric pairs of enantiomers (1.88g). Further elution with the same solvent gave the pure more polar enantiomeric pair, (4.00g), m.p. 182 °C (from acetonitrile).

Analysis %:-

Found: C, 50.22; H, 4.83; N, 22.80

C₁₃H₁₅F₂N₅O₂ requires: C, 50.16; H, 4.86; N, 22.50 (iii) 2-(2,4-Difluorophenyl)-3-(5-methyl-1,3,4-oxadiazol-2-yl)- 1-(1H,1,2,4-triazol-1-yl)butan-2-ol

A solution of the product of part (ii) (2.0g of a mixture of diastereoisomeric pairs of enantiomers) and ethyl

acetimidate hydrochloride (2.1g) in ethanol (20ml) was heated under reflux for 1 hour and then stirred at room temperature for 18 hours. The solution was evaporated and the residue was chromatographed on silica gel. Elution with dichloromethane/methanol (50:1) gave, after combination and evaporation of appropriate fractions, the acyclic

intermediate as a stereoisomeric mixture. This intermediate was dissolved in toluene and the solution was heated under reflux for 60 hours and then evaporated. The residue was chromatographed on silica gel using ether/methanol (20:1) as eluent. The relevant fractions were combined and evaporated to give, in order of elution:- a) the title compound, enantiomeric pair A, (108mg), m.p.

180°-182°C (from dichloromethane/ether).

Analysis %:- Found: C, 53.43; H, 4.48; N, 20.60 C₁₅H₁₅F₂N₅O₂ requires: C, 53.73; H, 4.51; N, 20.89 b) the title compound, enantiomeric pair B, (287mg), m.p.

126°-128°C (from dichlorcroethane/ether).

Analysis %:-

Found: C, 53.69; H, 4.46; N, 21.23 C₁₅H₁₅F₂N₅O₂ requires: C, 53.73; H, 4.51; N, 20.89 EXAMPLE 5

2-(2 ,4-Difluorophenyl) -3-(1, 3 ,4-oxadiazol-2-yl) -1- (1H-1, 2 ,4-triazol-1-yl)butan-2-ol

A solution of the product of Example 4(ii) (500 mg, pure more polar enanticameric pair) and trimethyl orthoformate (204mg) in toluene (5ml) was heated under reflux for 72 hours and then evaporated. The residue was chromatographed on silica gel using dichloromethane/methanol (33:1) as eluent. The product fractions were combined and evaporated and the residue was crystallised from dichlorcimethane/ether to give the title compound as a single enantiomeric pair, (240 mg), m.p. 156°-157°C.

Analysis %:-

Found: C, 52.67; H, 4.07; N, 21.49 C₁₄H₁₃F₂N₅O₂ requires: C, 52.33; H, 4.08; N, 21.80 EXAMPLE 6

2-(2-Chlorophenyl)-3-(1,3,4-oxadiazol-2-yl)-1-(1H-1,2,4-triazol-1-yl)butan-2-ol

(i) Ethyl 3-(2-chlorophenyl)-3-hydroxy-2-methyl-4-(1H-1,2,4- triazol-1-yl)butanoate

Treatment of 1-(2-chlorophenyl)-2-(1H-1,2,4-triazol-1-yl)- ethanone (26.0g) with four molar equivalents of the anion derived by deprotonation of ethyl propanoate with lithium diisopropylamide according to the method of Example 4(i) gave the title compound (23.4g) as a mixture of

diastereoisomeric pairs of enantiomers.

(ii) 3-(2-Chlorophenyl)-3-hydroxy-2-methyl-4-(1H-1,2,4- triazol-1-yl)butanoic hydrazide

Treatment of the product of part (i) (22.5g) with hydrazine hydrate according to the method of Example 4(ii) gave the title compound (16.5g) as a mixture of diastereoisomeric pairs of enantiomers, m.p. 168°-200°C.

