GB2296239A - Taxane derivatives modified at 6 and 7 positions for use as antitumour agents - Google Patents

Abstract

Taxane derivatives which are modified at the 6 and 7 positions of the taxane derivative skeleton (taxol numbering) and are of formula I: <IMAGE> [wherein R3 represents hydrogen atom, hydroxy group or a group of formula -OCOR', -OR', -OSO2R', -OCONR'R", -OCONHR', or OCOOR'; R4 is -COR''' or -COOR'''; R', R" and R''' each independently represents C1-C6 alkyl, C2-C6 alkenyl, C3-C6 cycloalkyl, C2-C6 alkynyl of a phenyl group (optionally substituted with one, two or three, same or different substituents selected from halogen atom, C1-C6 alkyl, C1-C6 alkoxy, and CF3 groups); and either: (i) R1 together with R2 represents an oxygen atom or a group of the formula >N-Z or >CH-Z or (ii) R1 represents a hydroxy group and R2 represents a hydrogen atom, azido group or a group of formula NR5R6 or (iii) R1 represents an azido group or a group of formula NR5R6 and R2 represents a hydroxy group, wherein Z is a hydrogen atom, carboxy or a C1-C6 alkoxycarbonyl group and R5 and R6 each independently represents a hydrogen atom or a C1-C6 alkyl, C1-C8 alkanoyl or C7-C11 aroyl group] and pharmceutically acceptable salts thereof are allowed with antitumor activity.

Description

TAXANE DERIVATIVES The present invention is directed to new taxane derivatives endowed with antitumor activity, to a process for their preparation and to pharmaceutical compositions containing them.

The taxane family of diterpenes includes Paclitaxel (also named taxol in several publications), isolated and characterized from an extract of bark of Taxus brevifolia L., and Cephalomannine (see J.Chem.Soc. Chem.Comm. 102, 1979); other taxane analogues are also known and were prepared by semisynthesis starting from l0-deacetyl baccatin III, extracted from the needles of Taxus baccata L. (see Wani et al., J.Am.Chem.Soc. 93, 2325 , 1971; Lovelle et al., Proc.Am.Assoc.Cancer Res. 31, 417, 1990).

Particularly, taxol is a very potent anticancer drug and is already applied with success to the treatment of platinumresistant ovarian cancer. Nevertheless there is a continuous need for more potent compounds having the broadest possible spectrum of activity on different cancer types.

The present invention provides taxane derivatives modified at 6 and 7 positions of the taxane skeleton (taxol numbering).

More especially, the invention provides taxane derivatives of formula I:

wherein: R3 represents hydrogen atom, hydroxy group or a group of formula -OCOR', -OR', -OSO2R', -OCONR'R'', -OCONHR' or -OCOOR' wherein R' and R'' each independently represents Cl-C6 alkyl, C2 C6 alkenyl, C3-C6 cycloalkyl, C2-C6 alkynyl or a phenyl group optionally substituted with one, two or three, same or different substituents selected from a halogen atom, C1-C6 alkyl, C1-C6 alkoxy and CF3 groups; R4 is -COR''' or -COOR''' wherein R''' represents C1-C6 alkyl, C2-C6 alkenyl, C3-C6 cycloalkyl, C2-C6 alkynyl or a phenyl group optionally substituted with one, two or three, same or different substituents selected from a halogen atom, Cl-C6 alkyl, Cl-C6 alkoxy, and CF3 groups; and (i) R1 together with R2 represents an oxygen atom or a group of the formula )N-Z or yCH-Z or (ii) Rl represents a hydroxy group and R2 represents a hydrogen atom, azido group or a group of formula NRsR6 or (iii) Rl represents an azido group or a group of the formula NR5R6 and R2 represents a hydroxy group, wherein Z is a hydrogen atom, carboxy or a C1-C6 alkoxycarbonyl group and R, and R6 each independently represents a hydrogen atom or a Cl-C6 alkyl, Cl-C8 alkanoyl or C7-Cll aroyl group; and pharmaceutically acceptable salts thereof.

The wavy lines indicate that the substituents may be in the a or ss configuration or both, i.e. a mixture of stereoisomers is present.

A C1-C6 alkyl group is a straight chain or branched alkyl group, preferably a Cl-C4 alkyl group such as methyl, ethyl, npropyl, isopropyl, n-butyl, isobutyl, sec-butyl or tert-butyl.

