WO1993017034A1

WO1993017034A1 - Amphotericin b derivatives

Info

Publication number: WO1993017034A1
Application number: PCT/GB1993/000306
Authority: WO
Inventors: Colin Thomas Shanks
Original assignee: Smithkline Beecham Plc
Priority date: 1992-02-19
Filing date: 1993-02-12
Publication date: 1993-09-02
Also published as: GB9203476D0; AU3461793A

Abstract

A compound of formula (I) or a pharmaceutically acceptable salt thereof: wherein R1 is a group CO.N(R5)OR6 in which R5 is hydrogen, C1-6 alkyl, C3-6 alkenyl, C3-6 cycloalkyl, C3-6 cycloalkyl-C1-6 alkyl, aryl C1-6 alkyl, heteroaryl C1-6 alkyl, aryl, heteroaryl in which any aryl or heteroaryl moiety is optionally substituted, R6 is hydrogen, C1-6 alkyl, C3-6 alkenyl, C3-6 cycloalkyl, C3-6 cycloalkyl-C1-6 alkyl, aryl C1-6 alkyl, heteroaryl C1-6 alkyl, aryl, heteroaryl, in which any aryl or heteroaryl moiety is optionally substituted, C2-6 hydroxyalkyl, a group (CH2)nNR7R8 in which n = 2 to 6, R7 and R8 independently represent hydrogen or C1-6 alkyl or together with the nitrogen to which they are attached from a group of formula (i); in which s and r together represent 3, 4 or 5 and X represents oxygen, sulphur CH2, or NR in which R is hydrogen or C1-6 alkyl; or R6 is a group of formula (ii); in which t is 1 to 6 and R9 is hydrogen, C1-6 alkyl or C3-6 alkenyl; or R6 is a group of formula (iii); in which u is 1 to 6 and R10 and R11 independently represent hydrogen, or C1-6 alkyl; R2 is hydroxy or C1-6 alkoxy; R3 is amino or a derivative thereof; and R4 is hydrogen or hydroxy; or R2 and R4 together represent a bond.

Description

AMPHOTERICIN B DERIVATIVES

The present invention relates to novel compounds, their preparation and their use in the treatment of fungal infections in animals, including humans.

The polyene macrolide amphotericin B, produced by Streptomyces nodosus, is widely used for the treatment of fungal infections.

Amphotericin B is the only complex polyene macrolide whose molecular structure and absolute configuration have been firmly established by x-ray crystallographic analysis. Amphotericin B has the formula (A):

Derivatives of amphotericin B have now been prepared which have novel substituents at the 16-position and which derivatives have been shown to have anti-fungal activity and have potential utility as anti-fungal agents.

Accordingly, the present invention provides a compound of formula (I) or a pharmaceutically acceptable salt thereof:

wherein R₁ is a group CO.N(R₅)OR₆ in which R₅ is hydrogen, C_1-6 alkyl, C_3-6 alkenyl, C_3-6 cycloalkyl, C_3-6 cycloalkyl -C_1-6 alkyl, aryl C_1-6 alkyl, heteroaryl C_1-6 alkyl, aryl, heteroaryl in which any aryl or heteroaryl moiety is optionally substituted,

R₆ is hydrogen, C_1-6 alkyl, C_3-6 alkenyl, C_3-6 cycloalkyl, C_3-6 cycloalkyl -C_1-6 alkyl, aryl C_1-6 alkyl, heteroaryl C_1-6 alkyl, aryl, heteroaryl, in which any aryl or heteroaryl moiety is optionally substituted, C_2-6 hydroxyalkyl, a group (CH₂)_nNR₇R₈ in which n = 2 to 6, R₇ and R₈ independently represent hydrogen or C_1-6 alkyl or together with the nitrogen to which they are attached from a group of formula (i);

in which s and r together represent 3, 4 or 5 and X represents oxygen, sulphur CH₂, or NR in which R is hydrogen or C_1-6 alkyl;

or R₆ is a group of formula (ii);

in which t is 1 to 6 and R₉ is hydrogen, C_1-6 alkyl or C_3-6 alkenyl;

or R₆ is a group of formula (iii);

in which u is 1 to 6 and R₁₀ and R₁₁ independently represent hydrogen, or C_1-6 alkyl;

R₂ is hydroxy or C_1-6 alkoxy; R₃ is amino or a derivative thereof;

and R₄ is hydrogen or hydroxy; or R₂ and R₄ together represent a bond.

It should be appreciated that for compounds of formula (I) in which R₅ and/or R₆ is C_3-6 alkenyl the double bond is not in the C_1-2 position.

Unless otherwise specified, an alkyl moiety or group or an alkenyl group preferably has from 1 to 6 carbon atoms, more preferably 1 to 4 carbon atoms and may be straight-chain or branched.

When used herein, the term aryl includes aromatic carbocyclic groups such as phenyl and naphthyl, preferably phenyl.

The term heteroaryl includes 5- or 6- membered monocyclic and 9- or 10-membered bicyclic heteroaryl.

In addition, 5- or 6- membered monocyclic and 9- or 10- membered bicyclic heteroaryl preferably contain one or two heteroatoms selected from nitrogen, oxygen and sulphur which in the case of there being more than one heteroatom may be the same or different. When 9- or 10- membered bicyclic heteroaryl, the two rings are fused, preferably with one 5- or 6-membered ring containing a single heteroatom.

Optional substituents for alkyl, alkenyl, arylC_1-8 alkyl, aryl and heteroaryl groups may be selected from OH, C_1-6 alkyl, C_1-6 alkoxy, carboxy, nitro, halogen, and amino optionally substituted by C_1-6 alkyl, C_1-6 acyl or aryl. R₅ in the variable R₁ is preferably hydrogen or methyl.

R₆ in the variable R₁ is preferably hydrogen, methyl, prop-2-enyl, hydroxyethyl or N-ethylmorpholino. R₂ is preferably hydroxy and R₄ is preferably hydrogen.

Suitably R₃ is primary amino.

Also included within the scope of compounds in which R₃ is an amine group or derivative thereof include acyl derivatives bearing a basic substituent such as N-D-lysyl and N-D-ornithyl derivatives, guanidine derivatives, and N-glycosyl derivatives. The preparation of further amino group derivatives is described in European Patent Publication 0 010 297 (Schering), European Patent Publication 0 031722 (Dumex) US 4 195 172 and European Patent Publication O 428440.

