Title of Invention

"A TAXOID OF FORMULA I AND PROCESS THEREOF"

Abstract

A taxoid of formula: in which: Z represents a hydrogen atom or a radical of formula: in which: R1 represents a benzoyl radical or a radical R2-OCO- in which R2 represents a tert-butyl radical and R3 represents an isobutyl, isobutenyl, butenyl, cyclohexyl, phenyl, 2-furyl, 3-furyl, 2-thienyl, 3-thienyl, 2-thiazolyl, 4-thiazolyl or 5-thiazolyl radical, and R4 and R5, which may be identical or different, each represent a methoxy, ethoxy or propoxy radical.

Full Text

The present invention relates to a taxoid of formula I and process thereof. The present invention relates to taxoids of formula: (Formula Removed) in which: Z represents a hydrogen atom or a radical of formula: (Formula Removed) in which: R1 represents a benzoyl radical optionally substituted by one or more identical or different atoms or radicals chosen from halogen, alkyl containing 1 to 4 carbon atoms, alkoxy containing 1 to 4 carbon atoms and trifluoromethyl, a thenoyl or furoyl radical or a radical R2-0-CO- in which R2 represents: - an alkyl radical containing 1 to 8 carbon atoms, an alkenyl radical containing 2 to 8 carbon atoms, an alkynyl radical containing 3 to 8 carbon atoms, a cycloalkyl radical containing 3 to 6 carbon atoms, a cycloalkenyl radical containing 4 to 6 carbon atoms or a bicycloalkyl radical containing 7 to 10 carbon atoms/ these radicals being optionally substituted by one or more substltuents chosen from halogen, hydroxyl, alkoxy containing 1 to 4 carbon atoms, dialkylamino in which •ach alkyl portion contains 1 to 4 carbon atoms, piperidino, morpholino, l-piperazinyl (optionally substituted at the 4-position by an alkyl radical containing 1 to 4 carbon atoms or with a phenylalkyl radical in which the alkyl portion contains 1 to 4 carbon atoms), cycloalkyl containing 3 to 6 carbon atoms, cycloalkenyl containing 4 to 6 carbon atoms, phenyl (optionally substituted by one or more identical or different substituents chosen from halogen, alkyl containing 1 to 4 carbon atoms and alkoxy containing l to 4 carbon atoms), cyano, carboxyl and alkoxycarbonyl in which the alkyl portion contains 1 to 4 carbon atoms, - a phenyl or a- or /J-naphthyl radical optionally substituted by one or more identical or different substituents chosen from halogen, alkyl containing l to 4 carbon atoms and alkoxy containing 1 to 4 carbon atoms, or a 5-membered aromatic heterocyclic radical, - or a saturated heterocyclic radical containing 4 to 6 carbon atoms, optionally substituted by one or more alkyl radicals containing 1 to 4 carbon atoms, R? represents an alkyl radical containing 1 to 8 carbon atoms, an alkenyl radical containing 2 to 8 carbon atoms, an alkynyl radical containing 2 to 8 carbon atoms, a cycloalkyl radical containing 3 to 6 carbon atoms, a phenyl or a- or /3-naphthyl radical optionally substituted by one or more identical or different substituents chosen from halogen, alkyl, alkenyl, alkynyl, aryl, aralkyl, alkoxy, alkylthio, aryloxy, arylthio, hydroxyl, hydroxyalkyl, mercapto, formyl, acyl, acylamino, aroylamino, alkoxycarbonylamino, amino, alkylamino, dialkylamino, carboxyl, alkoxycarbonyl, carbamoyl, alkylcarbamoyl, dialkylcarbamoyl, cyano, nitro and trifluoromethyl, or a 5-membered aromatic heterocycle containing one or more identical or different hetero atoms chosen from nitrogen, oxygen and sulphur atoms and optionally substituted by one or more identical or different substituents chosen from halogen, alkyl, aryl, amino, alkylamino, dialkylamino, alkoxycarbonylamino, acyl, arylcarbonyl, cyano, carboxyl, carbamoyl, alkylcarbamoyl, dialkylcarbamoyl and alkoxycarbonyl, on the understanding that, in the substituents of the phenyl, a- or 0-naphthyl and aromatic heterocyclic radicals, the alkyl radicals and the alkyl portions of other radicals contain 1 to 4 carbon atoms, and that the alkenyl and alkynyl radicals contain 2 to 8 carbon atoms, and that the aryl radicals are phenyl or a- or /3-naphthyl radicals, R4 represents an alkoxy radical containing 1 to 6 carbon atoms, an alkenyloxy radical containing 3 to 6 carbon atoms, an alkynyloxy radical containing 3 to 6 carbon atoms, a cycloalkyloxy radical containing 3 to 6 carbon atoms or a cycloalkenyloxy radical containing 4 to 6 carbon atoms, these radicals being optionally substituted by one or more halogen atoms or with an alkoxy radical containing 1 to 4 carbon atoms, an alkylthio radical containing l to 4 carbon atoms, a carboxyl radical, an alkyloxycarbonyl radical in which the alkyl portion contains l to 4 carbon atoms, a cyano radical or a carbamoyl radical or an N-alkylcarbamoyl or N,N-dialkylcarbamoyl radical in which each alkyl portion contains l to 4 carbon atoms or, with the nitrogen atom to which it is attached, forms a saturated 5- or 6-membered heterocyclic radical optionally containing a second hetero atom chosen from oxygen, sulphur or nitrogen atoms, optionally substituted by an alkyl radical containing l to 4 carbon atoms, a phenyl radical or a phenylalkyl radical in which the alkyl portion contains l to 4 carbon atoms, R; represents an alkoxy radical containing 1 to 6 carbon atoms, an alkenyloxy radical containing 3 to 6 carbon atoms, an alkynyloxy radical containing 3 to 6 carbon atoms, a cycloalkyloxy radical containing 3 to 6 carbon atoms or a cycloalkenyloxy radical containing 3 to 6 carbon atoms, these radicals being optionally substituted by one or more halogen atoms or with an alkoxy radical containing l to 4 carbon atoms, an alkylthio radical containing 2 to 4 carbon atoms, a carboxyl radical, an alkyloxycarbonyl radical in which the alkyl portion contains l to 4 carbon atoms, a cyano radical, a carbamoyl radical or an N-alkylcarbamoyl or N,N-dialkyIcarbamoyl radical in which each alkyl portion contains i to 4 carbon atoms or, with the nitrogen atom to which it is attached, forms a saturated 5- or 6-membered heterocyclic radical optionally containing a second hetero atom chosen from oxygen, sulphur or nitrogen atoms, optionally substituted by an alkyl radical containing 1 to 4 carbon atoms, a phenyl radical or a phenylalkyl radical in which the alkyl portion contains 1 to 4 carbon atoms. Unless otherwise stated all alkyl, alkenyl and alkynyl groups and moieties may be straight- or branched-chain. Preferably, the aryl radicals which R3 may represent are phenyl or a- or 0-naphthyl radicals optionally substituted by one or more substituents chosen from halogen atoms (e.g. fluorine, chlorine, bromine, iodine) and alkyl, alkenyl, alkynyl, aryl, arylalkyl, alkoxy, alkylthio, aryloxy, arylthio, hydroxyl, hydroxyalkyl, mercapto, formyl, acyl, acylamino, aroylamino, alkoxycarbonylamino, amino, alkylamino, dialkylamino, carboxyl, alkoxycarbonyl, carbamoyl, dialkylcarbamoyl, cyano, nitro and trifluoromethyl radicals, on the understanding that the alkyl radicals and the alkyl portions of the other radicals contain l to 4 carbon atoms, that the alkenyl and alkynyl radicals contain 2 to 8 carbon atoms and that the aryl radicals are phenyl or a- or /3-naphthyl radicals. Preferably, the heterocyclic radical which R3 may represent is a 5-membered aromatic heterocyclic radical containing one or more identical or different atoms chosen from nitrogen, oxygen and sulphur atoms, optionally substituted by one or more identical or different substituents chosen from halogen atoms (e.g. fluorine, chlorine, bromine, iodine) and alkyl radicals containing 1 to 4 carbon atoms, aryl radicals containing 6 to 10 carbon atoms, alkoxy radicals containing 1 to 4 carbon atoms, aryloxy radicals containing 6 to 10 carbon atoms, amino radicals, alkylamino radicals containing 1 to 4 carbon atoms, dialkylamino radicals in which each alkyl portion contains 1 to 4 carbon atoms, acylamino radicals in which the acyl portion contains 1 to 4 carbon atoms, alkoxycarbonylamino radicals containing l to 4 carbon atoms, acyl radicals containing l to 4 carbon atoms, arylcarbonyl radicals in which the aryl portion contains 6 to 10 carbon atoms, cyano, carboxyl or carbamoyl radicals, alkylcarbamoyl radicals in which the alkyl portion contains l to 4 carbon atoms, dialkylcarbamoyl radicals in which each alkyl portion contains 1 to 4 carbon atoms or alkoxycarbonyl radicals in which the alkoxy portion contains 1 to 4 carbon atoms. Preferably, the radicals R4 and R5, which may be identical or different, represent alkoxy radicals containing 1 to 6 carbon atoms, optionally substituted by a methoxy, ethoxy, ethylthio, carboxyl, methoxycarbonyl, ethoxycarbonyl, cyano, carbamoyl, N-methylcarbamoyl, N-ethy1carbamoyl, N,N-dimethylcarbamoyl, N,N-diethylcarbamoyl, N-pyrrolidinocarbonyl or N-piperidinocarbonyl radical. More especially, the present invention relates to the compounds of formula (I) in which Z represents a hydrogen atom or a radical of formula (II) in which R, represents a benzoyl radical or a radical R,-0-CO- in which R, represents a tert-butyl radical and R3 represents an alkyl radical containing 1 to 6 carbon atoms, an alkenyl radical containing 2 to 6 carbon atoms, a cycloalkyl radical containing 3 to 6 carbon atoms, a phenyl radical optionally substituted by one or more identical or different substituents chosen from halogen, alkyl, alkoxy, dialkylamino, acylamino, alkoxycarbonylamino and trifluoromethyl, or a 2- or 3-furyl, 2- or 3-thienyl or 2-, 4- or 5-thiazolyl radical, and R4 and R;, which may be identical or different, each represent an alkoxy radical containing 1 to 6 carbon atoms. Still more especially, the present invention relates to compounds of formula (I) in which 2 represents a hydrogen atom or a radical of formula (II) in which R, represents a benzoyl radical or a radical R2-O-CO- in which R2 represents a tert-butyl radical and R3 represents an isobutyl, isobutenyl, butenyl, cyclohexyl, phenyl, 2-furyl, 3-furyl, 2-thienyl, 3-thienyl, 2-thiazolyl, 4-thiazolyl or 5-thiazolyl radical, and R4 and R5, which may be identical or different, each represent a methoxy, ethoxy or propoxy radical. The compounds of formula (I) in which 2 represents a radical of formula (II) display noteworthy antitumour and antileukaemic properties. According to the present invention, the compounds of formula (I) in which 2 represents a radical of formula (II) may be obtained by esterification of a compound of formula: (Figure Removed) in which R4 and R? are as defined above, with an acid of formula: (Figure Removed) in which R, and R3 are as defined above, and either R6 represents a hydrogen atom and R7 represents a group protecting the hydroxyl function, or R6 and R7 together with the nitrogen atom to which they are attached form a saturated 5- or 6-membered heterocycle, or with a derivative of this acid, to obtain an ester of formula: (Figure Removed) in which R,, R3, R4, R?, R6 and R7 are as defined above, followed by replacement by hydrogen atom(s) of the protecting group R, or the heterocycle formed by R6 and R7. The esterification with an acid of formula (IV) may be performed in the presence of a condensing agent (e.g. carbodiimide, reactive carbonate) and an activating agent (e.g. aminopyridines) in an organic solvent (e.g. ethers, esters, ketones, nitriles, aliphatic hydrocarbons, halogenated aliphatic hydrocarbons, aromatic hydrocarbons) at a temperature of between -10 and 90°C. The esterification may also be carried out using the acid of formula (IV) in the form of a symmetrical anhydride, working in the presence of an activating agent (e.g. aminopyridines) in an organic solvent (e.g. ethers, esters, ketones, nitriles, aliphatic hydrocarbons, halogenated aliphatic hydrocarbons, aromatic hydrocarbons) at a temperature of between o and 90°C. The esterification may also be carried out using the acid of formula (IV) in halide form or in the form of a mixed anhydride, with an aliphatic or aromatic acid, optionally prepared in situ, in the presence of a base (e.g. tertiary aliphatic amine), working in an organic solvent (e.g. ethers, esters, ketones, nitriles, aliphatic hydrocarbons, halogenated aliphatic hydrocarbons, aromatic hydrocarbons) at a temperature of between 0 and 80°C. When R6 represents a hydrogen atom, R7 preferably represents a methoxymethyl, l-ethoxyethyl, benzyloxymethyl, trimethylsilyl, triethylsilyl, /J-trimethylsilylethoxymethyl, benzyloxycarbonyl or tetrahydropyranyl radical. When R6 and R7 together with the nitrogen atom to which they are attached form a 5- or 6-membered heterocycle, the latter is preferably an oxazolidine ring optionally monosubstituted or gem-disubstituted at the 2-position. Replacement by hydrogen atom(s) of the protecting group R7 or the heterocycle formed by R6 and R7 may be performed, depending on their nature, in the