A C2-C6 alkenyl group is a straight chain or branched alkenyl group, preferably a C2-Cs alkenyl group such as vinyl, allyl, crotyl, 2-methyl-1-propenyl, 1-methyl-1-propenyl, butenyl or pentenyl.

The C3-C6 cycloalkyl group is a saturated carbocyclic group of from 3 to 6 carbon atoms, such as cyclopropyl, cyclobutyl, cyclopentyl or cyclohexyl.

The term halogen encompasses fluorine, chlorine, bromine or iodine.

A C2-C6 alkynyl group is a straight chain or branched alkynyl group, preferably a C2-C4 alkynyl group such as ethynyl, propargyl, 1-propynyl, 1-butynyl or 2-butynyl.

A C7-Cll aroyl group is intended to include benzoyl or naphthoyl residues.

A C1-Cs alkanoyl group is a straight chain or branched alkanoyl group, preferably a C1-C5 alkanoyl group such as acetyl, propanyl, methanoyl or pivaloyl.

A Cl-C6 alkoxy group is a straight chain or branched alkoxy group, preferably a C1-C4 alkoxy group such as methoxy, ethoxy, propoxy or tert-butyoxy.

A Cl-C6 alkoxycarbonyl group is a straight chain or branched alkoxycarbonyl group, preferably a C1-C4 alkoxylcarbonyl group such as a methoxycarbonyl, ethoxycarbonyl, propoxycarbonyl or tert-butoxy carbonyl group.

Preferred compounds of the invention are the taxane derivatives of the formula I wherein: R3 represents hydrogen atom, hydroxy group or a group of formula -OCOR', -OR', -OSO2R', -OCONR'R'', -OCONHR' or -OCOOR' wherein R' and R'' each independently represents C1-C4 alkyl, C2 C4 alkenyl, C3-C6 cycloalkyl, C2-C4 alkynyl or a phenyl group optionally substituted with one, two or three, same or different substituents selected from a halogen atom, C1-C4 alkyl, C1-C4 alkoxy and CF3 groups;; R4 is -COR''' or -COOR''' wherein R''' represents Cl-C4 alkyl, C2-C4 alkenyl, C3-C6 cycloalkyl, C2-C4 alkynyl or a phenyl group optionally substituted with one, two or three, same or different substituents selected from a halogen atom, C1-C4 alkyl, C1-C4 alkoxy, and CF3 groups; and (i) R1 together with R2 represents an oxygen atom or a group of the formula N-Z; or ,CH-Z or (ii) R1 represents a hydroxy group and R2 represents a hydrogen atom, azido group or a group of formula NR5R6 or (iii) R1 represents an azido group or a group of the formula NR5R6 and R2 represents a hydroxy group; wherein Z is a hydrogen atom, carboxy or a C1-C4 alkoxycarbonyl group and Rs and R6 each independently represents a hydrogen atom or a C1-C4 alkyl, C1-Cs alkanoyl, benzoyl or naphthoyl group; and pharmaceutically acceptable salts thereof.

Preferably R and/or R is methyl. Preferably R"' represents phenyl, tert-butyl, 1-methyl-1-propenyl or n-penyl; more preferably R represents phenyl or tert-butyl. Preferably R4 represents -COPh or -CO2tBu. Preferably R3 represents -CO2CH3 or OH. The pharmaceutically acceptable salt is typically the hydrochloride or the hydrobromide salt.

Further preferred compounds of the invention are 7-deoxy-6,7-epoxy-taxol, 7-deoxy-6,7-epoxy-taxotere, 7-dexoy-6,7-imino-taxol, 7-deoxy-6,7-imino-taxotere, 6-amino-taxol, 6-amino-taxotere, 6-hydroxy,7-deoxy,7-amino-taxol, 6-hydroxy,7-deoxy,7-amino-taxotere, 6-hydroxy,7-deoxy-taxol, 6-hydroxy,7-deoxy-taxotere 7-deoxy-6,7-methylene-taxol, 7-deoxy-6,7-methylene-taxotere, 7-deoxy-6,7-carboxymethylene-taxol and 7-deoxy-6,7-carboxymethylene-taxotere The present invention also provides a process for the preparation of taxane derivatives of the formula I, as above defined. In fact, structures of formula I can be obtained from a properly 2'-O-protected (for example as the acetate or benzylcarbonate) taxane derivative having a double bond linking positions 6 and 7.Accordingly, the present invention provides a process for preparing a taxane derivative of formula I, or a pharmaceutically acceptable salt thereof, the process comprising: (a) (i) carrying out the epoxidation or the cyclopropanation of a corresponding 6,7 unsaturated taxol derivative of the formula II:

wherein R3 and R4 are as defined above and R7 is a hydroxy protecting group, and then opening if desired the resulting 6,7epoxide ring either with an appropriate nucleophile or in a reductive fashion, thus producing a compound of formula IV

wherein:: R1 and R2 together represent an oxygen atom or a group of the formula CH-Z wherein Z is as defined above or Rl represents a hydroxy group and R2 represents a hydrogen atom, azido group or a group of formula NRsR6 wherein R5 and R6 are as defined in claim 1 or R1 represents an azido group or a group of the formula NR5R6 wherein R5 and R6 are as defined above and R2 represents a hydroxy group or (a) (ii) directly transforming a compound of the formula II by an oxyamination reaction into a hydroxy-amino derivative of formula IV wherein one of R1 and R2 is a hydroxy group and the other is a said group of formula NR5R6 wherein Rs and R6 are as defined above;; (b) optionally converting a resultant hydroxy-azido or a hydroxy-amino derivative of formula IV into a corresponding 6,7imino analog; (c) removing the said hydroxy protecting group R7; and (d) optionally salifying the resulting taxane derivative of formula I to form a pharmaceutically acceptable salt thereof.

The 6,7-imino analogs can be obtained either from the hydroxy-azido or from the hydroxy-amino derivatives using literature methods. Finally, the hydroxy protecting group is removed and, if desired, the resulting compound is salified by treatment with the appropriate acid. The hydroxy protecting group which R7 represents may be COCH3, -COCH2Ph, -COCH2CH=CH2, Et3Si-, (i-Pr)3Si-, t-BuMe2Si-, t-BuPh2Si- or another suitable hydroxy protecting group.

The epoxidation of the 6,7 unsaturated taxol derivative of formula II can be performed utilizing a peroxyacid, like metachloraperbenzoic acid (mCPBA), in dichloromethane at room temperature, or using an excess of dimethyldioxirane in acetone at room temperature.

The cyclopropanation can be performed by reacting the 6,7 unsaturated taxol derivative of formula II with dibromomethane/copper (or copper-zinc couple) in an aprotic solvent. Such aprotic solvents are typically benzene or ethyl ether. The reaction takes place at a temperature of from room temperature to the boiling temperature of the solvent.

Cyclopropanation can occur also by reacting the 6,7 unsaturated taxol derivative of formula II with an appropriate diazoderivative, for example diazoethylacetate, diazobenzylacetate, etc., in the presence of a proper metallic catalyst in a said aprotic solvent. The metallic catalyst is typically copper acetylacetonate or palladium dichloride. The reaction takes place at a temperature of from room temperature to the boiling temperature of the solvent.

A hydroxy-azido derivative can be obtained by reacting a resulting 6,7-epoxy taxol derivative with an azide or with HN3 in an aprotic solvent. A preferred solvent for the reaction of a 6,7 epoxy taxol derivative with an azide is dimethylformamide (DMF). Treatment of a hydroxy-azido derivative with, a reagent such as triphenylphosphine produces a corresponding 6,7-imino derivative. An imino derivative can be alternatively prepared from a hydroxy-amino derivative by reaction with a reagent such as triphenylphosphine dibromide. A preferred solvent for this reaction is triethylamine.

A hydroxy-amino derivative can be synthesized by treating a 6,7-epoxy taxol derivative with ammonia under pressure in water at 70-800C or with an appropriate amine in the presence of a salt in an aprotic solvent at room temperature. Preferred salts for this purpose are lithium perchlorate and calcium chloride. A preferred solvent for this reaction is acetonitrile. Alternative routes to a hydroxy-amino derivative can be catalytic hydrogenation of a corresponding hydroxy-azido derivative using, for example, palladium on carbon in a solvent like methanol or ethyl acetate, or oxyamination reaction with a 6,7 unsaturated taxol derivative of formula 2, for instance with sodium ptoluenesulphochloramide trihydrate (TsNClNa. 3H2O) (Chloramine-T trihydrate)/osmium tetroxide.

The removal of the hydroxy protecting group R7 can be carried out under standard conditions such as hydrolysis or hydrogenolysis or utilizing tetrabutylammonium fluoride for the removal of silyl groups. When the protecting group is acetyl, it may be removed by treatment with sodium bicarbonate in MeOH/H2O or with diethylamine in methanol.