The term pharmaceutically acceptable salt encompasses solvates and hydrates. Thus where compounds of formula (I) or pharmaceutically acceptable salts thereof form solvates or hydrates, these also form an aspect of the invention.

The compounds of formula (I) wherein R₃ is hydrogen can form acid addition salts with acids, such as conventional pharmaceutically acceptable acids, for example hydrochloric, hydrobromic, phosphoric, acetic, fumaric, salicylic, citric, lactic, mandelic, tartaric, oxalic, methanesulphonic, aspartic and ascorbic. The invention also extends to quaternary salts. The present invention also provides a process for the preparation of compounds of formula (I) which process comprises the reaction of a compound of formula (II):

wherein R₂ is hydroxy or C_1-6 alkoxy, R₃' is an amine protecting group and R₄ is hydrogen or hydroxy or R₂ and R₄ together represent a bond and each R₁₂ is hydrogen or a silyl protecting group; with a compound of formula (III) or, an acid addition salt thereof; in the presence of an amide coupling reagent;

wherein R₅ is as defined in relation to formula (I) and R₆' is R₆ as defined in relation to formula (I) or a group convertible thereto, and thereafter optionally or as necessary in any appropriate order, converting R₆' when other than R₆ to R₆, converting NHR₃' to R₃, removing the R₁₂ silyl protecting groups, interconverting R₂ and R₄, and forming a

pharmaceutically acceptable salt. When R₆' is alkyl, the reaction between a compound of formula (II) and formula (III) is suitably carried out in an inert solvent such as

dimethylformamide at ambient temperature in the presence of a buffer such as sodiuim acetate or a base such as pyridine and further in the presence of dicyclohexylcarbodiimide (DCCI) as the amide coupling reagent.

When R₆' is other than alkyl, the reaction between a compound of formula (II) and formula (III) is suitably carried out in an inert solvent such as dimethylformamide in the presence of a base such as N,N-di-isopropylethylamine and in the presence of bromo-tris-pyrrolidinophosphonium-hexafluoro-phosphate as the amide coupling reagent.

Addition salts of the compound of formula (III) include the hydrochloric and hydrobromic salt thereof. Preferably the acid addition salt is the hydrochloric salt thereof.

Values for R₆' when a group convertible to R₆ include conventional protecting groups which may be converted to R₆ using conventional deprotection methods such as those described in Greene, T.W. 'Protective groups in Organic Synthesis' New York, Wiley (1981). Preferably when R₆ is hydrogen a suitable group convertible to R₆ is hydrogen is a silyl protected group such as i-butyldimethyl silyl which may be converted to a hydrogen by treatment with a salt of a strong acid and a weak base such as pyridinium para-toluene sulphate in a suitable solvent such as a water/THF mixture.

It should be appreciated that when R₂ is alkoxy and R₄ is hydrogen this reaction converts the alkoxy function to R₂ is hydroxy and this is an example of interconversion of R₂ from alkoxy to hydroxy. R₃' amine protection groups are chosen such that they are readily removable subsequent to the initial reaction between a compound of formula (II) and a comound of formula (III) or an acid addition salt thereof to provide a compound of formula (I) in which R₃ is hydrogen.

Values for R₃' include trifluoracetyl, 9-fluorenylmethoxycarbonyl, trichloroethoxycarbonyl, 2-methylsulphonylethoxycarbonyl

2-trimethylsilylethoxycarbonyl and allyloxycarbonyl.

Preferably R₃' is 9-fluorenylmethoxycarbonyl.

Suitable R₁₂ silyl protecting groups include trimethylsilyl, triethylsilyl andt-butyldimethylsilyl.

Preferably R₁₂ is triethylsilyl.

An R₂ hydroxy function can be converted to an alkoxy function using procedures analogous to those outlined in WO/91/0947.

Interconversion of R₄ can be carried out according to the procedures outlined in EP-A-0431874 (Beecham Group p.l.c.). Where R₃ in compounds of formula (I) is primary amine the removal of an R₃' amine protecting group to give an R₃ primary amine may be carried out under basic conditions.

An R₃' amine protection group, such as 9-fluorenylmethoxycarbonyl, may be removed under basic conditions in a solvent such as methanolic dimethyl sulphoxide. Suitable bases for amine deprotection include ammonia, dialkylamines such as dimethylamine and diethylamine, trial-kylamines such as triethylamine, cyclic amines and especially cyclic secondary amines such as morpholine, piperazine and more especially piperidine, and diazabicyclic bases such as

1,5-diazabicyclo[4.3.0]non-5-ene (DBN) and preferably

1,8-diazabicyclo[5.4.0]undec-7-ene (DBU). The deprotection may be carried out using from 1-10 equivalents of base, preferably from 1-2 equivalents, at reduced or elevated temperatures, for example from -30°C to 50°C and preferably from 0°C to room temperature, over a time period ranging from 1 minute to 5 hours and preferably from 30 minutes to 2.5 hours.

R₁₂ silyl protecting groups in compounds of formula (II) may be removed using known deprotection methods, for example using a solution of hydrogen fluoride-pyridine in tetrahydrofuran or

tetrahydrofuran/methanol mixtures at normal or reduced temperature, for example from -10°C to 50°C and preferably from 0°C to room

temperature, over a time period up to 60 hours and preferably from 4 to 24 hours.

Intermediate compounds of formula (II) in which R₄ is hydrogen and R₂ is alkoxy may be prepared from amphotericin B according to the procedures outlined in WO 91/09047 (Beecham Group p.l.c).

It should be appreciated that the compound wherein R₂ is hydroxy and R₃ and R₄ are hydrogen is amphotericin B itself, which is commercially available.

Intermediate compounds of formula (II) in which R₂ is hydroxy or alkoxy and R₄ is hydroxy may be prepared according to procedures outlined in EP-A-0431874 (Beecham Group p.l.c).