following manner: 1) when R6 represents a hydrogen atom and R7 represents a group protecting the hydroxyl function, replacement of the protective group by a hydrogen atom is performed using an inorganic acid (e.g. hydrochloric acid, sulphuric acid, hydrofluoric acid) or organic acid (e.g. acetic acid, methanesulphonic acid, trifluoromethanesulphonic acid, p-toluenesulphonic acid) used alone or mixed, working in an organic solvent chosen from alcohols, ethers, esters, aliphatic hydrocarbons, halogenated aliphatic hydrocarbons, aromatic hydrocarbons or nitriles at a temperature of between -10 and 60°C, or by means of a source of fluoride ions such as a hydrofluoric acid/triethylamine complex, or by catalytic hydrogenation, 2) when Rft and R7 together form a saturated 5- or 6- membered heterocycle, and more especially an oxazolidine ring of formula: (Figure Removed) in which R, is as defined above and Rx and R9, which may be identical or different, represent a hydrogen atom or an alkyl radical containing 1 to 4 carbon atoms, or an aralkyl radical in which the alkyl portion contains 1 to 4 carbon atoms and the aryl portion (preferably a phenyl radical) is optionally substituted by one or more alkoxy radicals containing l to 4 carbon atoms, or an aryl radical (preferably a phenyl radical) optionally substituted by one or more alkoxy radicals containing 1 to 4 carbon atoms, or alternatively Rg represents an alkoxy radical containing 1 to 4 carbon atoms or a trihalomethyl radical such as trichloromethyl or a phenyl radical substituted by a trihalomethyl radical such as trichloromethyl and Ry represents a hydrogen atom, or alternatively Rs and R9/ together with the carbon atom to which they are attached, form a 4- to 7-membered ring, replacement by hydrogen atoms of the heterocycle formed by R6 and R7 may be performed, depending on the meanings of R,, R^ and RM, in the following manner: a) when R, represents a tert-butoxycarbonyl radical and Rx and R9/ which may be identical or different, represent an alkyl radical or an aralkyl (e.g. benzyl) or aryl (e.g. phenyl) radical, or alternatively RB represents a trihalomethyl radical or a phenyl radical substituted by a trihalomethyl radical and R9 represents a hydrogen atom, or alternatively R8 and R9 together form a 4- to 7-membered ring, by treatment of the ester of formula (V) with an inorganic or organic acid, where appropriate in an organic solvent such as an alcohol, yields a compound of formula: (Figure Removed) in which R3, R4 and R5 are as defined above, which is acylated using benzoyl chloride in which the phenyl ring is optionally substituted or by using thenoyl chloride, furoyl chloride or a compound of formula: R2-0-CO-X (VIII) in which R: is as defined above and X represents a halogen atom (e.g. fluorine, chlorine) or a residue -O-R2 or -O-CO-O-R,, to obtain a compound of formula (I) in which Z represents a radical of formula (II). Preferably, the compound of formula (V) is treated with formic acid at a temperature of about 20°C to yield the compound of formula (VII). Preferably, the acylation of the compound of formula (VII) using a benzoyl chloride in which the phenyl radical is optionally substituted or by using thenoyl chloride, furoyl chloride or a compound of formula (VIII) is performed in an inert organic solvent chosen from esters such as ethyl acetate, isopropyl acetate or n-butyl acetate and halogenated aliphatic hydrocarbons such as dichloromethane or It2-dichloroethane, in the presence of an inorganic base such as sodium bicarbonate or an organic base such as triethylamine. The reaction is performed at a temperature of between 0 and 50°c, and preferably at a temperature of about 20°c. b) when R, represents an optionally substituted benzoyl radical, a thenoyl or furoyl radical or a radical R2O-CO- in which R2 is as defined above, R,, represents a hydrogen atom or an alkoxy radical containing 1 to 4 carbon atoms or a phenyl radical substituted by one or more alkoxy radicals containing 1 to 4 carbon atoms and Rv represents a hydrogen atom, replacement by hydrogen atoms of the heterocycle formed by R6 and R7 may be performed in the presence of an inorganic acid (e.g. hydrochloric acid, sulphuric acid) or organic acid (e.g. acetic acid, methanesulphonic acid, trifluoromethanesulphonic acid, p-toluenesulphonic acid) used alone or mixed in a stoichiometric or catalytic amount, working in an organic solvent chosen from alcohols, ethers, esters, aliphatic hydrocarbons, halogenated aliphatic hydrocarbons and aromatic hydrocarbons at a temperature of between -10 and 60°c, and preferably between 15 and 30°c. According to the invention, the compounds of formula (III), that is to say the compounds of formula (I) in which Z represents a hydrogen atom and R4 and R5 are as defined above, may be obtained from 10-deacetylbaccatin III of formula: (Figure Removed) Preferably, the hydroxyl functions at the 7-and 13-positions are selectively protected, for example in the form of a silyl diether which may be obtained by the action of a silyl halide of formula: (RJ^-Si-Hal (X) in which the symbols R, which may be identical or different, represent an alkyl radical containing 1 to 6 carbon atoms, optionally substituted by a phenyl radical, or a cycloalkyl radical containing 3 to 6 carbon atoms or a phenyl radical, on 10-deacetylbaccatin III, to obtain a compound of formula: (Figure Removed) in which R is as defined above, followed by the action of a compound of formula: R'4-X, (XII) in which R'4 represents a radical such that R'4-O is identical to R4 as defined above and X, represents a reactive ester residue such as a sulphuric or sulphonic ester residue or a halogen atom, to obtain a compound of formula: (Figure Removed) in which R and R4 are as defined above, the silyl protective groups of which are replaced by hydrogen atoms to obtain a compound of formula: (Figure Removed) in which R4 is as defined above, which is etherified selectively at the 7-position by the action of a compound of formula: R'?-X2 (XV) in which R'; represents a radical such that R'?-o is identical to R; as defined above and X: represents a halogen atom or a reactive ester residue such as a sulphuric or sulphonic ester residue, to give the compound of formula (III). Generally, the silyl derivative of formula (X) is reacted with 10-deacetylbaccatin III in pyridine or triethylamine, where appropriate in the presence of an organic solvent such as an aromatic hydrocarbon, for instance benzene, toluene or xylenes, at a temperature between o°c and the refluxing temperature of the reaction mixture. Generally, the compound of formula (XII) is reacted with the compound of formula (XI), after metalation of the hydroxyl function at the 10-position by using an alkali metal hydride such as sodium hydride, an alkali metal amide such as lithium amide or an alkali metal alkylide such as butyllithium, working in an organic solvent such as dimethylformamide or tetrahydrofuran at a temperature of between 0 and 50°C. Generally, replacement by hydrogen atoms of the silyl protective groups of the compound of formula (XIII) is performed using an acid such as hydrofluoric acid or trifluoroacetic acid in the presence of a base such as triethylamine or pyridine optionally substituted by one or more alkyl radicals containing 1 to 4 carbon atoms, the base optionally being combined with an inert organic solvent such as a nitrile, for instance acetonitrile, or a halogenated aliphatic hydrocarbon such as dichloromethane, at a temperature of between 0 and 80°C. Generally, the reaction of the compound of formula (XV) with the compound of formula (XIV) is performed under the conditions described above for the reaction of the compound of formula (XII) with the compound of formula (XI). According to the invention, the compounds of formula (I) in which Z represents a radical of formula (II), and R4 and R5 are as defined above may also be obtained from a compound of formula: (Figure Removed) in which R,, R?, R6 and R7 are as defined above, by silylation at the 7-position using a compound of formula (X), to obtain a compound of formula: (Figure Removed) in which R, R,, R3, Rfc and R7 are as defined above, which is functionalized at the 10-position using a compound of formula (XII) to give a compound of formula: (Figure Removed) in which R, R,, R3/ R4, R6 and R7 are as defined above, the silyl protective group of which is then replaced by a hydrogen atom to give a compound of formula: (Figure Removed) in which R,, R,, R4/ Rh and R- are as defined above, which, by the action of a compound of formula (XV), yields the compound of formula (V), the protective groups of which are replaced by hydrogen atoms to give a compound of formula (I) in which Z represents a radical of formula (II). The reactions used for silylation, functionalization and replacement of the protective groups by hydrogen atoms are performed under conditions similar to those described above. The compounds of formula (XVI) may be obtained under the conditions described in European Patent 0,336,841, WO 92/09589 and WO 94/07878, or from the compounds of formula: (Figure Removed) in which R, and R, are as defined above/ according to known methods for protecting the hydroxyl function of the side chain without affecting the remainder of the molecule. According to the invention, compounds of formula (I) in which Z represents a hydrogen atom or a radical of formula (II) may be obtained by the action of activated Raney nickel, in the presence of an aliphatic alcohol containing 1 to 3 carbon atoms or an ether such as tetrahydrofuran or dioxane, on a compound of formula: (Figure Removed) in which R4 is as defined above and R' and R", which may be identical or different, represent a hydrogen atom or an alkyl radical containing l to 6 carbon atoms, an alkenyl radical containing 2 to 6 carbon atoms, an alkynyl radical containing 2 to 6 carbon atoms, a cycloalkyl radical containing 3 to 6 carbon atoms or a cycloalkenyl radical containing 3 to 6 carbon atoms, optionally substituted, or alternatively R' and R", together with the carbon atom to which they are attached, form a cycloalkyl radical containing 3 to 6 carbon atoms or a cycloalkenyl radical containing 4 to 6 carbon atoms, and Z, represents a hydrogen atom or a radical of formula: (Figure Removed) in which R,, R3, R(, and R7 are as defined above, to obtain a compound of formula: (Figure Removed) followed, when Z, represents a radical of formula (XXII), that is to say when the compound of formula (XXIII) is identical to the compound of formula (V), by replacement of the protecting group R7 or the heterocycle formed by R6 and R7 by hydrogen atom(s) under the conditions described above. Generally, the action of activated Raney nickel in the presence of an aliphatic alcohol or an ether is performed at a temperature of between -10 and 60°c. According to the invention, the compound of formula (XXI) in which 2, and R4 are as defined above may be obtained by the action of a sulphoxide of formula: R' R J I TV. (XXIV) in which R' and R" are as defined above, on a compound of formula (XIX). Generally, the reaction of the sulphoxide of formula (XXIV), preferably dimethyl sulphoxide, with the compound of formula (XIX) is performed in the presence of a mixture of acetic acid and acetic anhydride or a derivative of acetic acid such as a haloacetic acid at a temperature of between 0° and 50°C, and preferably at a temperature of about 25°C. The compounds of formula (I) obtained by carrying out the processes according to the invention may be purified according to known methods such as crystallization or chromatography. The compounds of formula (I) in which 2 represents a radical of formula (II) display noteworthy biological properties. In vitro, measurement of the biological activity is performed on tubulin extracted from pig's brain by the method of M.L. Shelanski et al., Proc. Natl. Acad. Sci. USA, 70, 765-768 (1973). Study of the depolymerization of microtubules to tubulin is performed according to the method of G. Chauviere et al., C.R. Acad. Sci., 293, series II, 501-503 (1981). In this study, the compounds of formula (I) in which Z represents a radical of formula (II) were shown to be at least as active as taxol and Taxotere. In vivo, the compounds of formula (I) in which Z represents a radical of formula (II) were shown to be active in mice grafted with B16 melanoma at doses of between 1 and 10 mg/kg administered intraperitoneally, as well as on other liquid or solid tumours. The compounds have antitumour properties, and more especially activity against tumours which are resistant to Taxol® or to Taxotere^. Such tumours are, for example, colon tumours which have a high expression of the mdr 1 gene (multiple drug resistance gene). Multiple drug resistance is a customary term relating to the resistance of a tumour to different compounds having different structures and mechanisms of action. Taxoids are generally known to be strongly recognized by experimental tumours such as P388/DOX, a cell line selected for its resistance to doxorubicin (DOX) which expresses mdr 1. The examples which follow illustrate the present invention. EXAMPLE 1 126 mg of dicyclohexylcarbodiimide and then 14 mg of 4-(N,N-dimethylamino)pyridine are added successively at a temperature in the region of 20°C to a suspension containing 217.8 mg of 4a-acetoxy-2a-benzoyloxy-50,20-epoxy-l/:?, 13a-dihydroxy-7/3,100-dimethoxy-9-oxo-il-taxene, 200 mg of (2R,4S,5R)-3-tert-butoxycarbonyl-2-(4-methoxyphenyl)-4-phenyl-l,3-oxazolidine-5-carboxylic acid and 50 mg of powdered 4& molecular sieve in 2 crn^ of ethyl acetate. The suspension obtained is stirred at a temperature in the region of 20°c under an argon atmosphere for 16 hours, and then concentrated to dryness under reduced pressure (0.27 kPa) at a temperature in the region of 40°C. The residue obtained is purified by chromatography at atmospheric pressure on 50 g of silica (0.063-0.2 mm) contained in a column 2 cm in diameter (elution gradient: ethyl acetate/dichloromethane from 10:90 to 40:60 by volume), collecting lO-cm3 fractions. Fractions containing only the desired product are pooled and concentrated to dryness under reduced pressure (0.27 kPa) at 40°C for 2 hours. 