The 6,7 unsaturated taxane derivatives of formula II are known or may be prepared by known method, starting from known compounds, as described in EP-A-600517 and in our copending U.K.

Patent Application No. 9409131. Thus, the 6,7 unsaturated taxane derivatives of the formula VI

wherein RA represents OR or R wherein R is Cl-C5 alkyl, C2-Cs alkenyl or C6-Cl0 aryl and RB represents H or Ac (CH3CO) can be obtained by an elimination process from a taxane derivative with a suitable leaving group at the 7-position (like triflate, mesylate, etc.) and with a proper protecting group at the 2'-position (like the acetyl group), such as a taxane derivative of the formula VII

wherein RA and RB are as defined above, RC is a leaving group and RD is a hydroxy protecting group, thereby to form a said taxane derivative of formula VI wherein the 2'-hydroxy group carries a said hydroxy protecting group RD; ; optionally separating the resulting isomers which are in the a and p configuration at the 2'-position; and removing the said hydroxy protecting group RD.

The leaving group RC can therefore be CH3SO2O-, CF3SO2O- or another suitable leaving group. RD may be Ac, -OCOCH2Ph, -OCOCH2CH=CH2, (i-Pr)3Si-, t-BuMe2Si-, t-BuPh2Si- or another suitable hydroxy protecting group. The wavy line denotes that the R0 group linked at the 7-position of the taxane structure may be in the a configuration; the p configuration; or both configurations, i.e. a and p.

The elimination reaction is typically achieved by reacting a compound of formula VII with a base. The elimination reaction may thus be performed in the presence of a base such as MeSM, MN3, MCN, M2C03, AcOM, etc (wherein M represents an alkali metal such as Na or K) either in a suitable polar aprotic organic solvent like dimethylformamide, dimethylsulfoxide, acetonitrile etc. or under phase transfer catalysis conditions in the presence of a quaternary ammonium salt (for example n-Bu4NHSO4) and in an apolar organic solvent (for example toluene, benzene, methylene chloride, chloroform, etc). The reaction temperature may vary from OoC to 120 C, for example from 0 to 300C.

The removal of the hydroxy protecting group RD can be carried out under standard conditions such as hydrolysis or hydrogenolysis or utilising tetrabutylammonium fluoride for silyl groups. When the protecting group is Ac, it may be removed by treatment with sodium bicarbonate in MeOH : H20 as reaction medium or with diethylamine in methanol. Removal of the hydroxy protecting group RD yields compounds of formula VI. The separation of the isomers which are a and P at the 2'-position may be carried out by analogy with known methods.

The above taxane derivatives of formula VI can be obtained reacting a compound of formula VIII:

wherein RA, RB and RD are as defined above with a compound of formula IX CX3SO2 -Y IX wherein X is H or F and Y is a leaving group. The leaving group Y may be a halogen (e.g. C1) or -OSO2CX3 or another suitable leaving group.

Compounds of formula VII in fact can be generally obtained by reacting compounds of formulae VIII and IX in the presence of a base (for example pyridine, dimethylaminopyridine, diisopropylethylamine, etc) in a suitable organic solvent which can be pyridine itself, CH3CN, CH2Cl2, etc. The reaction temperature may vary from room temperature to 700C. The reaction time may vary from 1 to 12hrs.

Compounds of formula VIII practically are taxane derivatives with a 2'-hydroxy protecting group. Several examples are already known in the literature. For instance the compound of formula VIII where RA is phenyl, RB and RD are both Ac and the 7-OH configuration is p (i.e. 2'-acetyltaxol) is described in Bioch.

Bioph. Res. Comm. 124, 329 (1984). The compound of formula VIII where RA is phenyl, RB is Ac, RD is -OCOCH2Ph and the 7-OH configuration is p is reported in Tetrah. 49, 2805 (1993) and the same compound where the 7-OH configuration is a is reported in Tetrah. Lett. 34, 6845 (1993).

Analogously the compound of formula VIII wherein Rl is phenyl, R2 and R4 are both Ac and the 7-OH configuration is a (i.e.

2'-acetyl-7-epitaxol) may be obtained, starting from 7-epitaxol already known in the literature (see J. Nat. Prod. 49, 665-9 (1986)). Other compounds of formula VIII are known compounds or may be prepared by known methods from known compounds.