Intermediate compounds of formula (II) in which R₂ and R₄ together represent a bond may be prepared according to the procedures outlined in EP-A-0 350 184. Compounds of formula (III) are either commercially available or may be prepared by conventional methods known in the art of hydroxylamine chemistry, such as those described by E Grochowski, Synthesis, (1976) p.682. The 13-position anomeric hydroxyl group maybe selectively exchanged using the appropriate C_1-6 alkyl alcohol in the presence of an acid catalyst such as 10-camphorsulphonic acid or pyridinium p-toluene sulphonate under anhydrous conditions. The reaction may be carried out in an inert solvent such as tetrahydrofuran and the alcohol may act either wholly or partially as the solvent. The reaction is conveniently carried out in the presence of an H₂O-scavenger such as molecular sieves and/or under an inert atmosphere. R₃' amine protection groups may be introduced by standard procedures. For example, an R₃' trifluoroacetyl amine protection group may be introduced by reaction of the primary amine with ethyl trifluoroacetate in the presence of base such as diisopropylethylamine, in a

methanol-dimethyl sulphoxide or methanol- dimethylformamide solvent mixture at reduced to normal temperatures, for example at 0°C.

An R₃' 9-fiuorenylmethoxycarbonyl amine protection group may be introduced by addition of 9-fluorenylmethyl chloroformate to a solution of the primary amine in methanol-dimethylformamide under anhydrous conditions, in the presence of a base such as potassium carbonate.

Alternatively an R₃' 9-fluorenylmethoxycarbonyl group maybe introduced by addition of N-(9-fluorenylnιethoxycarbonyloxy)sucdnimide to a slurry of the primary amine in rnethanol-diniethylformamide under anhydrous conditions in the presence of a base such as pyridine.

Free hydroxyl groups may be silylated using standard procedures. The reaction with silyating agents such as trimethylsilyl

trifluoromethanesulphonate and triethylsilyl trifluoromethanesulphonate may be carried out in an inert solvent, for example dichloromethane, hexane or diethyl ether, under an inert atmosphere at ambient or reduced temperatures, for example from 0°C to 25°C. The reaction is conveniently effected using an excess of the silylating agent in the presence of a base, for example a pyridine derivative such as 2,6-lutidine. Alternatively, when a liquid, the base may replace the solvent. The reaction time is dependent on the size of the silyl group, ranging from a few minutes for a trimethylsilyl group to several hours for larger silyl groups. The compounds of the formula (I) and their pharmaceutically acceptable salts are anti-fungal agents, potentially useful in combating fungal infections in animals, including humans. For example they are

potentially 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 may also be used in the treatment of systemic fungal infections caused by, for example Candida albicans. Cryotococcus neoformans, Aspergillus fumigatus, Coccidioides, Paracoccidioides, Histoplasma or Blastomyces spp. They may also be of use in treating eumycotic mycetoma, chromoblastomycosis, and

phycomycosis. 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 composition is preferably for human use in tablet, capsule, injectable or cream form.

For human use, the antifungal compounds of the formula (I) or

pharmaceutically acceptable salts thereof 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 may be administered orally in the form of a tablet containing such excipients as starch or lactose, or in a capsule or ovule either alone or in admixture with excipients, or in the form of an elixir or suspension containing a flavouring or colouring agent. They may 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. For oral and parenteral administration to human patients, it is expected that the daily dosage level of the antifungal compounds of the formula (I) will be from 0.1 to 1 mg/kg (in divided doses) when administered by either the oral or parenteral route. Thus tablets or capsules of the compounds can be expected to contain from 5 mg to 0.5 g of active compound 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 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 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 maybe required.

Within the indicated dose range, no adverse toxicological effects have been observed with the compounds of the invention which would preclude their administration to suitable patients for the treatment of fungal infections.

The present invention further provides a compound of formula (I) or a pharmaceutically acceptable salt thereof for use as an active therapeutic substance.

A compound for use as an active therapeutic substance is intended for use in the treatment of disorders in animals including humans. As stated above, compounds of formula (I) and their pharmaceutically acceptable salts have anti-fungal activity and are potentially useful in combating fungal infections in animals including humans.

Accordingly the present invention further provides a compound of formula (I) or a pharmaceutically acceptable salt thereof for use in the treatment of fungal infections.

The present invention additionally provides a method of treatment of fungal infections in animals, including humans, which comprises administering an effective anti-fungal amount of a compound of formula

(I) or a pharmaceutically acceptable salt thereof to the animal.

The present invention also provides the use of a compound of formula (I) or a pharmaceutically acceptable salt thereof for the manufacture of a medicament for use in the treatment of fungal infections in animals, including humans.

The following Examples illustrate the preparation of compounds of the invention and the following Descriptions illustrate the preparation of intermediates thereto.

Description 1 N-(9-Fluorenylmethoxycarbonyl)-13-O-methyl amphotericin B 16-(N-methoxy)carboxamide (D1)

To N-(9-fluorenylmethoxycarbonyI)-13-O-methyl amphotericin B (0.58g, 0.5mmol) dissolved in dry -N,N-dimethylformamide (2.5mL) under nitrogen was added successively dry pyridine (2mL), methoxylamine hydrochloride (0.16g, 1.95mmol) and 1,3-dicyclohexylcarbodiimide (0.50g, 2.42mmol) and the mixture stirred in a sealed flask for 7 hours. The solution was added to diethyl ether (2L), the precipitate filtered and washed with water (100mL), ethyl acetate (200mL) and diethyl ether (200mL). The residue was purified by chromatography on silica, eluting with methylene chloride: methanol (7:1) to give the title product (D1) (0.20g). λmax (MeOH) 406 (ε 148262), 383 (ε 135907), 364 (ε 82091) nm. ʋmax (KBr) 3430, 1704 cm^-1. δ ¹H (400 MHz) (CD₃OD:C₅D₅N; 1:1). Characteristic signals include:- 1.15 (3H, d, J7.12 Hz), 1.24 (3H, d, J6.59 Hz), 1.35 (3H, d, J6.35 Hz), 1.47 (3H, d, J6.02 Hz), 3.25 (3H, s), 3.90 (3H, s), 4.80 (1H, multiplet), 4.84 (1H, s), 5.47 (1H, multiplet), 5.63 (1H, dd, J14.1 and 9.63 Hz), 6.14 (1H, dd, J14.24 and 6.84 Hz), 6.23-6.61 (12H, complex), 7.30 (2H, t, J7.45 Hz), 7.42 (2H, t, J7.4 Hz), 7.71 (2H, t, J7.08 Hz) and 7.83 (2H, d, J7.51 Hz) ppm. δ¹³C (68 MHz) (CD₃OD: C₅D₅N; 1:1) 12.42, 17.72, 18.58, 18.97, 30.62, 36.19, 38.25, 41.65, 41.92, 42.95, 43.36, 43.70, 44.86, 47.87, 48.49, 54.87, 58.27, 64.37, 66.10, 67.36, 67.72, 68.40, 71.05, 71.47, 71.93, 74.61, 74.88, 75.66, 76.53, 78.43, 99.76, 102.10, 120.72, 126.15, 127.90, 128.48, 130.38, 132.44-134.76(m), 137.64, 142.08, 144.96, 145.08, 158.17, 170.68, 171.96.