Analysis %:-

Found: C, 50.24; H, 5.27; N, 22.49

C₁₃H₁₆ClN₅O requires: C, 50.41; H, 5.21; N, 22.61

(iii) 2-(2-Chlorophenyl)-3-(1,3,4-oxadiazol-2-yl)-1-(1H-1,2,4- triazol-1-yl)butan-2-ol

Treatment of the product of part (ii) (1.0g) with trimethyl orthoformate according to the method of Example 5 gave a crude solid which was triturated with ether and filtered. The solid was crystallised from ethyl acetate to give the title compound as a single enantiomeric pair, (305 mg), m.p. 156°-157°C. Analysis %:- Found: C, 52.56; H, 4.61; N, 21.59

C₁₄H₁₄FlN₅O₂ requires: C, 52.59 ; H, 4.41; N, 21.90

The other enanticsneric pair remained in the ether washings and was not investigated further.

EXAMPLE 7

2-(2 ,4-Difluorophenyl)-3-(1,3 ,4-thiadiazol-2-yl) -1- (1H-1,2 ,4-triazol-1-yl)butan-2-ol

(i) N-[3-(2 ,4-Difluorophenyl)-3-hydroxy-2-methyl-4-( 1H-1,2 ,4- triazol-1-yl)]butanoyl-N'-[dimethylaminomethylene]hydrazine A mixture of 3-(2,4-difluorophenyl)-3-hydroxy-2-methyl-4- (1H-1,2,4-triazol-1-yl)butanoic hydrazide (1.87g of the pure more polar enantiomeric pair of Example 4(ii)) and

N,N-dimethylformamide diethyl acetal (10ml) was heated under reflux for 1.5 hours and then evaporated. The solid was triturated with ether and filtered to give the title compound as a single enantiomeric pair, (2.01g), m.p.

195°-196°C.

Analysis %:-

Found: C, 52.20; H, 5.42; N, 22.67

C₁₆H₂₀F₂N₆O₂ requires: C, 52.45; H, 5.50; N, 22.94

(ii) N-[3-(2,4-Difluorophenyl)-3-hydroxy-2-methyl-4-(1H-1,2,4- triazol-1-yl)]butanoyl-N'-[thioformyl]hydrazine

The product of part (i) (1.90g) was suspended in a mixture of N,N-dimethylformamide (7ml) and acetic acid (0.35ml) and hydrogen sulphide was passed through at a slow rate for 45 minutes. The resulting solution was allowed to stand for 1 hour and nitrogen was passed through the solution to remove excess hydrogen suljphide. The solution was poured into water and the mixture was extracted several times with ethyl acetate. The combined extracts were washed with brine and dried (Na₂SO₄). Evaporation of the solution gave a solid which was crystallised from dichloromethane to give the title compound as a single enantiomeric pair, (1.65g), m.p. 197°-198°C. (iii) 2-(2,4-Difluorophenyl)-3-(1,3,4-thiadiazol-2-yl)-1- (1H-1,2,4-triazol-1-yl)butan-2-ol

A mixture of the product of part (ii) (1.50g) and

dichloroacetic acid (6ml) was stirred at about 90°C for 30 minutes to give a clear solution. The solution was allowed to stand at room temperature for 18 hours and then

neutralised cautiously by the addition of solid sodium bicarbonate. The mixture was partitioned between water and ethyl acetate. The organic layer was separated and washed with aqueous sodium bicarbonate solution and dried (Na₂SO₄). Evaporation of the solvent gave a solid which was

crystallised from methanol to give the title compound as a single enantiomeric pair, (0.87g), m.p. 190°-192°C.