271.8 mg of 4a-acetoxy-2a-benzoyloxy-5#, 20-epoxy-l#-hydroxy-7/;J, I0#-dimethoxy-9-oxo-ll-taxen-13a-yl (2R,4S,5R)-3-tert-butoxycarbonyl- 2-(4-methoxyphenyl)-4-phenyl-l,3-oxazolidine-5-carboxylate are thereby obtained in the form of a white solid, the characteristics of which are as follows: 'H NMR spectrum (400 MHz; CDC13 with a few drops of CD3OD-d4; chemical shifts S in ppm; coupling constants J in Hz): 1.02 (s, 9H: C(CH3)3); 1.10 (s, 3H: CH3) ; 1.17 (a, 3H: CH,) ; 1.63 (s, 3H: CH3) ; from 1.65 to 1.85 and 2.60 (2 mts, 1H each; CH: at position 6); 1.78 (unres. comp., 3H: CHJ ; 2.02 and 2.15 (2 dd, J = 14 and 9, 1H each: CH, at position 14); 2.14 (s, 3H: CH,) ; 3.22 and 3.35 (2 s, 3H each: OCHJ ; 3.64 (d, J = 7, 1H: H at position 3); 3.73 (mt, 1H: H at position 7); 3.76 (s, 3H: ArOCH?) ; 4.06 and 4.16 (2 d, J = 8.5, 1H each; CH2 at position 20); 4.53 (d, J = 5, 1H: H at position 2'); 4.67 (s, 1H: H at position 10); 4.85 (broad d, J = 10, 1H: H at position 5); 5.36 (mt, 1H: H at position 3'); 5.52 (d, J = 7, 1H: H at position 2); 6.07 (mt, 1H: H at position 13); 6.33 (unres. comp., 1H: H at position 5'); 6.88 (d, J = 8, 2H: aromatic H at the ortho position with respect to OCH3) ; from 7.25 to 7.40 (mt, 7H: aromatic H at position 3' and aromatic H at the meta position with respect to OCH,) ; 7.43 (t, J = 7.5, 2H: OCOC6H? H at the meta position); 7.58 (t, J = 7.5, 1H: OCOC6H5 H at the para position); 7.96 (d, J = 7.5, 2H: OCOC6H? H at the ortho position). A solution of 446.3 mg of 4a-acetoxy-2a-benzoyloxy-5/?,20-epoxy-l/3-hydroxy-7/j, io/3-dimethoxy-9-oxo-ll-taxen-l3a-yl (2R,4S,5R)-3-tert-butoxycarbonyl-2- (4-methoxyphenyl)-4-phenyl-l,3-oxazolidine-5-carboxylate in 11.6 cm3 of a 0.1N solution of hydrogen chloride in ethanol is kept stirring at a temperature in the region of 0°C for 16 hours under an argon atmosphere. The reaction mixture is then diluted with 40 cm3 of dichloromethane and 5 cm1 of distilled water. After settling has taken place, the aqueous phase is separated and extracted with 5 cm1 of dichloromethane. The organic phases are combined, dried over magnesium sulphate, filtered through sintered glass and then concentrated to dryness under reduced pressure (0.27 kPa) at a temperature in the region of 40°C. 424.2 mg of a pale yellow solid are obtained, which product is purified by preparative thin-layer chromatography [12 Merck preparative silica gel 60F:54 plates, thickness 1 mm, application in solution in a methanol/dichloromethane (5:95 by volume) mixture, eluting with a methanol/dichloromethane (5:95 by volume) mixture]. After elution of the zone corresponding to the main product with a methanol/ dichloromethane (15:85 by volume) mixture, filtration through sintered glass and evaporation of the solvents under reduced pressure (0.27 kPa) at a temperature in the region of 40°C/ 126 mg of 4a-acetoxy-2a-benzoyloxy-5/3,20-epoxy-l/3-hydroxy-7/3, lO/3-dimethoxy-9-oxo-ll-taxen-13a-yl (2R,3S)-3-tert-butoxycarbonylamino-2-hydroxy-3-phenylpropionate are obtained in the form of an ivory-coloured foam, the characteristics of which are as follows: - optical rotation [a]1^ = -32.9 (c = 0.5; roethanol) - 'H NMR spectrum (400 MHz; CDC13; chemical shifts 6 in ppm; coupling constants J in Hz): 1.23 (s, 3H: CH?) ; 1.25 (s, 3H: CH-,) ; 1.39 (s, 9H: C(CH,)0; 1.70 (s, 1H: OH at position 1); 1.75 (s, 3H: CH3) ; 1.82 and 2.72 (2 mts, 1H each: CH, at position 6); 1.91 (s, 3H: CH3) ; 2.31 (limiting AB, 2H: CH: at position 14); 2.39 (s, 3H: COCHJ ; 3.33 and 3.48 (2 s, 3H each: OCH,) ; 3.48 (mt, 1H: OH at position 2'); 3.85 (d, J = 7, 1H: H 3); 3.88 (dd, J = 11 and 7, 1H: H 7); 4.20 and 4.33 (2 d, J = 8.5, 1H each: CH, at position 20); 4.65 (mt, 1H: H at position 2'); 4.83 (s, 1H: H at position 10); 5.00 (broad d, J = 10, 1H: H at position 5); 5.30 (broad d, J = 10, 1H: H at position 3'); 5.47 (d, J = 10, 1H: CONH); 5.66 (d, J = 7, 1H: H at position 2); 6.24 (broad t, J = 9, 1H: H at position 13); from 7.30 to 7.50 (mt, 5H: aromatic H at position 3'); 7-52 (t, J = 7.5, 2H: OCOCftH? H at the meta position); 7.63 (t, J = 7.5, 1H: OCOC6H? H at the para position); 8.12 (d, J = 7.5, 2H: OCOC6H? H at the ortho position). 4a-Acetoxy-2a-benzoyloxy-5/J, 20-epoxy-l/J, I3a-dihydroxy-7/2, lO/3-dimethoxy-9-oxo-il-taxene (or 7/3,10/3-dimethoxy-10-deacetoxybaccatin III) may be prepared in the following manner: 86 mg of sodium hydride at a concentration of 50 % by weight in liquid paraffin are added portionwise to a solution, maintained under an argon atmosphere, at a temperature in the region of o°c/ of 500 mg of 4a-acetoxy-2a-benzoyloxy-5/3,20-epoxy-i/3,7/3,I3a-trihydroxy-lo/3-methoxy-9-oxo-n-taxene in 5 cm3 of iodomethane and 0.5 cm3 of dimethylformamide. After 45 minutes at a temperature in the region of 0°C, the reaction mixture is diluted with 50 cm3 of ethyl acetate and 8 cm3 of distilled water. After settling has taken place/ the organic phase is separated and washed with twice 8 cm' of distilled water and then 8 cm3 of saturated aqueous sodium chloride solution, dried over magnesium sulphate, filtered through sintered glass and concentrated to dryness under reduced pressure (0.27 kPa) at a temperature in the region of 40°C. 570 mg of a pale yellow solid are thereby obtained, which product is purified by chromatography at atmospheric pressure on 50 g of silica (0.063-0.2 mm) contained in a column 2.5 cm in diameter, eluting with a methanol/dichloromethane (2:98 by volume) mixture and collecting 10-cm3 fractions. Fractions containing only the desired product are pooled and concentrated to dryness under reduced pressure (0.27 kPa) at 40°C for 2 hours. 380 mg of 4a-acetoxy-2a-benzoyloxy-5/3,20-epoxy-1/3, l3a-dihydroxy-7/J, lO/3-dimethoxy-9-oxo-ll-taxene are thereby obtained in the form of a pale yellow solid, the characteristics of which are as follows: - 'H NMR spectrum (400 MHz; CDC1?; with a few drops of CD3OD-d4; chemical shifts S in ppm; coupling constants J in Hz): 1.03 (s, 3H: CHA) ; 1.11 (s, 3H: CH-,) ; 1.65 (s, 3H: CH3) ; 1.72 and 2.67 (2 mts, 1H each: CH, at position 6); 2.05 (s, 3H: CH3) : 2.21 (limiting AB, J = 14 and 9, 2H: CH2 at position 14); 2.25 (s, 3H: COCH,) ; 3.26 and 3.40 (2 S, 3H each: OCH3) ; 3.85 (d, J = 7, 1H: H at position 3); 3.89 (dd, J = 11 and 6.5, 1H: H at position 7); 4.12 and 4.25 (2 d, J = 8.5, 1H each: CH2 at position 20); 4.78 (broad t, J = 9, 1H: H at position 13); 4.83 (s, 1H: H at position 10); 4.98 (broad d, J = 10, 1H: H at position 5); 5.53 (d, J = 1, 1H: H at position 2); 7.43 (t, J = 7.5, 2H: OCOC6H; H at the meta position); 7.56 (t, J = 7.5, 1H: OCOCf,H, H at the para position); 8.05 (d, J = 7.5, 2H: OCOC,,H; H at the ortho position). 4a-Acetoxy-2a-benzoyloxy-5/3,2 0-epoxy-1/3, 7/3, l3a-trihydroxy-lo$-methoxy-9-oxo-ll-taxene (or 10/3-methoxy-lO-deacetoxybaccatin III) may be prepared in the following manner: 50 cm1 of hydrogen fluoride/triethylamine complex (3HF.EtAN) are added slowly to a solution, maintained under an argon atmosphere, at a temperature in the region of 0°C, of 3.62 g of 4a-acetoxy-2a-benzoyloxy-5/3,20-epoxy~l/3-hydroxy-lO/3-methoxy-9-oxo-7/3,13a-bis (triethylsilyoxy)-ll-taxene in 30 cm3 of dichloromethane. After 48 hours at a temperature in the region of 20°C, the reaction mixture is poured into a suspension of 100 cm3 of supersaturated aqueous sodium hydrogen carbonate solution maintained at a temperature in the region of 0°C. After settling has taken place, the aqueous phase is separated and re-extracted with three times 80 cnr* of dichloromethane and then twice 80 cm3 of ethyl acetate. The organic phases are combined, dried over magnesium sulphate, filtered through magnesium sulphate and concentrated to dryness under reduced pressure (0.27 KPa) at a temperature in the region of 40°C. 3.45 g of a yellow foam are thereby obtained, which product is purified by chromatography at atmospheric pressure on 150 g of silica (0.063-0.2 mm) contained in a column 3.5 cm in diameter, eluting with a methanol/dichloromethane (5:95 by volume) mixture and collecting 35-cm3 fractions. Fractions containing only the desired product are pooled and concentrated to dryness under reduced pressure (0.27 kPa) at 40°C for 2 hours. 1.97 g of 4a-acetoxy-2a-benzoyloxy-5/J, 20-epoxy-l^, 7(3,13a-trihydroxy-10j3-methoxy-9-oxo-ll-taxene are thereby obtained in the form of a white solid, the characteristics of which are as follows: - 'H NMR spectrum (400 MHz; CDC1?; chemical shifts 6 in ppm; coupling constants J in Hz): 1.10 (s, 3H: CH3) ; 1.19 (s, 3H: CHj) ; 1.48 (d, J = 8.5, 1H: OH at position 13); 1.70 (s, 3H: CH?) ; 1.81 and 2.61 (2 mts, 1H each: CH2 at position 6); 2.09 (d, J = 5, 1H: OH at position 7); 2.11 (s, 3H: CH?) ; 2.30 (s, 3H: COCH?) ; 2.32 (d, J = 9, 2H: CH: at position 14); 3.48 (s, 3H: OCHJ ; 3.97 (d, J = 7, 1H: H at position 3); 4.18 and 4.33 (2 d, J = 8.5, 1H each: CH, at position 20); 4.31 (mt, 1H: H at position 7); 4.93 (rat, 1H: H at position 13); 4.99 (s, 1H: H at position 10); 5.01 (broad d, J = 10, 1H: H at position 5); 5.66 (d, J = 7, 1H: H at position 2); 7.49 (t, J = 7.5, 2H: OCOC6H5 H at the meta position); 7.63 (t, J = 7.5, 1H: OCOCtH5 H at the para position); 8.12 (d, J = 7.5, 2H: OCOC6H; H at the ortho position). 4a-Acetoxy-2a-benzoyloxy-50,20-epoxy-l|3-hydroxy-io£-methoxy-9-oxo-7^, I3a-bis (triethylsilyloxy)-11-taxene (or iO/3-methoxy-lO-deacetoxy-7,13-bis(triethylsilyl)baccatin III) may be prepared in the following manner: 375 mg of sodium hydride at a concentration of 50 % by weight in liquid paraffin are added portionwise to a solution, maintained under an argon atmosphere, at a temperature in the region of 0°C, of 5 g of 4a-acetoxy-2a-benzoyloxy-5/3, 20-epoxy-l/S, 10/3-dihydroxy-9-oxo-7/J, 13 a-bis (triethylsilyloxy) -11-taxene in 25 cm' of iodomethane. The solution is kept stirring for 45 minutes at a temperature in the region of 0°Cf and then for 5 hours 30 minutes at a temperature in the region of 20°c. The reaction mixture is cooled again to a temperature in the region of 0°C, and 125 mg of sodium hydride at a concentration of 50 % by weight in liquid paraffin are added portionwise. After 1 hour at 20°C and then 18 hours at 5°C, the reaction mixture is diluted by adding 50 cm? of dichloromethane and poured into 50 cm1 of saturated aqueous ammonium chloride solution, and settling is allowed to take place. The aqueous phase is separated and extracted with twice 30 cm3 of dichloroemethane, and the organic phases are then combined, washed with 10 cm3 of distilled water/ dried over magnesium sulphate, filtered through sintered glass and concentrated to dryness under reduced pressure (0.27 kPa) at a temperature in the region of 40°C. 5.15 g of a yellow foam are thereby obtained/ which product is purified by chromatography at atmospheric pressure on 300 g of silica (0.063-0.2 mm) contained in a column 5 cm in diameter (elution gradient: ethyl acetate/dichloromethane from 0:100 to 10:90 by volume), collecting 30-cm1 fractions. Fractions containing only the desired product are pooled and concentrated to dryness under reduced pressure (0.27 KPa) at 40°C for 2 hours. 