Mass spectrum (FAB: Thiodiethanol-Na matrix). Found: MNa⁺, 1211.5. C₆₄H₈₈N₂O₁₉ requires M, 1188.6. Description 2 N-(9-Fluorenylmethoxycarbonyl) amphotericin B 16-(N-methoxy)carboxamide (D2)

To a solution of N-(9-fluorenylmethoxycarbonyl)-13-O-methyl

amphotericin B 16-(N-methoxy)carboxamide (0.183g, 0.154mmol) in tetrahydrofuran-water (6:1, 7mL) under nitrogen was added pyridinium p-toluenesulphonate (0.292g, 1.16mmol). After stirring in a sealed flask for 1.5 hours triethylamine (0.23mL, 0.167g, 1.65mmol) was added, and the mixture poured into diethyl ether (1L). The precipitate was filtered and washed with diethyl ether (500mL), dry distilled tetrahydrofuran (50ml) then diethyl ether (500mL). The solid was dried in vacuo giving the title product (D2) (0.115g). λmax (MeOH) 406 (ε136164), 382 (ε124796), 363 (ε75606) nm. ʋmax (KBr) 3428, 1717, 1650cm^-1. δ ¹H (400 MHz) [CD₃OD: (CD₃)₂SO; 1:3]. Characteristic signals include:- 0.95 (3H, d, J7.07 Hz), 1.06 (3H, d, J6.5 Hz), 1.15 (3H, d, J6.3 Hz), 1.21 (3H, d, J4.12 Hz), 3.61 (3H, s), 4.49 (2H, multiplet), 5.03 (1H, multiplet), 5.59 (1H, dd, J14.41 and 9.22 Hz), 5.91 (1H, dd, J14.13 and 6.42 Hz), 6.05-6.45 (12H, complex), 7.35 (2H, t, J7.4 Hz), 7.42 (2H, t, J7.38 Hz), 7.76 (2H, d, J7.09 Hz), and 7.88 (2H, d, J7.5 Hz) ppm. δ¹³C (68 MHz) [CD₃)₂SO; 1:3] 12.09, 17.01, 18.14, 18.53, 29.33, 35.24, 37.13, 39.90, 40.11, 42.17, 42.62, 44.68, 46.39, 46.95, 53.91, 56.96, 63.43, 64.40, 65.41, 65.91, 66.55, 67.85, 69.18, 69.49, 69.63, 69.88, 73.48, 73.78, 73.97, 75.45, 77.36, 97.26, 97.52, 120.16, 125.55, 125.64, 127.26, 127.78, 129.00, 131.49-134.08(m), 136.98, 140.94, 144.15, 144.20, 156.12, 168.90, 170.81.

Mass spectrum (FAB: Thiodiethanol-Na matrix). Found: MNa⁺, 1197.5. C₆₃H₈₆N₂O₁₉ requires M, 1174.5. Description 3 N-(9-Fluorenylmethoxycarbonyl)-13-O-methyl amphotericin B 16-(N-tert-butyldimethylsilyloxy)carboxamide (D3)

To a solution of N-(9-Fluorenylmethoxycarbonyl)-13-O-methyl

amphotericin B (0.29g, 0.25mmol) in dry N,N-dimethyflformamide (2mL) under nitrogen was added successively N,N-diiopropylethylamine (0.15ml, 0.111g, 0.86mmol), O-(tert-butyldimethylsilyl) hydroxylamine (0.038g, 0.25mmol) and bromo-trispyrrolidino-phosphonium hexafluorophosphate [PyBroP] (0.12g, 0.25mmol) and the mixture stirred in a sealed flask for 3 hours. The solution was concentrated in vacuo, the residue purified by chromatography on silica, eluting with methylene chloride: methanol (9:1), giving the title product (D1) (0.21g). λmax (MeOH) 406 (ε 134209), 383 (ε 125193), 364 (ε 76636) nm. ʋmax (KBr) 3428, 1706cm^-1. δ¹H (400 MHz) [CD₃OD: (CD₃OD: (CD₃)₂SO; 1:3]. Characteristic signals include:- 0.15 (3H, s), 0.16 (3H, s), 0.94 (12H, complex), 1.05 (3H, d, J6.45 Hz), 1.14 (3H, d, J6.45 Hz), 1.18 (3H, d, J6.10 Hz), 2.30 (1H, multiplet), 3.08 (3H, s), 3.60 (1H, multiplet), 4.46 (1H, s), 4.50 (1H, multiplet), 5.04 (1H, multiplet), 5.58 (1H, dd, J14.83 and 9.67 Hz), 5.87 (1H, dd, J14.19 and 7.09 Hz), 6.04-6.45 (12H, complex), 7.34 (2H, t, J7.43 Hz), 7.41 (2H, t, J7.35 Hz), 7.74 (2H, multiplet), and 7.86 (2H, d, 7.60 Hz) ppm. δ¹³C (68 MHz) [CD₃OD: (CD₃)₂SO; 1:3] -5.20, 05.15, 11.90, 17.66, 18.19, 18.53, 25.91, 28.98, 34.97, 37.17, 41.0, 41.4, 42.7, 42.8, 43.1, 44.5, 47.29, 48.10, 53.47, 57.32, 65.29, 66.03, 66.25, 66.55, 66.80, 69.89, 70.00, 70.16, 70.48, 73.14, 73.77, 74.28, 76.14, 96.56, 100.96, 120.36, 125.76, 127.49, 128.02, 128.58, 131.07-134.07 (m), 137.40, 141.28, 144.45, 156.53, 169.79, 170.88.