Analysis %:-

Found: C, 49.56; H, 3.77; N, 20.77

C₁₄H₁₃F₂N₅OS requires: C, 49.84; H, 3.88; N, 20.76

EXAMPLE 8

2-(2-Chlorophenyl)-3-(1,3,4-thiadiazol-2-yl)-1-(1H-1,2,4-triazol-1-yl)butan-2-ol

(i) N-[3-(2-Chlorophenyl)-3-hydroxy-2-methyl-4-(1H-1,2,4- triazol-1-yl)]butanoyl-N'-[dimethylaminomethylene]hydrazine Treatment of 3-(2-chlorophenyl)-3-hydroxy-2-methyl-4- (1H-1,2,4-triazol-1-yl)butanoic hydrazide (the

diastereoisomeric product mixture of Example 6(ii)) (3.0g) with N,N-dimethylformamide diethyl acetal (15ml) according to the method of Example 7(i) gave the title compound

(2.80g), m.p. 213°-216°C. (ii) N-[3-(2-Chlorophenyl)-3-hydroxy-2-methyl-4-(1H-1,2,4- triazol-1-yl)]butanoyl-N'-[thioformyl]hydrazine

Treatment of the product of part (i) (2.80g) with hydrogen sulphide according to the method of Example 7(ii) gave the title compound as an amorphous foam (2.50g) which was used without characterisation in the next step.

(iii) 2-(2-Chlorophenyl)-3-(1,3,4-thiadiazol-2-yl)-1-(1H-1,2,4- triazol-1-yl)butan-2-ol

Treatment of the product of part (ii) (2.50g) with dichloroacetic acid according to the method of Example 7(iii) gave a crude product which was chromatographed on silica gel. Elution with ethyl acetate/hexane (3:2) gave fractions containing a single enantiomeric pair. Further elution with ethyl acetate/hexane (3:1) gave fractions containing a mixture of diastereoisomeric pairs of enanticaners.

The earlier fractions containing a single enantiomeric pair were combined and evaporated and the residue was

crystallised from dichloromethane/ether to give the title compound as a single enantiomeric pair, (0.72g), m.p.

158°-161°C.

Analysis %:-

Found: C, 50.02; H, 4.31; N, 20.72

C₁₄H₁₄.ClN₅OS requires: C, 50.09; H, 4.20; N, 20.86 The column fractions containing the mixture of

diastereoisomeric pairs of enantiomers were not investigated further.

EXAMPLE 9

2-(2-Fluorophenyl)-3-(1,3,4-thiadiazol-2-yl)-1-(1H-1,2,4- triazol-1-yl)butan-2-ol

ET (i) Ethyl 3-(2-fluorophenyl)-3-hydroxy-2-methyl-4-(1H-1,2,4- triazol-1-yl)butanoate

Treatment of 1-(2-fluorophenyl)-2-(1H-1,2,4-triazol-1-yl) ethanone (5.10g) with four molar equivalents of the anion derived by deprotonation of ethyl propanoate with lithium diisopropylamide according to the method of Example 4(i) gave an oil which was chromatograpSied on silica gel using ethyl acetate/hexane (1:1) as eluent. The appropriate early product-containing fractions were combined and evaporated to give an oil (2.50g) consisting of a single enantiomeric pair of the title ccarpound which was used directly in the next step.

(ii) 3-(2-Fluorophenyl)-3-hydroxy-2-methyl-4-(1H-1,2,4- triazol-1-yl)butanoic hydrazide

Treatment of the product of part (i) (2.50g) with hydrazine hydrate according to the method of Example 4(ii) gave the title compound as a single enantiomeric pair, (2.30g), m.p. 190°-192°C.

(iii) N-[3-(2-Fluorophenyl)-3-hydroxy-2-methyl-4-(1H,1,2,4- triazol-1-yl)1butanoyl-N'-[dimethylaminomethylenelhydrazine Treatment of the product of part (ii) (2.30g) with

N,N-dimethylformamide diethyl acetal according to the method of Example 7(i) gave the title compound as a single enantiomeric pair, (2.20g), m.p. 181°-182°C. (iv) N-[3-(2-Fluorophenyl)-3-hvdroxy-2-methyl-4-(1H-1,2,4- triazol-1-yl)]butanoyl-N'-[thioformyl]hydrazine

Treatment of the product of part (iii) (2.20g) with hydrogen sulphide according to the method of Example 7(ii) gave the title compound as a single enantiomeric pair, (1.74g), m.p. 192°-193°C.