3.62 g of 4a-acetoxy-2a-benzoyloxy-5/3,20-epoxy-l/3-hydroxy-lO/3-methoxy-9-oxo-7/J, I3a-bis (triethylsilyloxy) -ll-taxene are thereby obtained in the form of a pale yellow foam, the characteristics of which are as follows: - 'H NMR spectrum (600 MHz; CDC13; chemical shifts 6 in ppm; coupling constants J in Hz): 0.58 and 0.69 (2 mts, 6H each: ethyl CH;) ; 0.97 and 1.04 (2 t, J = 7.5, 9H each: ethyl CH,) ; 1.15 (s, 3H: CH,) ; 1.18 (s, 3H: CH?) ; 1.58 (s, 1H: OH at position 1); 1.68 (s, 3H: CH?); 1.89 and 2.48 (2 mts, 1H each: CH: at position 6); 2.04 (s, 3H: CH3) ; 2.15 and 2.23 (2 dd, J = 16 and 9, 1H each: CH, at position 14); 2.29 (s, 3H: COCH3) ; 3.40 (s, 3H: OCH,) ; 3.83 (d, J = 7, 1H: H: H at position 13); 4.15 and 4.30 (2 d, J = 8.5, 1H each: CH, at position 20); 4.43 (dd, J = 11 and 7, 1H: H at position 7); 4.91 (s, 1H: H at position 10); 4.96 (broad d, J = 10, 1H at position 5); 5.01 (broad t, J = 9, 1H: H at position 13); 5.62 (d, J = 7, 1H: H at position 2); 7.46 (t, J = 7.5, 2H: OCOC6H5 H at the meta position); 7.60 (t, J = 7.5, 1H: OCOC6H? H at the para position); 8.09 (d, J = 7.5, 2H: OCOC6H; H at the ortho position). 4a-Acetoxy-2ct-benzoyloxy-5£(, 20-epoxy-l/3,10/3-dihydroxy-9-oxo-7/3,13a-bis (triethylsilyloxy) -ll-taxene (or lO-deacetyl-7,13-bis(triethylsilyl)baccatin III) may be prepared in the following manner: 10.8 cm3 of triethylsilyl chloride are added to a solution, maintained under an argon atmosphere, at a temperature in the region of 20°c, of 14 g of 4a-acetoxy-2a-benzoyloxy-5/3, 20-epoxy-l/3, 7/3,10/3,13a-tetrahydroxy-9-oxo-ll-taxene (10-deacetylbaccatin III) in 50 cm3 of anhydrous pyridine. After 17 hours at a temperature in the region of 20°C, the reaction mixture is brought to a temperature in the region of 115°C and 10.8 cm3 of triethylsilyl chloride are then added. After 3 hours 15 minutes at a temperature in the region of 115°C, the reaction mixture is brought back to a temperature in the region of 20°C and diluted with 30 cm3 of ethyl acetate and 100 cm3 of distilled water. After settling has taken place, the aqueous phase is separated and extracted with twice 50 cm3 of ethyl acetate. The organic phases are combined, washed with 50 cm? of saturated aqueous sodium chloride solution/ dried over magnesium sulphate, filtered through sintered glass and then concentrated to dryness under reduced pressure (0.27 kPa) at a temperature in the region of 40°C. 63.1 g of a brown oil are thereby obtained, which product is purified by chromatography at atmospheric pressure on 800 g of silica (0.063-0.2 mm) contained in a column 7 cm in diameter (elution gradient: ethyl acetate/dichloromethane from 0:100 to 5:95 by volume), collecting 60-cm? fractions. Fractions containing only the desired product are pooled and concentrated to dryness under reduced pressure (0.27 kPa) at 40°C for 2 hours. 9.77 g of 4a-acetoxy-2a-benzoyloxy-5#, 20-epoxy-l^, 10/J-dihydroxy-9-0x0-7/3,13a-bis (triethylsilyloxy) -n-taxene are thereby obtained in the form of a cream-coloured foam, the characteristics of which are as follows: - 'H NMR spectrum (400 MHz; CDC1,; chemical shifts & in ppm; coupling constants J in Hz): 0.55 and 0.68 (2 mts, 6H each: ethyl CH,) ; 0.94 and 1.03 (2 t, J = 7.5, 9H each: ethyl CH,) ; 1.08 (s, 3H: CH3) ; 1.17 (s, 3H: CH3) ; 1.58 (s, 1H: OH at position 1); 1.73 (s, 3H: CH3) ; 1.91 and 2.57 (2 mts, 1H each: CH: at position 2); 2.04 (s, 3H: CH,) ; 2.12 and 2.23 (2 dd, J = 16 and 9, 1H each: CH2 at position 14); 2.30 (s, 3H: COCHJ ; 3.88 (d, J = 7, 1H: H at position 3); 4.16 and 4.32 (2 d, J = 8.5, 1H each: CH2 at position 20); 4.27 (d, J = 1, 1H: OH at position 10); 4.40 (dd, J = 11 and 7, 1H: H at position 7); 4.95 (broad d, J = 10, 1H: H at position 5); 4.95 (mt, 1H: H at position 13); 5.16 (d, J = i, 1H: H at position 10); 5.60 (d, J = 7, 1H: H at position 2); 7.46 (t, J = 7.5, 2H: OCOC6H5 H at the meta position); 7.60 (t, J = 7.5, 1H: OCOC6H5 H at the para position); 8.09 (d, J = 7.5, 2H: OCOC6H5 H at the ortho position). EXAMPLE 2 340 mg of 4a-acetoxy-2a-benzoyloxy-5/3,20-epoxy-l/3-hydroxy-7/3, lO/3-dimethoxy-9-oxo-n-taxen-l3a-yl (2R,48,5R)-3-tert-butoxycarbonyl-2-(4-methoxyphenyl)-4-phenyl-1,3-oxazolidine-5-carboxylate are dissolved in 8 cm3 of a 0.IN ethanolic solution of hydrochloric acid containing l % of water. The solution thereby obtained is stirred for 13 hours at a temperature in the region of 20°C and then for 80 hours at 4°C, and 20 cm? of dichloromethane are added. The organic phase is separated after settling has taken place and washed successively with 3 times 5 cm? of saturated aqueous sodium hydrogen carbonate solution, dried over magnesium sulphate, filtered and concentrated to dryness under reduced pressure (2.7 kPa) at 40°C. 300 mg of a white foam are obtained, which product is purified by chromatography on silica gel deposited on plates [gel 1 mm thick, plates 20 x 20 cm, eluent: dichloromethane/methanol (95:5 by volume)] in 80-mg fractions (4 plates). After localization with UV rays of the zone corresponding to the adsorbed desired product, this zone is scraped off and the silica collected is washed on sintered glass with 10 times 5 cm3 of ethyl acetate. The filtrates are combined and concentrated to dryness under reduced pressure (2.7 kPa) at 40°C. A white foam is obtained, which is repurified according to the same technique [3 plates: 20 x 20 x l mm; eluent: dichloromethane/ethyl acetate (90:10 by volume)]. 205 mg of 4a-acetoxy-2a-benzoyloxy-5/3/20-epoxy-l/3-hydroxy-7/J, lo/J-dimethoxy-9-oxo-ll-taxen-13a-yl (2R,3S)-3-tert-butoxycarbonylamino-2-hydroxy-3-phenylpropionate are thereby obtained in the form of a white foam, the characteristics of which are as follows: - optical rotation: [a]1,',, = -33 (c = 0.5; methanol) . - *H NMR spectrum (400 MHz; CDC17; chemical shifts 6 in ppm; coupling constants J in Hz): 1.23 (s, 3H: -CH?) ; 1.25 (s, 3H: -CH3) ; 1.39 [s, 9H: -C(CH:J,]; 1.70 ,(s, 1H: -OH at position 1); 1.75 (s, 3H: -CH,) ; 1.82 and 2.72 (2 mts, 1H each: -CH: at position 6); 1.91 (s, 3H: -CH3) ; 2.31 (limiting AB, 2H: -CH, at position 14); 2.39 (s, 3H: -COCH3) ; 3.33 and 3.48 (2 s, 3H each: -OCH3) ; 3.48 (mt, 1H: OH at position 2'); 3.85 (d, J = 7, 1H: -H at position 3); 3.88 (dd, J = 11 and 7, 1H: -H at position 7); 4.20 and 4.33 (2d, J = 8.5, 1H each: -CH, at position 20); 4.65 (mt, 1H: -H at position 2'); 4.83 (s, 1H: -H at position 10); 5.00 (broad d, J = 10, 1H: -H at position 5); 5.30 (broad d, J = 10, 1H: -H at position 3'); 5.47 (d, J = 10, 1H: -CONH-); 5.66 (d, J = 7, 1H: -H at position 2); 6.24 (broad t, J = 9, 1H: -H at position 13); from 7.30 to 7.50 (mt, 5H: -C6H, at position 3'); 7.52 [t, J = 7.5, 2H: -ococ6H:; (-H at position 3 and H at position 5)]; 7.63 [t, J = 7.5, 1H: -OCOC6H5 (-H at position 4)]; 8.12 [d, J = 7.5, 2H: -OCOCfcH5 (-H at position 2 and H at position 6)]. 4o-Acetoxy-2a-benzoyloxy-5/3,2 0-epoxy-l/2-hydroxy-7/3, 10/3-dimethoxy-9-oxo-ll-taxen-13a-yl (2R,4S,5R)-3-tert-butoxycarbonyl-2-(4-methoxyphenyl)-4-phenyl-l,3-oxazolidine-5-carboxylate may be prepared in the following manner: 100 cm? of an ethanolic suspension of activated nickel according to Raney (obtained from 80 cnr of the approximately 50 % commercial aqueous suspension by successive washing, to a pH in the region of 7, with 15 times 100 cnr1 of distilled water and with 5 times 100 cm' of ethanol) are added at a temperature in the region of 20°C to a solution, maintained under an argon atmosphere and kept stirring, of i g of 4a-acetoxy-2a-benzoyloxy-5/3,20-epoxy-l/3-hydroxy-7/3,10/3-bis(methylthiomethoxy)-9-oxo-ll-taxen-l3a-yl (2R,4S,5R)-3-tert-butoxycarbonyl-2-(4-methoxyphenyl)-4-phenyl-1,3-oxazolidine-5-carboxylate in 100 cm3 of anhydrous ethanol. The reaction medium is kept stirring for 24 hours at a temperature in the region of 20°C and then filtered through sintered glass. The sintered glass is washed with 4 times 80 cm? of ethanol, and the filtrates are combined and concentrated to dryness under reduced pressure (2.7 kPa) at 40°C. 710 mg of a yellow foam are obtained, which product is purified by chromatography on 60 g of silica (0.063-0.2 nun) contained in a column 2.5 cm in diameter [eluent: dichloromethane/ethyl acetate (90:10 by volume)], collecting 6-cm3 fractions. Fractions containing only the desired product are pooled and concentrated to dryness under reduced pressure (2.7 kPa) at 40°C. 350 mg of 4a-acetoxy-2a-benzoyloxy-5/J,20-epoxy-l/J-hydroxy-7/j, l00-dimethoxy-9-oxo-ll-taxen-13a-yl (2R,4S,5R)-3-tert-butoxycarbonyl-2-(4-methoxyphenyl)-4-phenyl-l,3-oxazolidine-5-carboxylate are thereby obtained in the form of a white foam. 4a-Acetoxy-2a-benzoyloxy-5/J,20-epoxy-l/3-hydroxy-7/3,10/J-bis (methylthiomethoxy) -9-oxo-ll-taxen-13ct-yl (2R, 4S, 5R) -3-tert-butoxycarbonyl-2- (4-methoxyphenyl)-4-phenyl-l, 3-oxazolidine-5-carboxylate may be prepared in the following manner: 2.3 cm3 of acetic acid and 7.55 cm3 of acetic anhydride are added at a temperature in the region of 20°C to a solution, maintained under an argon atmosphere and kept stirring, of 3.1 g of 4a-acetoxy-2a-benzoyloxy-5/3,20-epoxy-l/J-7/3, lO|3-trihydroxy-9-oxo-Il-taxen-l3a-yl (2R,4S,5R)-3-tert-butoxycarbonyl-2-(4-methoxyphenyl)-4-phenyl-l,3-oxazolidine-5-carboxylate dissolved in 102 cm3 of dimethyl sulphoxide. The reaction mixture is kept stirring for 7 days at a temperature in the region of 20°C, and then poured into a mixture of 500 cm3 of distilled water and 250 cm3 of dichloromethane. 30 cm3 of saturated aqueous potassium carbonate solution are then added with efficient stirring to a pH in the region of 7. After 10 minutes of stirring, the organic phase is separated after settling has taken place and the aqueous phase is re-extracted with twice 250 cm3 of dichloromethane. The organic phases are combined, washed with 250 cm3 of distilled water/ dried over magnesium sulphate, filtered and concentrated to dryness under reduced pressure (2.7 kPa) at 40°C. 5.2 g of a pale yellow oil are obtained, which product is purified by chromatography on 200 g of silica (0.063-0.4 mm) contained in a column 3 cm in diameter [eluent: dichloromethane/methanol (99:1 by volume)], collecting SO-cnr* fractions. Fractions containing only the desired product are pooled and concentrated to dryness under reduced pressure (2.7 kPa) at 40°C. 1.25 g of 4a-acetoxy-2a-benzoyloxy-5/3,20-epoxy-l/3-hydroxy-7/3,10/3-bis(methylthiomethoxy)-9-oxo-ll-taxen-13a-yl (2R,48,5R)-3-tert-butoxycarbonyl-2-(4-methoxyphenyl)-4-phenyl-l,3-oxazolidine-5-carboxylate are thereby obtained in the form of a white foam. 4a-Acetoxy-2a-benzoyloxy-5/3, 20-epoxy- 1/3,7/3, io/3-trihydroxy-9-oxo-ll-taxen-l3a-yl (2R, 4S, 5R) -3-tert-butoxycarbonyl-2-(4-methoxyphenyl)-4-phenyl-l,3-oxazolidine-5-carboxylate may be prepared in the following manner: A solution of 5.1 g of 4a-acetoxy-2a- benzoyloxy-50,20-epoxy-l/5-hydroxy-9-oxo-7/5,10/5-bis(2,2,2-trichloroethoxycarbonyloxy)-ll-taxen-13a-yl (2R,4S,5R)-3-tert-butoxycarbonyl-2-(4-methoxyphenyl)-4-phenyl-l,3-oxazolidine-5-carboxylate in a mixture of 100 cm3 of methanol and 100 cm? of acetic acid is heated, with stirring and under an argon atmosphere, to a temperature in the region of 60°C, and 10 g of powdered zinc are then added. The reaction mixture is then stirred for 15 minutes at 60°C, thereafter cooled to a temperature in the region of 20°C and filtered through sintered glass lined with celite. The sintered glass is washed with twice 15 cnv* of methanol. The filtrate is concentrated to dryness under reduced pressure (2.7 kPa) at a temperature in the region of 40°C. 50 cm' of ethyl acetate and 25 cm? of saturated aqueous sodium hydrogen carbonate solution are added to the residue. The organic phase is separated after settling has taken place and washed successively with 25 cm3 of saturated aqueous sodium hydrogen carbonate solution and with 25 cm7 of distilled water, then dried over magnesium sulphate, filtered through sintered glass and concentrated to dryness under reduced pressure (2.7 kPa) at 40°C. 3.1 g of 4a-acetoxy-2a-benzoyloxy-5/3,20-epoxy-l/5, 7/5, lO/5-trihydroxy-9-oxo-ll-taxen-13a-yl (2R,4S,5R)-3-tert-butoxycarbonyl-2-(4-methoxyphenyl)-4-phenyl-l,3-oxazolidine-5-carboxylate are thereby obtained in the form of a white foam. 4a-Acetoxy-2a-benzoyloxy-5/5, 20-epoxy-l/5- hydroxy-9-oxo-7/3,10/3-bis (2,2 , 2-trichloroethoxy-carbonyloxy)-n-taxen-l3a-yl (2R,4S,5R)-3-tert-butoxy-carbonyl-2-(4-methoxyphenyl)-4-phenyl-l,3-oxazolidine-5-carboxylate may be prepared under the conditions described in Patent WO 94/07878. EXAMPLE 3 76 rag of dicyclohexylcarbodiimide and then 8.5 mg of 4-(N,N-dimethylamino)pyridine are added successively at a temperature in the region of 20°C to a suspension containing 135 mg of 4a-acetoxy-2a-benzoyloxy-50, 20-epoxy-100-ethoxy-l/3, l3a-dihydroxy-7/3-methoxy-9-oxo-ll-taxene, 120 mg of (2R,4S,5R)-3-tert-butoxycarbonyl-2-(4-methoxyphenyl)-4-phenyl-l,3-oxazolidine-5-carboxylic acid and 50 mg of powdered 4& molecular sieve in l cm3 of anhydrous toluene. The suspension obtained is stirred at a temperature in the region of 20°C under an argon atmosphere for 1 hour, and then purified by direct application to a column for chromatography at atmospheric pressure on 30 g of silica (0.063-0.2 mm) contained in a column 2.5 cm in diameter (elution gradient: ethyl acetate/ dichloromethane from 2:98 to 10:90 by volume), collecting 10-cm3 fractions. Fractions containing only the desired product are pooled and concentrated to dryness under reduced pressure (2.7 kPa) at 40°C for 2 hours. 