Mass spectrum (FAB: Thiodiethanol-Na matrix). Found: MNa⁺, 1311.5. C₆₉H₁₀₀N₂O₁₉ requires m, 1288.6. Description 4 N-(9-Fluorenylmethoxycarbonyl) amphotericin B 16-(N-hydroxy) carboxamide (D4)

To N-(9-fluorenylmethoxycarbonyl)-13-O-methyl amphotericin B 16-(N- tert-butyldimethylsilyloxy) carboxamide (0.197g, 0.153mmol) dissolved in tetrahydrofuran: water (6:1, 5.25 mL) was added pyridinium p-toluenesulphonate (0.322g, 1.282 mmol). After stirring for 2 hours, under nitrogen in a sealed flask, triethylamine (0.26 mL, 188 mg, 1.859 mmol) was added and the solution poured into diethyl ether (1L). The

precipitate was filtered, the solid washed with water (50mL),

tetrahydrofuran: water (4:3, 15 mL) and diethyl ether (200 mL). Drying in vacuo gave the title product (D4) (0.081g). λmax (MeOH) 407 (ε 105767), 384 (ε 99729), 364 (ε 62113) nm. ʋmax (KBr) 3432 cm^-1. δ¹H (400 MHz) [CD₃OD: (CD₃)₂SO; 1:3]. Characteristic signals include:- 0.94 (3H, d, J7.07 Hz), 1.06 (3H, d, J6.47 Hz), 1.14 (3H, d, J6.31 Hz), 1.18 (3H, d, J5.43 Hz), 2.30 (1H, multiplet), 3.59 (1H, multiplet), 4.38 (1H, multiplet), 4.48 (1H, s), 5.26 (1H, multiplet), 5.42 (1H, dd, J14 and 10 Hz), 5.98 (1H, dd, J15.05 and 8.70 Hz), 6.12-6.50 (12H, complex), 7.33 (2H, multiplet), 7.41 (2H, t, J7.4 Hz), 7.74 (2H, multiplet) and 7.86 (2H, d, J7.5 Hz) ppm. δ¹³C (68 MHz) [CD₃OD: (CD₃)₂SO; 1:3] 12.18, 17.10, 18.25, 18.66, 29.77, 35.47, 37.66, 40.13, 42.32, 43.04, 44.69, 45.07, 47.21, 47.30, 54.23, 57.08, 97.51, 97.97, 120.32, 125.73, 127.46, 127.99, 129.17, 132.25-134.32 (m), 137.06, 137.52, 141.22, 144.42, 156.54, 169.22, 171.11.

Mass spectrum (FAB: Thiodiethanol - Na matrix). Found: MNa⁺, 1183.5. C₆₂H₈₅N₂O₁₉ require M, 1161.5. Description 5

N-(9-Fluorenylmethoxycarbonyl) amphotericin B 16-(N-n-prop-2-enyl-1-oxy) carboxamide (D5)

This intermediate was prepared from N-(9-fluorenylmethoxycarbonyl)-13-0-methyl amphotericin B and 0-allyl hydroxylamine in two steps by the methods outlined in descriptions 3 and 4. λmax (MeOH) 406, 382, 363nm. ʋmax (KBr) 3420, 1700cm^-1.

δ ¹H (400 MHz) [CD₃OD:(CD₃)₂SO, 1:5]. Characteristic signals include:- 0.94 (3H, d, J 7.1Hz), 1.05 (3H, d, J 6.3Hz), 1.13 (3H, d, J 6.4Hz), 1.18 (3H, d, J 5Hz), 3.70 (1H, d, J 2.8Hz), 4.43 (1H, s), 5.43 (1H, dd, J 10, MHz).

Mass spectrum (FAB: Thiodiethanol-Na matrix). Found: MNa⁺ 1223.5. C₆₅H₈₈N₂O₁₉ requires M, 1200.5.

Description 6

N-(9-Fluorenylmethoxycarbonyl) amphotericin B 16-(N-methoxy, N-methyl) carboxamide (D6)

To a solution of N-(9-fluorenylmethoxycarbonyl) amphotericin B (286 mg, 0.25 mmol) in N,N-dimethylformamide (2.5 ml) was added N,N- diisopropylethylamine (0.225 ml), N-O-dimethyl hydroxylamine

hydrochloride (24 mg, 0.25 mmol) and PyBroP (see description 3) (120 mg, 0.25 mmol). The mixture was stirred at room temperature for 3 hours and poured into diethyl ether (400 ml). The precipitate was filtered off, washed with water (25 ml) and ethyl acetate (100 ml), dried in vacuo and chromatographed on silica, eluting with methylene chloride:methanol (9:1) to give the title product (D6) (129 mg). λmax (MeOH) 408, 384, 365nm. ʋmax (KBr) 3425, 1717cm^-1.

δ¹H (400MHz) [CD₃OD:(CD₃)₂SO; 1:5]. Characteristic signals include:- 0.94 (3H, d, J 7.1Hz), 1.06 (3H, d, J 6.3Hz), 1.19 (3H, d, J 6.4Hz), 1.25 (3H, d, J 5.1Hz), 3.68 (1H, d, J 2.5Hz), 3.73 (3H, s), 5.43 (1H, dd, J 14.3, 10Hz), 5.96 (1H, dd, J 15.1, 8.8Hz). Mass spectrum (FAB: Thiodiethanol-Na matrix). Found: MNa⁺1211.

C₆₄H₈₈N₂O₁₉ requires M, 1188. Description 7

N-(2-t-Butyldimethylsilyloxy) ethoxyphthalmide (D7)

To a solution of 2-t-butyldimethylsilyloxy ethanol (7.04 g, 40 mmol), N-hydroxyphthalimide (6.53 g, 40 mmol) and triphenylphosphine (10.49 g, 40 mmol) in dry tetrahydrofuran (120 ml) at 0° was added, dropwise, diethylazodicarboxylate (7.16 ml, 45 mmol). The solution was stirred 24h, concentrated in vacuo and the residue triturated with ether. The solution was filtered and evaporated. The residue was chromatographed on silica, eluting with hexane:ethyl acetate (10:1) to give the title product (D7) (9.76 g). ʋmax (KBr) 1790, 1725cm^-1.

Mass spectrum (CI). Found: MH⁺ 322.