(v) 2-(2-Fluorophenyl)-3-(1,3,4-thiadiazol-2-yl)-1-(1H-1,2,4- triazol-1-yl)butan-2-ol

Treatment of the product of part (iv) (1.74g) with

dichloroacetic acid according to the method of Example 7 (iii) gave the title compound as a single enantiomeric pair (0.80g), m.p. 148°-149°C (from isopropanol).

NMR (CDCl₃): δ = 1.2 (d, 3H, CH₃), 4.0 (d, 1H) and 5.05 (d, 1H, CH₂), 4.38 (q, 1H, CHCH₃), 5.35 (s, 1H, OH), 7.0-7.1 (m, 2H, arom.), 7.27 (m, 1H, arom.), 7.5 (m, 1H, arom.), 7.74 (s, 1H, triazole H) , 7.79 (s, 1H, triazole H), 9.15 (s, 1H, thiadiazole H) ppm.

EXAMPLE 10

2-(2 ,4-Difluorophenyl) -3-(5-methyl-1,2 ,4-oxadiazol-3-yl) -1- 1,2 ,4-triazol-1-yl)butan-2-ol oxalate

3-(2 ,4-Difluorophenyl)-3-hydroxy-2-methyl-4-(3H-1,2,4- triazol-1-yl)butanenitrile

Propionitrile (24.2g) was added over 30 minutes to a stirred solution of n- butyllithium (275 ml of a 1.6 M solution in hexane) in dry tetrahydrofuran (600 ml) at -75°C under an atmosphere of dry nitrogen. The solution was stirred for 10 minutes and then a solution of 1-(2,4-difluorophenyl) -2- (1H-1,2 ,4-triazol-1-yl)ethanone (44.6g) in dry tetrahydrofuran (200 ml) was added with stirring at such a rate that the temperature did not exceed -60°C. Stirring was continued at -75°C for 10 minutes and then acetic acid

(30 ml) was added. The solution was allowed to warm to room temperature and then partitioned between water and ether. The organic layer was separated and washed with brine, dried

(Na₂SO₄) and evaporated to reduced volume until a solid crystallised out. The solid was filtered off, washed with ether and dried to give the title compound (20.1g) as a single enantiomeric pair, m.p. 182°-184°C.

(ii) 3-(2,4-Difluorophenyl)-N,3-dihydroxy-2-methyl-4-(1H-1,2,4- triazol-1-yl)butanimidamide

Sodium hydride (0.80g of a 60% dispersion in mineral oil) was added to n-butanol (10 ml) and the solution was stirred until the effervescence had ceased. The resulting solution was added dropwise to a stirred suspension of finely ground hydroxylamine hydrochloride in n-butanol (10 ml). The mixture was stirred for 2.5 hours and then filtered. The product from part (i) (0.93g) was added to the filtrate and the mixture was stirred at 40°C for 36 hours and then evaporated. The residue was triturated with hexane to give the title compound as a single enantiomeric pair as a gum, (0.92g), which was used directly in the next stage. (iii) N-Acetoxy-3-(2 ,4-difluorophenyl)-3-hydroxy-2-methyl-4- (1H-1,2,4-triazol-1-yl)butanimidamide

A solution of the product of part (ii) (0.92g) and acetic anhydride (0.5ml) in 1,4-dioxane (5 ml) was stirred at 0°C for 1 hour and then at room temperature for 16 hours. The solution was evaporated and the residue was chromatographed on silica gel. Elution with dichlorcmethane/methanol (100:1) and finally with dichlorcmethane/metlianol/

concentrated aqueous ammonia (90:10:1.5) gave, after combination and evaporation of appropriate fractions, the title ccmpound as a single enanticaneric pair as an oil (0.405g).