320.6 mg of a white solid are thereby obtained, which product is purified by preparative thin-layer chromatography: 10 Merck preparative silica gel 60F254 plates, thickness 0.5 mm, application in solution in dichloromethane, eluting with a methanol/ dichloromethane (3:97 by volume) mixture. After elution of the zones corresponding to the main products with a methanol/dichloromethane (15:85 by volume) mixture, filtration through cotton wool and then evaporation of the solvents under reduced pressure (2.7 kPa) at a temperature in the region of 40°C, 47.7 mg of 4a-acetoxy-2a-benzoyloxy-5/3, 20-epoxy-lO/3-ethoxy-l/3,I3a-dihydroxy-7/3-methoxy-9-oxo-ii-taxene are obtained in the form of a cream-coloured solid and 37 mg of 4a-acetoxy-2a-benzoyloxy-5/3, 20-epoxy-lO/3-ethoxy-l/3-hydroxy-7£-methoxy-9-oxo-li-taxen-i3a-yl (2R,4S,5R)-3-tert-butoxycarbonyl-2-(4-methoxyphenyl)-4-phenyl-l,3-oxazolidine-5-carboxylate are obtained in the form of a white foam, the characteristics of which are as follows: - 'H NMR spectrum (600 MHz; CDCl^; at a temperature of 333 K; chemical shifts 6 in ppm; coupling constants J in HZ): 1.09 (s, 9H: C(CH?)?; 1.19 (s, 3H: CH3) ; 1.21 (S, 3H: CH,) ; 1.27 (t, J = 7, 3H: ethyl CH,) ; 1.43 (s, 1H: OH at position 1); 1.62 (s, 3H: CH3) ; 1.68 (s, 3H: CH?) ; 1.77 and 2.63 (2 mts, 1H each: CH, at position 6); 1.86 (s, 3H: COCH,) ; 2.13 and 2.22 (2 dd, J = 16 and 9, 1H each: CH2 at position 14); 3.27 (s, 3H: OCHA) ; 3.45 and 3.68 (2 mts, 1H each: ethyl CH,) ; 3.76 (d, J = 7, 1H: H3); 3.81 (s, 3H: ArOCH^) ; 3.85 (dd, J = 11 and 7, 1H: H at position 7); 4.13 and 4.23 (2 d, J = 8.5, 1H each: CH2 at position 20); 4.58 (d, J = 4.5, 1H: H at position 2'); 4.83 (s, 1H: H at position 10); 4.90 (broad d, J = 10, 1H: H at position 5); 5.46 (d, J = 4.5, 1H: H at position 3'); 5.60 (d, J = 7 Hz, 1H: H2); 6.13 (broad t, J = 9 Hz, 1H: H13); 6.38 (s, 1H: H5'); 6.92 (d, J = 8.5, 2H: aromatic H at the ortho position with respect to OCH3) ; from 7.30 to 7.50 (mt, 9H: aromatic H at position 3' - aromatic H at the meta position with respect to OCH, and OCOChH5 H at the meta position); 7.59 (t, J = 7.5, 1H: OCOCbH; H at the para position); 8.03 (d, J = 7.5, 2H: OCOChH? H at the ortho position). A solution of 48 mg of 4a-acetoxy-2a-benzoyloxy-5/J, 20-epoxy-lO/3-ethoxy-lp1-hydroxy-7p1-methoxy-9-oxo-ll-taxen-l3a-yl (2R,4S,5R)-3-tert-butoxycarbonyl-2-(4-methoxyphenyl)-4-phenyl-l,3-oxazolidine-5-carboxylate in 0.5 cm3 of ethyl acetate and 0.004 cm1 of concentrated 37 % hydrochloric acid is kept stirring at a temperature in the region of 20°C for 1.5 hours under an argon atmosphere. The reaction mixture is then purified by preparative thin-layer chromatography: application of the crude reaction mixture to 5 Merck preparative silica gel 60F,M plates, thickness 0.5 mm, eluting with a methanol/dichloromethane (4:96 by volume) mixture. After elution of the zone corresponding to the main product with a methanol/dichloromethane (15:85 by volume) mixture, filtration through cotton wool and then evaporation of the solvents under reduced pressure (2.7 kPa) at a temperature in the region of 40°C/ 28.5 mg of 4a-acetoxy-2a-benzoyloxy-5#,20-epoxy-10)3-ethoxy-l/3-hydroxy-7/J-methoxy-9-oxo-n-taxen-l3a-yl (2R,3S)-3-tert-butoxycarbonylamino-2-hydroxy-3-phenylpropionate are obtained in the form of an ivory-coloured foam/ the characteristics of which are as follows: - 'H NMR spectrum (400 MHz; CDC1.,; chemical shifts & in ppm; coupling constants J in Hz): 1.22 (s, 3H: CH,) ; 1.25 (s, 3H: CH3) ; 1.32 (t, J = 1, 3H: ethyl CH3) ; 1.38 (s, 9H: C(CH?),; 1.64 (s, 1H: OH at position 1); 1.73 (s, 3H: CHJ ; 1.80 and 2.70 (2 mts, 1H each: CH; at position 6); 1.88 (s, 3H: CH?) ; 2.30 (mt, 2H: CH, at position 14); 2.38 (s, 3H: COCHJ ; 3.31 (s, 3H: OCHJ ; 3.44 (unres. comp., 1H: OH at position 2'); 3.50 and 3.70 (2 mts, 1H each: ethyl OCH:) ; 3.84 (d, J = 7.5, 1H: H at position 3); 3.87 (dd, J = 11 and 6.5, 1H: H at position 7); 4.18 and 4.32 (2 d, J = 8.5, 1H each: CH, at position 20); 4.64 (mt, 1H: H at position 21) ; 4.90 (s, 1H: H at position 10); 4.98 (broad d, J = 10, 1H: H at position 5); 5.28 (broad d, J = 10, 1H: H at position 3'); 5.42 (d, J = 10, 1H: CONH); 5.64 (d, J = 7.5, 1H: H at position 2); 6.22 (broad t, J = 9, 1H: H at position 13); from 7.25 to 7.45 (mt, 5H: aromatic H at position 3'); 7.50 (t, J = 7.5, 2H: OCOChH; H at the meta position); 7.62 (t, J = 7.5, 1H: OCOC,,H? H at the para position); 8.12 (d, J = 7.5, 2H: OCOC,,H, H at the ortho position). 4a-Acetoxy-2a-benzoyloxy-5/3, 20-epoxy-10/J-ethoxy-1/3,13a-dihydroxy-7y3-methoxy-9-oxo-ii-taxene (or 10/3-ethoxy-7/3-methoxy-lO-deacetoxybaccatin III) may be prepared in the following manner: 43 mg of sodium hydride at a concentration of 50 % by weight in liquid paraffin are added portionwise to a solution, maintained under an argon atmosphere/ at a temperature in the region of 0°C, of 235 mg of 4a-acetoxy-2a-benzoyloxy-5/3, 20-epoxy-l/J, 70,13a-trihydroxy-10/3-ethoxy-9-oxo-ll-taxene in 2.5 cm3 of iodomethane and 1 cm3 of dimethylformamide. After 30 minutes at a temperature in the region of 0°C, the reaction mixture is diluted with 40 cm7 of ethyl acetate, 6 cm3 of distilled water and 8 cm3 of saturated aqueous ammonium chloride solution. After settling has taken place, the organic phase is separated and washed with three times 8 cm3 of distilled water and then 8 cm3 of saturated aqueous NaCl solution, dried over magnesium sulphate, filtered through sintered glass and concentrated to dryness under reduced pressure (2.7 KPa) at a temperature in the region of 40°C. 268 mg of a yellow solid are thereby obtained, which product is purified by chromatography at atmospheric pressure on 30 g of silica (0.063-0.2 mm) contained in a column 2.5 cm in diameter (elution gradient: ethyl acetate/ dichloromethane from 0:100 to 15:85 by volume), collecting io-cm3 fractions. Fractions containing only the desired product are pooled and concentrated to dryness under reduced pressure (0.27 kPa) at 40°C for 2 hours. 380 mg of 4a-acetoxy-2a-benzoyloxy-5/3,20-epoxy-10/3-ethoxy-l/3,13a-dihydroxy-7/?-methoxy-9-oxo-n-taxene are thereby obtained in the form of a white powder, the characteristics of which are as follows: - 'H NMR spectrum (300 MHz; CDC1? with the addition of a few drops of CD3OD-d.,; chemical shifts 6 in ppm/ coupling constants J in Hz): 0.99 (s, 3H: CHJ ; 1.09 (s, 3H: CH,) ; 1.22 (t, J = 7, 3H: ethyl CH,) ; 1.62 (s, 3H: CH,) ; 1.68 and 2.66 (2 mts, 1H each: CH,6); 2.03 (s, 3H: CH,) ; 2.13 and 2.22 (2 dd, J = 16 and 9, 1H each: CH, at position 14); 2.23 (s, 3H: COCH,) ; 3.23 (s, 3H: OCH?) ; from 3.40 to 3.65 (mt, 2H: ethyl CH:) ; 3.84 (d, J = 7.5, 1H: H at position 3); 3.88 (dd, J = 10 and 6.5, 1H: H at position 7); 4.10 and 4.23 (2 d, J = 8.5, 1H each: CH: 20); 4.75 (broad t, J = 9, 1H: H at position 13); 4.90 (s, 1H: H at position 10); 4.97 (broad d, J = 10, 1H: H at position 5); 5.51 (d, J = 7.5, 1H: H at position 2); 7.42 (t, J = 7.5, 2H: DCOC,,^ H at the meta position); 7.53 (t, J = 7.5, 1H: OCOC()H; H at the para position); 8.03 (d, J = 7.5, 2H: OCOChH? H at the ortho position). 4a-Acetoxy-2a-benzoyloxy-5/3,20-epoxy-1/3,70, !3a-trihydroxy-lO/3-ethoxy-9-oxo-li-taxene (or 10/3-ethoxy-lO-deacetoxybaccatin III) may be prepared in the following manner: 9 cm3 of hydrogen fluoride/triethylamine complex (3HF.Et?N) are added to a solution, maintained under an argon atmosphere, at a temperature in the region of 20°C, of 591 mg of 4a-acetoxy-2a-benzoyloxy-5/3,20-epoxy-l/J,hydroxy-10/?-ethoxy-9-oxo-7/?, I3a-bis(triethylsilyloxy)-ll-taxene in 6 cm3 of dichloromethane. After 21 hours at a temperature in the region of 20°c, the reaction mixture is diluted with 40 cm7 of dichloromethane and poured into a suspension of 40 cm1 of supersaturated aqueous sodium hydrogen carbonate solution maintained at a temperature in the region of 0°C. After dilution with 10 cm3 of distilled water and when settling has taken place, the aqueous phase is separated and re-extracted with twice 20 cm3 of diethyl ether. The organic phases are combined, washed with 20 cm* of distilled water and 20 cm3 of saturated aqueous sodium chloride solution, dried over magnesium sulphate, filtered through magnesium sulphate and concentrated to dryness under reduced pressure (2.7 kPa) at a temperature in the region of 40°C. 370 mg of a pale yellow foam are thereby obtained, which product is purified by chromatography at atmospheric pressure on 35 g of silica (0.063-0.2 mm) contained in a column 2.5 cm in diameter, eluting with a methanol/dichloromethane (2:98 by volume) mixture and collecting l5-cm? fractions. Fractions containing only the desired product are pooled and concentrated to dryness under reduced pressure (2.7 kPa) at 40°C for 2 hours. 236.2 mg of 4a-acetoxy-2a-benzoyloxy-5/2, 20- epoxy-1/3, 7/3, 13a-trihydroxy-lO/3-ethoxy-9-oxo-li-taxene are thereby obtained in the form of a white solid, the characteristics of which are as follows: - 'H NMR spectrum (400 MHz; CDC13: chemical shifts S in ppm, coupling constants J in Hz): 1.08 (s, 3H: CH3) ; 1.19 (s, 3H: CH,) ; 1.29 (t, J = 7.5, 3H: ethyl CH3) ; 1.38 (d, J - 9, 1H: OH at position 7); 1.59 (s, 1H: OH at position 1); 1.69 (s, 3H: CH,) ; 1.82 and 2.62 (2 mts, 1H each: CH, at position 6); 2.02 (d, J = 5, 1H: OH at position 13); 2.08 (s, 3H: CH,) ; 2.30 (s, 3H: COCHJ ; 2.32 (d, J = 9, 2H: CH2 at position 14); 3.56 and 3.67 (2 mts, 1H each: ethyl OCH3) ; 3.98 (d, J = 7, 1H: H at position 3); 4.18 and 4.33 (2 d, J = 8.5 Hz, 1H each: CH:20); 4.30 (mt, 1H: H7); 4.90 (mt, 1H: H at position 13); 4.99 (dd, J = 10 and 1.5, 1H: H at position 5); 5.05 (s, 1H: H at position 10); 5.66 (d, J = 7, 1H: H at position 2); 7.49 (t, J = 7.5, 2H: OCOChH; H at the meta position); 7.63 (t, J = 7.5, 1H: OCOChH? H at the para position); 8.12 (d, J = 7.5, 2H: OCOC,,H; H at the ortho position). 4o-Acetoxy-2a-benzoyloxy-5#, 20-epoxy-l/J-hydroxy-lO/3-ethoxy-9-oxo-7/3,13a-bis (triethylsilyloxy) -ll-taxene (or !0/3-ethoxy-lO-deacetoxy-7,13-bis(triethylsilyl)baccatin III) may be prepared in the following manner: 93 mg of sodium hydride at a concentration of 50 % by weight of liquid paraffin are added portionwise to a solution, maintained under an argon atmosphere, at a temperature in the region of 20°C/ of 1 g of 4a-acetoxy-2a-benzoyloxy-5|3,20-epoxy-l/3, iO/2-dihydroxy-9-oxo-7/3,13a-bis (triethylsilyloxy)-11-taxene in 3 cm3 of iodoethane and 4 cm3 of dimethylformamide. The solution is kept stirring for 17 hours at a temperature in the region of 20°C, and 93 mg of sodium hydride at a concentration of 50 % by weight in liquid paraffin is then added portionwise. After 50 minutes at a temperature in the region of 20°C/ the reaction mixture is diluted with 100 cm3 of ethyl acetate and 10 cm3 of saturated aqueous ammonium chloride solution. The organic phase is separated after settling has taken place and washed with six times 10 cm3 of distilled water and then 10 cm3 of saturated aqueous sodium chloride solution, dried over magnesium sulphate, filtered through sintered glass and concentrated to dryness under reduced pressure (2.7 kPa) at a temperature in the region of 40°C. 1.2 g of a yellow foam are thereby obtained, which product is purified by chromatography at atmospheric pressure on 150 g of silica (0.063-0.2 mm) contained in a column 3.5 cm in diameter, eluting with an ethyl acetate/dichloromethane (2:98, then 5:95 by volume) mixture and collecting 15-cm3 fractions. Fractions containing only the desired products are pooled and concentrated to dryness under reduced pressure (0.27 kPa) at 40°C for 2 hours. 