C₁₆H₂₃NO₄Si requires M, 321.

Description 8

2-(t-Butyldimethylsilyloxy) ethoxylamine (D8)

To a solution of N-(2-t-butyldimethylsilyloxy) ethoxyphthalimide (19.26 g, 60 mmol) in methylene chloride (250 ml) at 0° was added N- methylhydrazine (5.19 ml, 98.6 mmol) in methylene chloride (100 ml). After 2 hours at room temperature, solids were filtered off and the solution concentrated. The residue was taken up in ether, remaining solids being filtered off, and the ether evaporated to give crude product, purified by chromatography on silica, eluting with hexane: ethyl acetate (6:1) to give the title product (8.1 g). δ¹H (90MHz) [CDCl₃] 3.8 (4H, s), 5.5 (2H, s). Description 9

N-(9-Fluorenylmethoxycarbonyl) amphotericin B 16-[N-(2-t-butyldimethylsilyloxy) ethoxy] carboxamide (D9)

This material was prepared by the method of description 6.

λmax (MeOH) 406, 382, 363 nm. ʋmax (KBr) 3425 cm^-1.

δ¹H (400MHz) [CD₃OD: (CD₃)₂SO, 1:5]. Characteristic signals include:- 0.03 (6H, s), 0.85 (9H, s), 0.93 (3H, d, J 7.3Hz), 1.05 (3H, d, J 6.3Hz), 1.13 (3H, d, J 6.4Hz), 1.17 (3H, d, J 5.9Hz), 3.67 (1H, d, J 2.5Hz), 5.44 (1H, dd, J 10.1, 14.3Hz), 5.96 (1H, dd, J 15.0, 8.8Hz).

Mass spectrum (FAB: Thiodiethanol-Na matrix). Found: MNa⁺ 1341. C₇₀H₁₀₄N₂O₂₀Si requires M, 1318.

Description 10

N-(9-Fluorenylmethoxycarbonyl) amphotericin B 16-N-(2-hydroxyethoxy) carboxamide (D10)

To a solution of N-(9-fluorenylmethoxycarbonyl) amphotericin B 16-[N-(2-t-butyldimethylsilyloxy) ethoxy] carboxamide (0.66 g, 0.5 mmol) in tetrahydrofuran: dimethylformamide (10:1) (33 ml) was added tetra-n-butylammonium fluoride (0.24 g, 0.75 mmol) and the solution stirred at room temperature for 2 hours. The solution was poured into ether (1l) and the solid filtered and washed with water (200 ml), ethyl acetate (500 ml) and ether (500 ml). Chromatography on silica, eluting with methylene chloride:methanol (6:1) gave the title product (0.17 g). λmax (MeOH) 405, 382, 363 nm. ʋmax (KBr) 3415, 1700 cm^-1.

δ¹H (400 MHz) [(CD₃)₂SO: CD₃OD, 5:1]. Characteristic signals include:- 0.93 (3H, d, J 7.1Hz), 1.05 (3H, d, J 6.4Hz), 1.13 (3H, d, J 6.4Hz), 1.17 (3H, d, J 5.6Hz), 3.69 (1H, d, J 2.5Hz), 5.43 (1H, dd, J 14.3, 10.1Hz), 5.95 (1H, dd, J 15.1, 9.0Hz).

Mass spectrum (FAB: Thiodiethanol - Na matrix). Found : MNa⁺ 1227. C₆₄H₈₈N₂O₂₀ requires M, 1204. Description 11

N-[2-(4-Morpholino)] ethoxyphthalimide (D11) To a solution of N-hydroxyphthalimide (2.44 g, 15 mmol), N-(2-hydroxyethyl) morpholine (1.96 g, 15 mmol) and tri (p-methoxy phenyl) phosphine (5.26 g, 15 mmol) in tetrahydrofuran (75 ml) at 0° was added diisopropylazodicarboxylate (3.33 ml, 17 mmol), and the reaction stirred at room temperature for 3 days and concentrated in vacuo. Chromatography on silica, eluting with hexane: ethyl acetate (1:1) gave the title product (1.82 g). ʋmax (KBr) 1790, 1725 cm^-1.

Mass spectrum (CI). Found : MH⁺, 277.

C₁₄H₁₆N₂O₄ requires M, 276.

Description 12

2-(4-Morpholino) ethoxyamine (D12)

This material was prepared by the mehhod of description 8. ʋmax (film) 3300 cm^-1.

Mass spectrum (CI). Found : MH⁺ 147.

C₆H₁₄N₂O₂ requires M, 146.

Description 13

N-(9-Fluorenylmethoxycarbonyl) amphotericin B

16-N-[2-(4-morpholino) ethoxy] carboxamide (D13)

This material was prepared by the method of description 6. λmax (MeOH) 405, 382, 363 nm.

ʋmax (KBr) 3390, 1705 cm ^-1.

δ¹H (400 MHz) [(CD₃)₂SO: MeOH, 5:1]. Characteristic signals include:- 0.93 (3H, d, J 7.1Hz), 1.05 (3H, d, J 6.4 Hz), 1.13 (3H, d, J 6.4Hz), 1.18 (3H, d, J 5.9 Hz), 3.68 (1H, d, J 2.7Hz), 4.42 (1H, s), 5.43 (1H, dd, J 14.4, 10.0Hz), 5.96 (1H, dd, J l5.2, 8.9Hz).

Mass spectrum (FAB: Thiodiethanol-Na matrix). Found: MNa⁺ 1297. C₆₈H₉₅N₃O₂₀ requires M, 1273.65.