(iv) 2-(2,4-Difluorophenyl)-3-(5-methyl-1,2,4-oxadiazol-3-yl)- 1-(1H-1,2,4-triazol-1-yl)butan-2-ol oxalate

The product of part (iii) was heated at 160°C for 45 minutes and cooled. Ihe coloured impurity was removed by passage through a short column of silica gel using a mixture of dichlorometiiane/methanol/concentrated aqueous ammonia (100:5:1) as solvent. Evaporation of the eluate gave an amorphous foam which was dissolved in ether and treated with an ethereal solution of oxalic acid. The solid was filtered off, washed with ether and dried to give the title compound as a single enantiomeric pair as the oxalate salt (0.18g), m.p. 145-6°C.

Analysis %:-

Found: C, 48.55; H, 4.09; N, 16.04

C₁₅H₁₅F₂N₅O₂.C₂H₂O₄ requires: C, 48.00; H, 4.03; N, 16.47 EXAMPLE 11

2-(2,4-Difluorophenyl)-3-(3-methyl-1,2 ,4-oxadiazol-5-yl) -1- (1H-1, 2 ,4-triazol-1-yl)butan-2-ol

(i) 3-(2 ,4-Difluorophenyl)-3-hydroxy-2-methyl-4-(1H-1,2,4- triazol-1-yl)butanoic acid

Ethyl 3-(2,4-difluorophenyl) -3-hydroxy-2-methyl-4- (1H-1,2,4-triazol-1-yl)butanoate was prepared as a mixture of diastereoisomeric pairs of enantiomers as described in Example 4 (i) . Chromatography of this product on silica gel using hexane/ isopropanol (9:1) as eluent gave, after combination and evaporation of appropriate fractions, the less polar enantiomeric pair as an oil. A solution of this enantiomeric pair (5.0g) and potassium hydroxide (2.50g) in isopropanol (20 ml) and water (2 ml) was heated under reflux for 30 minutes and the isopropanol was distilled off. The solution was acidified to pH1 with hydrochloric acid and the solid was filtered off, washed with water and crystallised from isopropanol to give the title compound as a single enantiomeric pair, (3.12g), m.p. 189°-190°C.

Analysis %:-

Found: C, 52.80; H, 4.48; N, 14.21

C₁₃H₁₄F₂N₃O₃ requires: C, 52.52; H, 4.41; N, 14.14

(ii) N-[3-(2,4-Difluorophenyl)-3-hydroxy-2-methyl-4-(1H-1,2,4- triazol-1-yl)butanoyloxylacetimidamide

A solution of dicyclohexylcarbodiimide (0.69g) in dry dioxan (5 ml) was added to a stirred suspension of the product of part (i) (1.0g) and N-hydroxybenzotriazole hydrate (0.45g) in dry 1,4-dioxane (20 ml) . The mixture was stirred for 1 hour and then filtered. The filtrate was added to a stirred mixture of acetamidoxime (0.25g) and sodium carbonate

(0.38g) in dry 1,4-dioxane (10 ml) and the resulting mixture was stirred at room temperature for 24 hours. The solvent was evaporated and the residue was stirred with water and filtered. The solid was washed with water, dried and crystallised from ethyl acetate to give the title compound as a single enantiomeric pair, (0.79g), m.p. 149°-154°C. (iii) 2-(2 ,4-Difluorophenyl)-3-(3-methyl-1,2,4-oxadiazol-5-yl)-1- (1H-1,2,4-triazol-1-yl)butan-2-ol

The product of part (iii) was heated at 160°C for 2 hours and then cooled. The residue was chromatographed on silica gel. Elution was commenced with hexane/ethyl acetate (9:1), gradually increasing the proportion of ethyl acetate until the product was eluted. The product fractions were combined and evaporated and the residue was crystallised from ether/hexane to give the title compound as a single enantiomeric pair, (0.40g), m.p. 98º-99ºC.