379.2 mg of 4a-acetoxy-2a-benzoyloxy-5/3,20-epoxy-1/3, lO/J-dihydroxy-9-oxo-7/3, 13a-bis (triethylsilyloxy) -11- taxene are thereby obtained in the form of a pale yellow foam and 430 mg of 4a-acetoxy-2a-benzoyloxy-5/3,20-epoxy-i/3-hydroxy-10/J-ethoxy-9-oxo-7/3, 13a-bis(triethylsilyloxy)-ll-taxene are thereby obtained in the form of a white foam/ the characteristics of which are as follows: - 'H NMR spectrum (400 MHz; CDC1?; chemical shifts S in ppm, coupling constants J in Hz): 0.57 and 0.70 (2 rots, 6H each; ethyl CH2) ; 0.97 and 1.03 (2 t, J = 7.5, 9H each: ethyl CH,) ; 1.13 (s, 3H: CH,) ; 1.20 (s, 3H: CH?) ; 1.29 (t, J = 7.5, 3H: CH3 of ethoxy at position 10); 1.58 (s, 1H: OH at position 1); 1.66 (s, 3H: CH?) ; 1.89 and 2.58 (2 mts, 1H each: CH: at position 2); 2.03 (s, 3H: CH3) ; 2.13 and 2.23 (2 dd, J = 16 and 9, 1H each: CH, at position 14); 2.30 (s, 3H: COCHJ ; 3.53 (mt, 2H: CH: of ethoxy at position 10); 3.84 (d, J = 7, 1H: H at position 3); 4.15 and 4.30 (2 d, J = 8.5, 1H each: CH2 at position 20); 4.43 (dd, J = 11 and 6.5, 1H: H at position 7); from 4.90 to 5.00 (mt, 2H: H at position 13 and H at position 5); 5.01 (s, 1H: H at position 10); 5.61 (d, J = 7, 1H: H at position 2); 7.48 (t, J = 7.5, 2H: OCOC6H? H at the meta position); 7.61 (t, J = 7.5, 1H: OCOC^ H at the para position); 8.10 (d, J = 7.5, 2H: OCOC6H5 H at the ortho position). EXAMPLE 4 65 mg of dicyclohexylcarbodiimide and then 7 mg of 4-(N,N-dimethylaminopyridine are added successively at a temperature in the region of 20°C to a suspension containing 115 mg of 4a-acetoxy-2a-benzoyloxy-5/3,20-epoxy-10/J-(l-propyl)oxy-l/3,13a-dihydroxy-7/?-methoxy-9-oxo-ll-taxene and 100 mg of (2R,4S,5R)-3-tert-butoxycarbonyl-2-(4-methoxyphenyl)-4-phenyl-l,3-oxazolidine-5-carboxylic acid in l cm3 of anhydrous toluene. The suspension obtained is stirred at a temperature in the region of 20°c under an argon atmosphere for 1 hour, and then purified by direct application to a column for chromatography at atmospheric pressure on 30 g of silica (0.063-0.2 mm) contained in a column 2.5 cm in diameter (elution gradient: ethyl acetate/dichloromethane from 2:98 to 10:90 by volume), collecting 10-cm3 fractions. Fractions containing only the desired product are pooled and concentrated to dryness under reduced pressure (2.7 kPa) at 40°C for 2 hours. 276.2 mg of a white solid are thereby obtained, which product is purified by preparative thin-layer chromatography: 10 Merck preparative silica gel 60F2;;4 plates, thickness 0.5 mm, application in solution in dichloromethane, eluting with a methanol/dichloromethane (3:97 by volume) mixture. After elution of the zones corresponding to the main products with a raethanol/dichloromethane (15:85 by volume) mixture, filtration through cotton wool and then evaporation of the solvents under reduced pressure (2.7 kPa) at a temperature in the region of 40°C, 84.8 mg of 4a-acetoxy-2a-benzoyloxy-5/J,20-epoxy-10/3- (l-propyl) oxy-l|3-hydroxy-7/J-methoxy-9-oxo-ll-taxen- 13ct-yl (2R,4S,5R) -3-tert-butoxycarbonyl-2- (4-methoxyphenyl)-4-phenyl-l,3-oxazolidine-5-carboxylate are obtained in the form of a white foam, the characteristics of which are as follows: - 'H NMR spectrum (300 MHz; CDCL,; chemical shifts S in ppm; coupling constants J in Hz): 0.97 (t, J = 7, 3H: propyl CH3) ; 1.07 (s, 9H: C(CH3)3); 1.19 (s, 6H: CH?) ; from 1.50 to 1.80 (mt, 3H: OH at position 1 and central CH; of propyl); 1.60 (s, 3H: CH,) ; 1.70 (s, 3H: CH-,) ; 1.78 and 2.63 (2 mts, 1H each: CH, at position 6); 1.82 (unres. comp. 3H: COCH() ; 2.07 and 2.19 (2 dd, J = 16 and 9, 1H each: CH, at position 14); 3.26 (s, 3H: OCH-,) ; 3.30 and 3.58 (2 mts, 1H each: propyl OCH:) ; 3.73 (d, J = 7.5, 1H: H at position 3); 3.81 (s, 3H: ArOCH,) ; 3.81 (mt, 1H: H at position 7); 4.09 and 4.23 (2 d, J = 8.5, 1H each: CH, at position 20); 4.57 (d, J = 4.5, 1H: H at position 2'); 4.79 (s, 1H: H at position 10); 4.90 (broad d, J = 10, 1H: H at position 5); 5.40 (unres. comp. 1H: H at position 3'); 5.58 (d, J = 7.5, 1H: H at position 2); 6.13 (broad t, J = 9, 1H: H at position 13); 6.40 (spread unres. comp. 1H: H at position 5'); 6.92 (d, J = 8.5, 2H: aromatic H at the ortho position with respect to OCH-,) ; from 7.30 to 7.60 (mt, 9H: aromatic H at position 3' - aromatic H at the meta position with respect to OCH3 and OCOC(,H:; meta H) ; 7.63 (t, J = 7.5, 1H: OCOC6H;; H at the para position); 8.03 (d, J = 7.5, 2H: OCOC6H? H at the ortho position). 4a-Acetoxy-2a-benzoyloxy-5p1, 20-epoxy-10/3- (1- propyl)oxy-l/3-hydroxy-7/3-methoxy-9-oxo-l l-taxen-13cr-yl (2R,3S)-3-tert-butoxycarbonylamino-2-hydroxy-3-phenylpropionate may be prepared in the following manner: A solution of 84 mg of 4a-acetoxy-2a- benzoyloxy-5/2,20-epoxy-10/3-(i-propyl)oxy-l/3-hydroxy-7/3-methoxy-9-oxo-ll-taxen-l3a-yl (2R,4S,5R)-3-tert-butoxy-carbonyl-2-(4-methoxyphenyl)-4-phenyl-l,3-oxazolidine-5-carboxylate in 0.84 cm? of ethyl acetate and 0.0071 cm3 of concentrated 37 % hydrochloric acid is kept stirring at a temperature in the region of 20°C for 1 hour under an argon atmosphere. The reaction mixture is then purified by preparative thin-layer chromatography: application of the crude reaction mixture to 6 Merck preparative silica gel 60F^4 plates, thickness 0.5 nun, eluting with a methanol/acetonitrile/ dichloromethane (3:7:90 by volume) mixture. After elution of the zone corresponding to the main product with a methanol/dichloromethane (15:85 by volume) mixture, filtration through cotton wool and then evaporation of the solvents under reduced pressure (2.7 kPa) at a temperature in the region of 40°C, 27 mg of 4a-acetoxy-2a-benzoyloxy-5/J,20-epoxy-10/3- (1-propyl)oxy-l/3-hydroxy-7/3-methoxy-9-oxo-l l-taxen-13a-yl (2R,3S)-3-tert-butoxycarbonylamino-2-hydroxy-3-phenyl-propionate are obtained in the form of a white foam, the characteristics of which are as follows: - 'H NMR spectrum (400 MHz; CDC1?; chemical shifts S in ppm; coupling constants J in Hz): 0.99 (t, J = 7, 3H: propyl CHO ; 1.22 (s, 3H: CH3) ; 1.25 (s, 3H: CH,) ; 1.38 (s, 9H: C(CH3)3; 1.64 (s, 1H: OH at position 1); 1.69 (mt, 2H: central CH2 of propyl); 1.73 (s, 3H: CH3) ; 1.80 and 2.70 (2 mts, 1H each: CH2 at position 6); 1.88 (s, 3H: CH3) ; 2.30 (mt, 2H: CH, at position 14); 2.38 (s, 3H: COCH,) ; 3.31 (s, 3H: OCH3) ; 3.36 and 3.64 (2 mts, 1H each: propyl OCH2) ; 3.44 (unres. comp. 1H: OH at position 2'); 3.84 (d, J = 7.5, Hz, 1H: H at position 3); 3.87 (dd, J = 11 and 6.5, 1H: H at position 7); 4.18 and 4.30 (2 d, J = 8.5, 1H each: CH; at position 20); 4.64 {mt, 1H: H at position 2'); 4.89 (s, 1H: H at position 10); 4.98 (broad d, J = 10, 1H: H at position 5); 5.28 (broad d, J = 10, 1H: H at position 3'); 5.42 (d, J = 10, 1H: CONH); 5.64 (d, J = 7.5, 1H: H at position 2); 6.22 (broad t, J = 9, 1H: H at position 13); from 7.25 to 7.45 (mt, 5H: aromatic H at position 3'); 7.50 (t, J = 7.5, 2H: OCOC,,H5 H at the meta position); 7.61 (t, J = 7.5, 1H: OCOCt)H, H at the para position); 8.12 (d, J = 7.5, 2H: OCOC,,H? H at the ortho position). 4a-Acetoxy-2a-benzoyloxy-5/3, 20-epoxy-10/J- (1-propyl) oxy-l/3, l3a-dihydroxy-7/3-methoxy-9-oxo-n-taxene (or 10/3- (l-propyl) oxy-7/J-methoxy-lO-deacetoxybaccatin III) may be prepared in the following manner: 30 mg of sodium hydride at a concentration of 50 % by weight in liquid paraffin are added portionwise to a solution, maintained under an argon atmosphere, at a temperature in the region of 0°C/ of 165 mg of 4a-acetoxy-2a-benzoyloxy-5/3,20-epoxy-i/3,7/i, I3a-trihydroxy-10/J-(l-propyl)oxy-9-oxo-il-taxene in 1.7 cm3 of iodomethane and 1 cm3 of dimethylformamide. After 30 minutes at a temperature in the region of 0°C, the reaction mixture is diluted with 40 cm3 of ethyl acetate, 5 cm3 of distilled water and "1 cm3 of saturated aqueous ammonium chloride solution. After settling has taken place, the organic phase is separated and washed with three times 7 cm3 of distilled water and then 1 cm3 of saturated aqueous sodium chloride solution, dried over magnesium sulphate, filtered through sintered glass and concentrated to dryness under reduced pressure (2.7 kPa) at a temperature in the region of 40°C. 224 mg of the yellow solid are thereby obtained, which product is purified by chromatography at atmospheric pressure on 20 g of silica (0.063-0.2 mm) contained in a column 2.5 cm in diameter (elution gradient: ethyl acetate/dichloromethane from 0:100 to 15:85 by volume), collecting 10-cm3 fractions. Fractions containing only the desired product are pooled and concentrated to dryness under reduced pressure (0.27 kPa) at 40°C for 2 hours. 117.5 mg of 4a-acetoxy-2a-benzoyloxy-5/J,20-epoxy-lO/3-(l-propyl)oxy-l/3,13a-dihydroxy-70-methoxy-9-oxo-ii-taxene are thereby obtained in the form of a white foam, the characteristics of which are as follows: - 'H NMR spectrum (300 MHz; CDC13; chemical shifts 5 in ppm, coupling constants J in Hz): 0.98 (t, J = 7, 3H: propyl CH3) ; 1.05 (s, 3H: CH3) ; 1.19 (s, 3H: CH3) ; from 1.60 to 1.80 (mt, 2H: central CH, of propyl); from 1.65 to 1.85 and 2.66 (2 mts, 1H each: CH, at position 6) ; 1.72 (S, 3H: CH3) ; 2.10 (s, 3H: CH-,) ; from 2.05 to 2.35 (mt, 2H: CH2 at position 14); 2.28 (s, 3H: COCH3) ; 3.32 (s, 3H: OCH3) ; 3.45 and 3.65 (2 mts, 1H each: propyl OCH:); 3.92 (d, J = 7.5, 1H: H3); 3.93 (dd, J = 11 and 6, 1H: H at position 7); 4.16 and 4.32 (2 d, J = 8.5, 1H each: CH, at position 20); 4.90 (mt, 1H: H at position 13); 4.94 (s, 1H: H at position 10); 5.03 (broad d, J = 10, 1H: H at position 5); 5.60 (d, J = 7.5, 1H: H at position 2); 7.48 (t, J = 7.5, 2H: OCOC6H; H at the meta position); 7.62 (t, J = 7.5, 1H: OCOC6H5 H at the para position); 8.11 (d, J = 7.5, 2H: OCOC6H? H at the ortho position). 4a-Acetoxy-2a-benzoyloxy-5/3, 20-epoxy- 1/3, 7/3, !3a-trihydroxy-lO/3- (1-propyl) oxy-9-oxo-ll-taxene (or 10/3-(l-propyl) oxy-10-deacetoxybaccatin III) may be prepared in the following manner: 8.75 cm3 of hydrogen fluoride/triethylamine complex (3HF.Et3N) are added to a solution, maintained under an argon atmosphere, at a temperature in the region of 20°C, of 585 mg of 4a-acetoxy-2a-benzoyloxy-5/3, 20-epoxy-l/3-hydroxy-10/J- (1-propyl) oxy-9-oxo-7/3,13a-bis(triethylsilyloxy)-11-taxene in 6 cm3 of dichloromethane. After 24 hours at a temperature in the region of 20°C, the reaction mixture is diluted with 30 cm3 of dichloromethane and poured into a suspension of 30 cm3 of supersaturated aqueous sodium hydrogen carbonate solution maintained at a temperature in the region of 0°C. After dilution with 10 cm3 of distilled water and when settling has taken place, the aqueous phase is separated and re-extracted with twice 20 cm3 of diethyl ether. The organic phases are combined, washed with 20 cm' of distilled water and 20 cm3 of saturated aqueous sodium chloride solution, dried over magnesium sulphate, filtered through magnesium sulphate and concentrated to dryness under reduced pressure (2.7 kPa) at a temperature in the region of 40°C. 500 mg of a pale yellow foam are thereby obtained, which product is purified by chromatography at atmospheric pressure on 40 g of silica (0.063-0.2 mm) contained in a column 2.5 cm in diameter, eluting with a methanol/dichloromethane (2:98 by volume) mixture and collecting 15-cm3 fractions. Fractions containing only the desired product are pooled and concentrated to dryness under reduced pressure (2.7 kPa) at 40°C for 2 hours. 373.8 mg of 4a-acetoxy-2a-benzoyloxy-5/-(, 20-epoxy-1/J, 7/3,I3a-trihydroxy-10#- (i-propyl) oxy-9-oxo-ll-taxene are thereby obtained in the form of a white solid, the characteristics of which are as follows: - *H NMR spectrum (300 MHz; CDC13; chemical shifts 6 in ppm, coupling constants J in Hz): 0.95 (t, J = 7, 3H: propyl CH?) ; 1.06 (s, 3H: CH,) ; 1.22 (s, 3H: CHO ; 1.45 (d, J = 7.5, 1H: OH at position 7); from 1.60 to 1.80 (mt, 2H: central CH: of propyl) ; 1.67 (s, 3H: CH,) ; 1.83 and 2.62 (2 mts, 1H each: CH: at position 6); 2.05 (s, 3H: CH3) ; 2.05 (mt, 1H: OH at position 13); 2.27 (limiting AB, 2H: CH-, at position 4); 2.28 (s, 3H: COCH3) ; 3.40 and 3.57 (2 mts, 1H each: propyl OCH2) ; 3.97 (d, J = 7.5, 1H: H at position 3); 4.15 and 4.30 (2 d, J = 8.5, 1H each: CH2 at position 20); 4.28 (mt, 1H: H at position 7); 4.90 (mt, 1H: H at position 13); 4.97 (broad d, J = 10, 1H: H at position 5); 5.03 (s, 1H: H at position 10); 5.65 (d, J = 7.5, IE: H at position 2); 7.50 (t, J = 7.5, 2H: OCOC,,H- H at the meta position); 7.60 (t, J = 7.5, 1H: OCOC,,H; H at the para position); 8.00 (d, J = 7.5, 2H: OCOC,,H? H at the ortho position). 