Example 1

Amphotericin B 16-(N-methoxy)carboxamide (E1)

To N-(9-fluorenylmethoxycarbonyl)amphotercin B 16-(N-methoxy)carboxamide (0.093g, 0.079 mmol) dissolved in dimethyl sulphoxide:methanol (4:1, 5mL) under nitrogen was added piperidine (0.050 mL, 0.043g, 0.50 mmol) and the mixture stirred for 1.5 hours. The solution was poured into diethyl ether (1L) and the precipitate filtered. The solid was washed with diethyl ether and dried in vacuo giving the title product (E1) (64mg). λmax (MeOH) 405 (ε 139277), 382 (ε 123950), 363 (ε 74541) nm. ʋmax (KBr) 3427 cm^-1. δ¹H (400 MHz) [CD₃OD: (CD₃)₂SO; 1:3]. Characteristic signals include;- 0.94 (3H, d, J6.91 Hz), 1.16 (3H, d, J6.15 Hz), 3.63 (3H, s), 4.36 (1H, s), 5.26 (1H, multiplet), 5.42 (1H, dd, J14.36 and 9.96 Hz), 5.98 (1H, dd, J15.36 and 8.85 Hz) and 6.07-6.50 (12H, complex) ppm. δ¹³C (68 MHz) [CD₃OD:(CD₃)₂SO; 1:3] 12.17, 17.06, 18.08, 18.65, 29.77, 35.45, 37.08, 40.13, 40.40, 42.27, 42.93, 44.88, 46.62, 54.30, 56.83, 63.38, 64.69, 65.41, 66.95, 67.43, 68.30, 69.39, 70.12, 70.45, 73.47, 73.81, 74.05, 74.5l, 75.37, 77.72, 97.47, 97.99, 129.11, 131.33-134.25 (m), 137.04, 137.16, 169.20, 171.08.

Mass spectrum (FAB: Thiodiethanol-Na matrix). Found: MNa⁺, 975.5. C₄₈H₇₆N₂O₁₇ requires m, 952.5. Example 2

Amphotericin B 16-( N-hydroxy)carboxamide (E2) To N-9-fluorenylmethoxycarbonyl)amphotericin B 16-(N-hydroxy)carboxamide (0.063g, 0.054mmol) dissolved in dry

dimethylsulphoxide:methanol (2:1, 0.75mL) was added piperidine

(0.013mL, 0.011g, 0.13mmol) and the mixture stirred under nitrogen for 2 hours. Methanol (0.16mL) was added, the solution poured into diethyl ether (200mL) and the precipitate filtered. The solid was washed with diethyl ether (100mL) and dried in vacuo giving the title product (E2) (0.04g). λmax (MeOH) 406 (ε 133310), 382 (ε 120770), 363 (ε 75870) nm. ʋmax (KBr) 3409, 3368, 1717, 1653cm^-1. δ¹H (400 MHz) [CD₃OD:(CD₃)₂SO; 1:3]. Characteristic signals include:- 0.94 (3H, d, J6.97 (Hz), 1.06 (3H, d, J6.27 Hz), 1.13 (3H, d, J6.14 Hz), 1.17 (3H, d, J6.01 Hz), 2.31 (1H, multiplet), 4.38 (2H, multiplet), 5.26 (1H, multiplet), 5.43 (1H, dd, J13.71 and 10.26 Hz), 5.99 (1H, dd, J15.13 and 8.66 Hz) and 6.11-6.50 (12H, complex) ppm. δ¹³C (68 MHz) [CD₃OD: (CD₃)₂SO; 1:3] 12.18, 17.07, 18.11, 18.66, 29.79, 35.46, 37.31, 39.92, 40.40, 42.30, 42.90, 44.72, 45.00, 46.74, 54.34, 56.50, 64.70, 65.58, 67.00, 68.30, 69.45, 70.18, 70.35, 73.42, 73.63, 74.10, 74.51, 75.59, 77.75, 97.51, 98.01, 129.12, 131.80-134.28 (m), 137.07, 137.34, 169.29, 171.11.

Mass spectrum (FAB: Thiodiethanol-Na matrix). Found: MNa⁺, 961.5. C₄₇H₇₄N₂O₁₇ requires m, 938.5.

Example 3

Amphotericin B 16-(N-n-prop-2-enyl-1-oxy) carboxamide (E3)

This example was prepared from the corresponding N-(9- fluorenylmethoxycarbonyl) amphotericin B derivative by the method described in example 1. λmax (MeOH) 405, 382, 363 nm. ʋmax (KBr) 3410, 1665 cm^-1. δ¹H (400 MHz) [CD₃OD:(CD₃)₂SO, 1:5]. Characteristic signals include 0.93 (3H, d, J 7.1Hz), 1.05 (3H, d, J 6.4Hz), 1.13 (3H, d, J 6.4Hz), 1.16 (3H, d, J 6.1Hz), 2.39 (1H, d, J 9.5, 3Hz), 2.94 (1H, t, J 9.2Hz), 3.65 (1H, d, J 3Hz), 5.43 (1H, dd, J 14,10Hz).

Mass spectrum (FAB: Thiodiethanol-Na matrix). Found: MNa⁺ 1002. C₅₀H₇₈N₂O₁₇ requires M, 978.5.

Example 4

Amphotericin B 16-(N-methoxy, N-methyl) carboxamide (E4)

This example was prepared from the corresponding N-(9-fluorenylmethoxycarbonyl) amphotericin B derivative by the method described in example 1. λmax (MeOH) 405, 382, 363 nm. ʋmax (KBr) 3410, 1710, 1635 cm^-1.

δ¹H (400 MHz) [CD₃OD: (CD₃)₂SO, 1:5]. Characteristic signals include 0.93 (3H, d, J 7.1Hz), 1.05 (3H, d, J 6.3Hz), 1.13 (3H, d, J 6.3Hz), 1.17 (3H, d, J 6.1Hz), 3.61 (1H, d, J 2.6Hz), 3.72 (3H, s), 5.25 (1H, dd, J 6.3, 2Hz), 5.43 (1H, dd, J 14.4, 10.1Hz), 5.97 (1H, dd, J 15.2, 9Hz).

Mass spectrum (FAB: Thiodiethanol-Na matrix). Found: MNa⁺ 989.

C₄₉H₇₈N₂O₁₇ requires M, 966.5.

Example 5

Amphotericin B 16-[N-(2-hydroxyethoxy)] carboxamide (E5)

This example was prepared from the corresponding N-(9- fluorenylmethoxycarbonyl) amphotericin B derivative by the method described in example 1. λmax (MeOH) 405, 382, 363 nm. ʋmax (KBr) 3400 cm^-1.