Analysis %:-

Found: C, 53.75; H, 4.46; N, 20.50

C₁₅H₁₅F₂N₅O₂ requires: C, 53.73; H, 4.51; N, 20.89

EXAMPLE 12

2-(2,4-Dichlorophenyl)-1-(1H-1,2,4-triazol-1-yl)-3- (5-trifluoromethyl-1,3,4-oxadiazol-2-yl)butan-2-ol

(i) 3-(2 ,4-Dichlorophenyl)-3-hydroxy-2-methyl-4-(1H-1,2,4- triazol-1-yl)butanenitrile

Treatment of 1-(2,4-dichlorophenyl)-2-(1H-1,2,4- triazol-1-yl)ethanone (10.24g) with the anion derived from propionitrile according to the method of Example 10(i) gave a crude product which was chromatographed on silica gel. Elution with ether/ethyl acetate (7:3) followed by

combination and evaporation of the relevant fractions gave the less polar enantiomeric pair of the title compound (2.1g), m.p. 164°C.

Further elution gave the more polar enantiomeric pair of the title compound (0.259g), m.p. 188°C.

(ϋ) 2-(2,4-Dichlorophenyl)-3-(tetrazol-5-yl)-1-(1H-1,2,4- triazol-1-yl)butan-2-ol

A mixture of the less polar enantiomeric pair obtained in part (i) (2.07g) and tri-n-butyltin azide (3.15g) was heated at 170°C for 3 hours. The reaction mixture was cooled to about 70°C, diluted with ethyl acetate and the solution was cooled to room temperature. A concentrated solution of ethereal hydrogen chloride was added to destroy residual azide and the resulting solid was filtered off and dried to give the title compound as a single enantiomeric pair, (2.1g), m.p. 240°C.

Analysis %:-

Found: C, 44.08; H, 3.76; N, 27.79

C₁₃H₁₃Cl₂N₇O requires: C, 44.07; H, 3.67; N, 27.68 (iii) 2-(2,4-Dichlorophenyl)-1-(1H-1,2,4-triazol-1-yl)-3- (5-trifluoromethyl-1,3,4-oxadiazol-2-yl)butan-2-ol

Dicyclchexylcarbodiimide (206mg) and trifluoroacetic acid

(0.15 ml) were added to a stirred suspension of the product of part (ii) (354 mg) in dry xylene (20 ml). The mixture was heated at reflux for 4 hours and then further

dicyclchexylcarbodiimide (206 mg) and trifluoroacetic acid

(0.15 ml) were added. Heating was continued for 16 hours and then the mixture was evaporated. The residue was chromatographed on silica gel using ethyl acetate/hexane

(1:1) as eluent. Combination and evaporation of the relevant fractions, followed by trituration of the residue with a mixture of ether and hexane, gave the title compound as a single enanticmeric pair, (74 mg), m.p. 140°C.

Analysis %:-

Found: C, 43.17; H, 2.99; N, 16.28

C₁₅H₁₂Cl₂F₃N₅O₂ requires: C, 42.67; H, 2.87; N, 16.59

Activity date

The in vitro antifungal activities of a selection of the compounds of the formula (I) were determined by the method outlined on page 23 of the description.

Claims

1. A compound of the formula:-

or a pharmaceutically acceptable salt thereof,

wherein R is phenyl cptionally substituted by 1 to 3

substituents each independently selected from halo and CF₃;

R¹ is C₁-C₄ alkyl; R² is H or C₁-C₄ alkyl; and

"Het" is oxazol-2-yl, thiazol-2-yl,

1,2,4-oxadiazol-3 or 5-yl, 1,2,4-thiadiazol-5-yl, 1,3,4-oxadiazol-2-yl or 1,3,4-thiadiazol-2-yl, all of which may be optionally substituted by C₁-C₄ alkyl or CF₃. 2. A compound as claimed in claim 1 wherein R is phenyl

substituted by 1 or 2 halo substituents.

3. A compound as claimed in claim 2 wherein R is phenyl

substituted by 1 or 2 substituents each independently selected from fluoro and chloro.

4. A compound as claimed in claim 3 wherein R is

2-fluorophenyl, 2-chlorophenyl, 2,4-difluorophenyl or

2,4-dichlorophenyl. 5. A compound as claimed in any preceding claim wherein R¹ is C₁-C₄ alkyl and R² is H.