4a-Acetoxy-2a-benzoyloxy-5/3, 2 O-epoxy-1/3-hydroxy-10/j- (1-propyl) oxy-9-oxo-7,j, I3a-bis (triethylsilyloxy)-11-taxene (or 10/i-(l-propyl) oxy-10-deacetoxy-7,13-bis(triethylsilyl)baccatin III) may be prepared in the following manner: 93 mg of sodium hydride at a concentration of 50 % by weight in liquid paraffin are added portionwise to a solution, maintained under an argon atmosphere, at a temperature in the region of 20°C, of 1 g of 4a-acetoxy-2a-ben2oyloxy-5/3,20-epoxy-l/3,10/3-dihydroxy-9-oxo-7/3,13a-bis (triethylsilyloxy)-11-taxene in 3 cm? of iodoethane and 4 cnv1 of dimethylformamide. The solution is kept stirring for 19 hours at a temperature in the region of 20°C, and 93 mg of sodium hydride at a concentration of 50 % by weight in liquid paraffin are then added portionwise. After 3 hours at a temperature in the region of 20°C/ the reaction mixture is diluted with 100 cm3 of ethyl acetate and 10 cnv of saturated aqueous ammonium chloride solution. The organic phase is separated after settling has taken place and washed with six times 10 cm3 of distilled water and then 10 cm3 of saturated aqueous sodium chloride solution/ dried over magnesium sulphate, filtered through sintered glass and concentrated to dryness under reduced pressure (2.7 kPa) at a temperature in the region of 40°C. 1.32 g of a pale yellow foam are thereby obtained/ which product is purified by chromatography at atmospheric pressure on 150 g of silica (0.063-0.2 mm) contained in a column 3.5 cm in diameter, eluting with an ethyl acetate/dichloromethane (2:98, then 5:95 by volume) mixture and collecting 15-cm3 fractions. Fractions containing only the desired products are pooled and concentrated to dryness under reduced pressure (0.27 kPa) at 40°C for 2 hours. 376.3 mg of 4a-acetoxy-2a-benzoyloxy-5/3,20-epoxy-1/3 / 10/3-dihydroxy-9-oxo-7/3,13a-bis (triethylsilyloxy) -11-taxene are thereby obtained in the form of a pale yellow foam and 395.3 mg of 4a-acetoxy-2a-benzoyloxy-5/3, 20-epoxy-l/3-hydroxy-lo/2- (1-propyl) oxy-9-oxo-7/J, I3a-bis(triethylsilyloxy)-ll-taxene are thereby obtained in the form of a pale yellow foam/ the characteristics of which are as follows: - 'H NMR spectrum (400 MHz; CDC13; chemical shifts S in ppm; coupling constants J in Hz): 0.57 and 0.70 (2 mts, 6H each: ethyl CH,) ; 0.94 and 1.03 (2 t, J = 7.5, 9H each: ethyl CH?) ; 0.94 (t, J = 7.5, 3H: propyl CH-,) ; 1.14 (s, 3H: CH3) ; 1.21 (s, 3H: CH?) ; 1.67 (s, 3H: CH3) ; 1.69 (mt, 2H: central CH2 of propyl); 1.88 and 2.48 (2 mts, 1H each: CH, at position 6); 2.03 (s, 3H: CH3) ; 2.13 and 2.23 (2 dd, J = 16 and 9, 1H each: CH, at position 14); 2.30 (s, 3H: COCH^) ; 3.40 (mt, 2H: propyl OCH,) ; 3.84 (d, J = 7.5, 1H: H at position 3); 4.16 and 4.30 (2 d, J = 8.5, 1H each: CH, at position 20); 4.44 (dd, J = 11 and 6.5, 1H: H at position 7); 4.96 (broad d, J = 10 Hz, 1H: H5); 4.97 (s, 1H: H 10); 4.99 (broad t, J = 9Hz, 1H: H at position 13); 5.62 (d, J = 7.5, 1H: H at position 2); 7.48 (t, J = 7.5, 2H: OCOC6H: H at the meta position); 7.60 (t, J = 7.5, 1H: OCOCt)H; H at the para position); 8.10 (d, J = 7.5, 2H: OCOC,,H; H at the ortho position). The compounds of formula (I) in which Z represents a radical of formula (II) manifest significant inhibitory activity with respect to abnormal cell proliferation, and possess therapeutic properties permitting the treatment of patients having pathological conditions associated with abnormal cell proliferation. The pathological conditions include the abnormal cell proliferation of malignant or non-malignant cells of various tissues and/or organs, comprising, without implied limitation, muscle, bone or connective tissue, the skin, brain, lungs, sex organs, the lymphatic or renal systems, mammary or blood cells/ liver, the digestive system, pancreas and thyroid or adrenal glands. These pathological conditions can also include psoriasis, solid tumours, cancers of the ovary/ breast/ brain/ prostate/ colon, stomach/ kidney or testicles/ Kaposi's sarcoma/ cholangiocarcinoma/ choriocarcinoma/ neuroblastoma/ Wilms' tumour, Hodgkin's disease, melanoma, multiple myeloma, chronic lymphocytic leukaemia and acute or chronic granulocytic lymphoma. The compounds are especially useful for the treatment of cancer of the ovary. The compounds may be used to prevent or delay the appearance or reappearance of the pathological conditions, or to treat these pathological conditions. The compounds may be administered to a patient according to different dosage forms suited to the chosen administration route, which is preferably the parenteral route. Parenteral administration comprises intravenous, intraperitoneal, intramuscular or subcutaneous administration. Intraperitoneal or intravenous administration is more especially preferred. The present invention also comprises pharmaceutical compositions containing at least one compound of formula (I) in which Z represents a radical of formula (II), in a sufficient amount suitable for use in human or veterinary therapy. The compositions may be prepared according to the customary methods, using one or more pharmaceutically acceptable adjuvants, vehicles or excipients. Suitable vehicles include diluents, sterile aqueous media and various non-toxic solvents. Preferably, the compositions take the form of aqueous solutions or suspensions, injectable solutions which can contain emulsifying agents, colourings, preservatives or stabilizers. However, the compositions can also take the form of tablets, pills, powders or granules which can be administered orally. The choice of adjuvants or excipients may be determined by the solubility and the chemical properties of the product, the particular mode of administration and good pharmaceutical practice. For parenteral administration, sterile, aqueous or non-aqueous solutions or suspensions are used. For the preparation of non-aqueous solutions or suspensions, natural vegetable oils such as olive oil, sesame oil or liquid petroleum, or injectable organic esters such as ethyl oleate, may be used. The sterile aqueous solutions can consist of a solution of a pharmaceutically acceptable salt dissolved in water. The aqueous solutions are suitable for intravenous administration provided the pH is appropriately adjusted and the solution is made isotonic, for example with a sufficient amount of sodium chloride or glucose. The sterilization may be carried out by heating or by any other means which does not adversely affect the composition. It is clearly understood that all the compounds in the compositions according to the invention must be pure and non-toxic in the amounts used. The compositions can contain at least 0.01% of therapeutically active compound. The amount of active compound in a composition is such that a suitable dosage can be prescribed. Preferably, the compositions are prepared in such a way that a single dose contains from o.oi to 1000 mg approximately of active compound for parenteral administration. The therapeutic treatment may be performed concurrently with other therapeutic treatments including antineoplastic drugs, monoclonal antibodies, immunotherapy or radiotherapy or biological response modifiers. The response modifiers include, without implied limitation, lymphokines and cytokines such as interleukins, interferons (a, 0 or 6) and TNF. Other chemotherapeutic agents which are useful in the treatment of disorders due to abnormal cell proliferation include, without implied limitation, alkylating agents, for instance nitrogen mustards such as mechlorethamine, cyclophosphamide, melphalan and chlorambucil, alkyl sulphonates such as busulfan, nitrosoureas such as carmustine, lomustine, semustine and streptozocin, triazenes such as dacarbazine, antimetabolites such as folic acid analogues, for instance methotrexate, pyrimidine analogues such as fluorouracil and cytarabine/ purine analogues such as mercaptopurine and thioguanine, natural products, for instance vinca alkaloids such as vinblastine, vincristine and vindesine, epipodophyllotoxins such as etoposide and teniposide, antibiotics such as dactinomycin, daunorubicin, doxorubicin, bleomycin, plicamycin and mitomycin, enzymes such as L-asparaginase, various agents such as coordination complexes of platinum, for instance cisplatin, substituted ureas such as hydroxyurea, methylhydrazine derivatives such as procarbazine, adrenocortical suppressants such as mitotane and aminoglutethimide, hormones and antagonists such as adrenocorticosteroids such as prednisone, progestins such as hydroxyprogesterone caproate, methoxyprogesterone acetate and megestrol acetate, oestrogens such as diethylstilboestrol and ethynyloestradiol, antioestrogens such as tamoxifen, and androgens such as testosterone propionate and fluoxymesterone. The active compounds are used at dosages which permit a prophylactic treatment or a maximum therapeutic response. The dosages vary according to the administration form, the particular product selected and features distinctive to the subject to be treated. In general, the dosages are those which are therapeutically effective for the treatment of disorders due to abnormal cell proliferation. The active compound according to the invention may be administered as often as necessary to obtain the desired therapeutic effect. Some patients may respond rapidly to relatively high or low dosages, and then require low or zero maintenance dosages. Generally/ low dosages will be used at the beginning of the treatment and, if necessary, increasingly stronger doses will be administered until an optimum effect is obtained. For other patients, it may be necessary to administer maintenance dosages 1 to 8 times a day, and preferably 1 to 4 times, according to the physiological requirements of the patient in question. It is also possible that some patients may require the use of only one to two daily administrations. In man, the dosages are generally between 0.01 and 200 mg/kg. For intraperitoneal administration, the dosages will generally be between 0.1 and 100 mg/kg, preferably between 0.5 and 50 mg/kg and still more specifically between 1 and 10 mg/kg. For intravenous administration, the dosages are generally between 0.1 and 50 mg/kg, preferably between 0.1 and 5 mg/kg and still more specifically between 1 and 2 mg/kg. It is understood that, in order to choose the most suitable dosage, account should be taken of the administration route, the patient's weight, general state of health and age and all factors which may influence the efficacy of the treatment. The example which follows illustrates a composition according to the invention. EXAMPLE 5 40 mg of the product obtained in Example l are dissolved in 1 cm3 of Emulphor EL 620 and I cm3 of ethanol, and the solution is then diluted by adding 18 cm3 of physiological saline. The composition is administered by perfusion over 1 hour by introduction in physiological solution. WE CLAIM: 1 A taxoid of formula: (Formula Removed) which: Z represents a hydrogen atom or a radical of formula: (Formula Removed) in which: R1represents a benzoyl radical or a radical R2-O-CO- in which R2 represents a tert-butyl radical and R3 represents an isobutyl, isobutenyl, butenyl, cyclohexyl, phenyl, 2-furyl, 3-furyl, 2-thienyl, 3-thienyl, 2-thiazolyl, 4-thiazolyl or 5-thiazolyl radical, and R4 and R5, which may be identical or different, each represent a methoxy, ethoxy or propoxy radical. 2. A process for preparing a taxoid as claimed in claim 1 in which Z represents a radical of formula (D) and R4 and R5 are as defined in claim 1, which comprises treating a compound of formula: (Formula Removed) in which R1and R3 are as defined in claim 1 and R6 and R7 are as defined in claim 2, with a compound of formula: (R)3Si-Hal (X) in which the symbols R, which may be identical or different, represent an alkyl radical ccmiaining 1 to 6 carbon atoms, optionally substituted by a phenyl radical, or a cycloalkyl radical cemtaining 3 to 6 carbon atoms or a phenyl radical, to obtain a compound of formula: (Formula Removed) in which R, R1, R3, R6 and R7 are as defined above, which is then functionalized at the 10-position using a compound of formula: (Formula Removed) in which R4 represents a radical such that R4-O is identical to R4 as defined above and X1 represents a halogen atom or a reactive ester residue, to give a compound of formula: (Formula Removed) in which R, R1, R3 R4, R6 and R7 are as defined above, the silyl protective group of which is then replaced by a hydrogen atom to give a compound of formula: (Formula Removed) which, by the action of a compound of formula (XV), yields a compound of formula (V), (Formula Removed) the heterocycle formed by R6 and R7 of which is replaced by hydrogen atom(s) to give a compound of formula (I) in which Z represents a radical of formula (II). 3. A taxoid as claimed in claim 1 which is 4a-acetoxy-2a-benzoyloxy-5β,20-epoxy-1β-hydroxy-7β,10β-dimethoxy-9-oxo-l l-taxen-13α-yl (2R,3S)-3-tert- butoxycarbonylamino-2-hydroxy-3-phenylpropioriate. 4. A taxoid as claimed in claim 1 in which Z represents a radical of formula (II), as and when used as a pharmaceutical composition together with a pharmaceutically acceptable carrier or coating as herein before described. 5. A taxoid as claimed in claim 1 substantially as hereinbefore described. 6. A process as claimed in claim 2 substantially as hereinbefore described with reference to the foregoing examples. 7. A taxoid as claimed in claim 1 when prepared by a process as claimed in claim 2, or 6.