δ¹Η (400 MHz) [CD₃OD: (CD₃)₂SO, 1:5]. Characteristic signals include 0.93 (3H, d, J 7.1Hz), 1.05 (3H, d, J 6.4Hz), 1.13 (3H, d, J 6.4Hz), 1.16

(3H, d, J 6.0Hz), 2.46 (1H, dd, J 9.6, 2.7Hz), 3.66 (1H, d, J 2.7Hz), 3.83

(2H, t, J 4.7Hz), 4.35 (1H, s), 5.43 (1H, dd, J 14.4, 10.2Hz), 5.97 (1H, dd, J

15.2, 8.8Hz). λmax (MeOH) 405, 382, 363 nm. ʋmax (KBr) 3405 cm^-1.

Mass spectrum (FAB: Thiodiethanol-Na matrix). Found: MNa⁺ 1006.

C₄₉H₇₈N₂O₁₈ requires M, 983. Example 6

Amphotericin B 16-N-[2-(4-morpholino) ethoxy] carboxamide (E6)

This example was prepared from the corresponding N-(9-fluorenylmethoxycarbonyl) amphotericin B derivative by the method described in example 1. λmax (MeOH) 405, 382, 363 nm. ʋmax (KBr) 3400, 1665 cm^-1.

δ ¹H (400 MHz) [CD₃OD: (CD₃)₂SO, 1:5]. Characteristic signals include 0.94 (3H, d, J 7.1Hz), 1.05 (3H, d, J 6.4Hz), 1.13 (3H, d, J 6.4Hz), 1.16

(3H, d, J 6.1Hz), 2.36 (1H, dd, J 9.6, 3.0Hz), 3.63 (1H, d, J 3Hz), 5.42 (1H, dd, J 13.4, 10.2Hz), 5.98 (1H, dd, J 15.2, 8.8Hz).

Mass spectrum (FAB: Thiodiethanol-Na matrix). Found: MNa+ 1074.5. C₅₃H_85N3O₁₈ requires M, 1051.5.

Pharmacological Test Data

Method

The Minimum Inhibitory Concentration (MIC) was determined by diluting the test compound in a broth medium in a microtitre tray. The organisms, which had been grown previously in a broth medium, were diluted and added to the wells to provide a final inoculum of approximately 10⁵ colony-forming units per well. The trays were incubated at 37°C and the turbidity of each well noted at intervals. The MIC was taken as the lowest concentration (in μg/ml) which prevented significant growth.

Results Minimum Inhibitory Concentration (μg/ml)

(determined after 2 and 3 days incubation)

* Inoculum 10⁵ cells/ml

YNB: Yeast Nitrogen Base Broth

SAB: Sabouraud's Dextrose Broth.

Claims

1. A compound of formula (I) or a pharmaceutically acceptable salt thereof:

wherein R₁ is a group CO.N(R₅)OR₆ in which R₅ is hydrogen, C_1-6 alkyl, C_3-6 alkenyl, C_3-6 cycloalkyl, C_3-6 cycloalkyl -C_1-6 alkyl, aryl C_1-6 alkyl, heteroaryl C_1-6 alkyl, aryl, heteroaryl in which any aryl or heteroaryl moiety is optionally substituted, R₆ is hydrogen, C_1-6 alkyl, C_3-6 alkenyl, C_3-6 cycloalkyl, C_3-6 cycloalkyl -C_1-6 alkyl, aryl C_1-6 alkyl, heteroaryl C_1-6 alkyl, aryl, heteroaryl, in which any aryl or heteroaryl moiety is optionally substituted, C_2-6 hydroxyalkyl, a group (CH₂)_nNR₇R₈ in which n = 2 to 6, R₇ and R₈ independently represent hydrogen or C_1-6 alkyl or together with the nitrogen to which they are attached from a group of formula (i);

or R₆ is a group of formula (ii);

in which t is 1 to 6 and R₉ is hydrogen, C_1-6 alkyl or C_3-6 alkenyl;

or R₆ is a group of formula (iii);

R₂ is hydroxy or C_1-6 alkoxy;

R₃ is amino or a derivative thereof;

and R₄ is hydrogen or hydroxy; or R₂ and R₄ together represent a bond.

2. A compound according to claim 1 in which R₂ is hydroxy.

3. A compound according to claim 1 or 2 in which R₃ is amino.

4. A compound according to any one of claims 1 to 3 in which R₄ is hydrogen.

5. A compound according to any one of claims 1 to 4 in which R₅ in the variable R₁ is methyl or hydrogen.

6. A compound according to any one of claims 1 to 5 in which R₆ in the variable R₁ is hydrogen, methyl, prop-2-enyl, hydroxyethyl or N- ethylmorpholino.

7. A compound according to claim 1 which is selected from the list consisting of:

Amphotericin B 16-(N-methoxy)carboxamide, Amphotericin B 16-(N- hydroxy)carboxamide, Amphotericin B 16-(N-n-prop-2-enyl-1-oxy) carboxamide, Amphotericin B 16-(N-methoxy, N-methyl) carboxamide,

Amphotericin B 16-[N-(2-hydroxyethoxy)] carboxamide, Amphotericin B

16-N-[2-(4-morpholino) ethoxy] carboxamide or a pharmaceutically acceptable salt thereof.

8. A process for the preparation of compounds of formula (I) as defined in claim 1 which process comprises the reaction of a compound of formula (II):

wherein R₅ is as defined in relation to formula (I) as defined in claim 1 and R₆' is R₆ as defined in relation to formula (I) as defined in claim 1 or a group convertible thereto, and thereafter optionally or as necessary in any appropriate order, converting R₆' when other than R₆ to R₆, converting NHR₃' to R₃, removing the R₁₂ silyl protecting groups, interconverting R₂ and R₄, and forming a pharmaceutically acceptable salt.

9. A pharmaceutical composition comprising a compound of the formula (I) as defined in claim 1 or a pharmaceutically acceptable salt thereof together with a pharmaceutically acceptable diluent or carrier.

10. A compound of formula (I) as defined in claim 1 or a

pharmaceutically acceptable salt thereof for use as an active therapeutic substance.

11. A compound of formula (I) as defined in claim 1 or a

pharmaceutically acceptable salt thereof for use in the treatment of fungal infections.

12. A method of treatment of fungal infections in animals, which comprises administering an effective anti-fungal amount of a compound of formula (I) as defined in claim 1 or a pharmaceutically acceptable salt thereof to the animal.

13. The use of a compound of formula (I) as defined in claim 1 or a pharmaceutically acceptable salt thereof for the manufacture of a medicament for use in the treatment of fungal infections in animals.