A compound as claimed in claim 5 wherein R¹ is methyl.

7. A compound as claimed in any preceding claim wherein

"Het" is oxazol-2-yl, thiazol-2-yl, 1,2,4-oxadiazol-3 or 5-yl, 1,3,4-oxadiazol-2-yl or 1,3,4-thiadiazol-2-yl, all of which may be optionally substituted by one C₁-C₄ alkyl or CF substituent.

8. A compound as claimed in claim 7 wherein

"Het" is oxazol-2-yl, thiazol-2-yl,

5-methyl-1,2,4-oxadiazol-3-yl,

3-methyl-1,2,4-oxadiazol-5-yl, 1,3,4-oxadiazol-2-yl,

5-methyl-1,3,4-oxadiazol-2-yl,

5-trifluoromethyl-1,3,4-oxadiazol-2-yl or

1,3,4-thiadiazol-2-yl.

9. A compound as claimed in claim 8 wherein

"Het" is 1,3,4-oxadiazol-2-yl or 1,3,4-thiadiazol-2-yl.

10. 2-(2-Chlorophenyl)-3-(1,3,4-oxadiazol-2-yl)-1-(1H-1,2,4- triazol-1-yl)butan-2-ol or 2-(2-chlorophenyl)-3-(1,3,4- thiadiazol-2-yl)-1-(1H-1,2,4-triazol-1-yl)butan-2-ol, or a paharmaceutically acceptable salt thereof.

11. A pharmaceutical composition comprising a compound of the formula (I) or a pharmaceutically acceptable salt thereof, as claimed in any preceding claim, together with a pharmaceutically acceptable diluent or carrier.

12. A compound of the formula (I) or a pharmaceutically

acceptable salt or composition thereof, as claimed in any one of claims 1 to 10 and 11 respectively, for use as a medicament.

13. The use of a compound of the formula (I) or of a

pharmaceutically acceptable salt or composition thereof, as claimed in any one of claims 1 to 10 and 11 respectively, for the manufacture of a medicament for the curative or prophylactic treatment of a fungal infection.

14. A compound of the formula:-

,

, or

,

wherein R, R¹ and R² are as defined in claim 1, R⁷ is H,

C₁-C₄ alkyl or CF_3, R⁸ is C₁-C₄ alkyl and R¹⁰ is H, C₁-C₄ alkyl or CF₃.

15. A process for the preparation of a compound of the formula:-

or a pharmaceutically acceptable salt thereof, wherein R is phenyl cptionally substituted by 1 to 3 substituents each independently selected from halo and CF₃ ;

R¹ is C₁-C₄ alkyl;

R² is H or C₁-C₄ alkyl; and "Het" is a) 5-substituted-oxazol-2-yl,

4,5-disubstituted-oxazol-2-yl,

5-substituted-thiazol-2-yl,

4,5-disubstituted-thiazol-2-yl, cptionally substituted 1,2,4-thiadiazol-5-yl or substituted

1,3,4-thiadiazol-2-yl, wherein the "Het" substituents are each independently selected from C₁-C₄ alkyl and CF₃, which comprises reacting a 1'-deprotonated form of a compound of the formula:-

R ¹R²CH-Het ....(II) wherein * represents the 1' position and R¹,R² and

"Het" are as previously defined for this part (a), with a ccsipound of the formula:-

wherein R is as previously defined for this part (a); oxazol-2-yl, 4-substituted-oxazol-2-yl, thiazol-2-yl or 4-substituted-thiazol-2-yl,

wherein the "Het" substituent is C₁-C₄ alkyl or CF₃, which comprises deproteoting a compound of the formula:-

,

wherein R, R¹ and R² are as previously defined for this part (b) , X is O or S, Y is CH, C(C₁-C₄ alkyl) or