Documents:

635-DEL-1996-Abstract-(17-10-2008).pdf

635-DEL-1996-Abstract-28-03-2008.pdf

635-del-1996-abstract.pdf

635-DEL-1996-Claims-(17-10-2008).pdf

635-DEL-1996-Claims-28-03-2008.pdf

635-del-1996-claims.pdf

635-del-1996-complete specification (granted).pdf

635-DEL-1996-Correspondence-Others-(15-10-2008).pdf

635-DEL-1996-Correspondence-Others-(16-10-2008).pdf

635-DEL-1996-Correspondence-Others-27-05-2008.pdf

635-DEL-1996-Correspondence-Others-28-03-2008.pdf

635-del-1996-correspondence-others.pdf

635-del-1996-description (complete)-17-10-2008.pdf

635-del-1996-description (complete).pdf

635-DEL-1996-Description (Complete)28-03-2008.pdf

635-DEL-1996-Form--1-28-03-2008.pdf

635-DEL-1996-Form--2-28-03-2008.pdf

635-DEL-1996-Form-1-(17-10-2008).pdf

635-del-1996-form-1.pdf

635-DEL-1996-Form-13-(15-10-2008).pdf

635-del-1996-form-13.pdf

635-DEL-1996-Form-18-28-03-2008.pdf

635-del-1996-form-18.pdf

635-DEL-1996-Form-2-(17-10-2008).pdf

635-del-1996-form-2.pdf

635-del-1996-form-29.pdf

635-DEL-1996-Form-3-28-03-2008.pdf

635-del-1996-form-4.pdf

635-del-1996-form-6.pdf

635-DEL-1996-GPA-28-03-2008.pdf

635-del-1996-gpa.pdf

635-DEL-1996-Others Document-2--27-05-2008.pdf

635-DEL-1996-Others Document-3-27-05-2008.pdf

635-DEL-1996-Others Document-4-27-05-2008.pdf

635-DEL-1996-Others Document-5-27-05-2008.pdf

635-DEL-1996-Others Document-6-27-05-2008.pdf

635-DEL-1996-Others Document-7-27-05-2008.pdf

635-DEL-1996-Others Document1-27-05-2008.pdf

635-DEL-1996-Petition-137-28-03-2008.pdf

635-DEL-1996-Petition-138-28-03-2008.pdf

abstract.jpg