C(CF₃) and Z is a protecting group; c) 1,2,4-αxadiazol-5-yl cptionally substituted by a C₁-C₄ alkyl or CF₃ substituent, which comprises

intramolecular condensation of a compound of the formula:-

wherein R, R¹ and R² are as previously defined for this part (c) and R³ is H, C₁-C₄ alkyl or CF₃; d) 1,2,4-oxadiazol-3-yl cptionally substituted by a C₁-C₄ alkyl or CF₃ substituent, which comprises

intramolecular condensation of a compound of the formula:-

wherein R, R¹ and R² are as previously defined for this part (d) and R⁸ is H, C₁-C₄ alkyl or CF₃; e) 1,3,4-oxadiazol-2-yl optionally substituted by a C₁-C₄ alkyl or CF₃ substituent, which comprises heating at above room temperature a compound of the formula:-

wherein R, R¹ and R² are as previously defined for this part (e) and R⁷ is H, C₁-C₄ alkyl or CF₃; f) 1,3,4-oxadiazol-2-yl, which comprises heating at above room teπperature a compound of the formula:-

wherein R, R¹ and R² are as previously defined for this part (f) and R⁸ is C₁-C₄ alkyl; 1, 3 , 4-oxadiazol-2-yl substituted by a C₁ -C₄ alkyl or CF₃ substituent, which comprises heating at above room temperature a ccsipound of the formula:-

wherein R, R¹ and R² are as defined for this part (g) and R⁹ is C₁-C₄ alkyl or CF₃; or h) 1,3,4-thiadiazol-2-yl cptionally substituted by a C₁-C₄ alkyl or CF₃ substituent, which comprises treatment of a compound of the formula:-

wherein R, R¹ and R² are as defined for this part (h) and R¹⁰ is H, C₁-C₄ alkyl or CF , with acid: any one of said processes (a) to (h) being optionally followed by conversion of the compound of the formula (I) to a pharmaceutically acceptable salt thereof.

16. A process as claimed in claim 15, part (a) in which the

1'-deprotonated form of the compound of the formula (II) is a lithium, sodium or potassium salt thereof and the reaction is carried out at from -80 to 0°C.

17. A process as claimed in claim 15, part (b) in which Z is tri(C₁-C₄ alkyl)silyl and the deprotection is carried out using a source of fluoride ions.

18. A process as claimed in claim 15, part (c) or claim 15, part (d) in which the condensation is carried out by heating the compound at from 130° to 180°C.

19. A process as claimed in claim 15, part (h) in which the

acid used is dichloroacetic acid.

20. A process as claimed in claim 15 wherein

R is phenyl substituted by 1 or 2 halo substituents;

R¹ is C₁-C₄ alkyl, R² is H and

"Het" is oxazol-2-yl, thiazol-2-yl, 1,2,4-oxadiazol-3 or

5-yl, 1,3,4-oxadiazol-2-yl or 1,3,4-thiadiazol-2-yl, all of which may be optionally substituted by one C₁-C₄ alkyl or

CF₃ substituent.

21. A process as claimed in claim 20 wherein R is phenyl

22. A process as claimed in claim 21 wherein R is

2-fluorophenyl, 2-chlorophenyl, 2,4-difluorophenyl or

2,4-dichlorophenyl;

R is methyl; and

"Het" is oxazol-2-yl, thiazol-2-yl,

5-methyl-1,2,4-oxadiazol-3-yl,

3-methyl-1,2,4-oxadiazol-5-yl, 1,3,4-oxadiazol-2-yl,

5-methyl-1,3,4-oxadiazol-2-yl,

5-trifluoromethyl-1,3,4-oxadiazol-2-yl or

1,3,4-thiadiazol-2-yl.

23. A process as claimed in claim 22 wherein R is 2-chlorophenyl and

"Het" is 1,3,4-oxadiazol-2-yl or 1,3,4-thiadiazol-2-yl.

24. A method of treatment of an animal, including a human being, to cure or prevent a fungal infection which comprises treating said animal with an effective amount of a compound of the formula (I), or with a pharmaceutically acceptable salt or composition thereof, as claimed in any one of claims 1 to 10 and 11 respectively.