The process of the invention for preparing a taxane derivative of formula I or a salt thereof may further comprise preparing the compound of formula II by reacting a compound of formula III

wherein R3, R4 and R7 are as defined above, with a compound of formula X CX3(CH2)nS02-Y X wherein X is H or F, n is O or 1 and Y is a leaving group, in the presence of a base.

Preferably the compound of formula X is 2,2,2-trifluoroethanesulfonylchloride. The leaving group Y may be a halogen (e.g Cl) or -OSO2CX3 wherein X is as defined above, or another suitable leaving group.

The base is preferably an organic base such as triethylamine, diisopropylethylamine, pyridine or 4- dimethylaminopyridine (DMAP). More preferably, the base is 4-dimethylaminopyridine (DMAP).

The present invention further provides a process for preparing a taxane derivative of the formula V

wherein R3 and R4 are as defined above which processs comprises: (a) treating a compound of the formula III as defined in above with 2,2,2 trifluoroethanesulphonylchloride in the presence of a base, and (b) removing the R, hydroxy protecting group from the resulting 6,7-unsaturated taxane derivative The reaction of the compound of formula III is preferably carried out in a solvent such as pyridine at a temperature of from 40 to 1000C, preferably at 800C, using as a base 4dimethylamino-pyridine (DMAP).

The compounds of the formula III are known compounds or may be prepared starting from known compounds by means of known procedures.

BIOLOGICAL ACTIVITY The cytotoxic activity of the compounds has been evaluated on B16-F10 murine melanoma cell line which was responsive to taxol.

The mode of action of the compound was also tested on the tubulin assembly-disassembly assay in comparison with taxol.

In vitro drua sensitivitv assay.

Exponentially growing B16-F10 murine melanoma cells were seeded (2x104/ml) in RPMI 1640 medium supplemented with 10% heatinactivated fetal calf serum and 2mM glutamine in 24-well plates (Costar). Scaled concentrations of tested compounds were added immediately after seeding.

The inhibition of cell growth was evaluated by counting cells with a Coulter counter after 24hrs incubation. For each tested compound concentration triplicate cultures were used. The antiproliferative activity of the tested compounds was calculated from dose-response curves and expressed as IC50 (dose causing 50% inhibition cell growth in treated cultures relative to untreated controls). The results are shown in Table 1.

Microtubule assembly-disassomhls assay.

Calf brain tubulin was prepared by two cycles of assemblydisassembly (Shelanski M.L., Gaskin F. and Cantor C.R., Proc.Natl.Acad.Sci. U.S.A. 70, 765-768, 1973) and stored in liquid nitrogen in MAB (0.1 M MES, 2.5 mM EGTA, 0.5 mM MgS04 0.1 mM EDTA, 0.1 mM DTT pH 6.4). All the experiments were carried out on protein stored for less than 4 weeks. Before each experiment, tubulin was kept 30 min at 40C. Assembly was monitored by the method of Gaskinet al. (Gaskin F., Cantor C.R. and Shelanski M.L., J.Molec.Biol. 89, 737-758, 1974).

The cuvette (1 cm path) containing tubulin (lmg/ml) and 1 mM GTP was shifted to 370C and continuous turbidity measurements were made at 340 nm on a Perkin-Elmer 557 double wavelength, double beam spectrophotometer equipped with an automatic recorder and a thermostatically regulated sample chamber. After 30 minutes, 4 mM CaCl2 was added and depolymerisation was measured for 10 minutes as decreased turbidity. At regular intervals of 15 minutes scaled doses of the tested compounds were added and variations in the turbidity were monitored. Data are expressed as percentage of repolymerization induced by the tested compounds.

The results are shown in Table I.

Table I Example Tubulin assembly(%) Cytotoxicity 0.5nM 5nM IC50 (nM) B16F10 3 Paclitaxel 39+2 93+3 36+10 The taxane derivatives of formula I are thus antitumor agents. A human or animal suffering from a tumor may thus be treated by a method which comprises the administration thereto of an effective amount of a taxane derivative of formula I according to the invention. The condition of the human or animal may thereby be improved.

Examples of tumors that can be treated are sarcomas, carcinomas, lymphomas, neuroblastomas, melanomas, myelomas, Wilms tumor, leukemias and adenocarcinomas. Taxane derivatives of formula I can be used to treat ovarian cancer, platinum-resistant ovarian cancer, metastatic breast cancer, non-small cell lung cancer, and head and neck cancer.

The invention also provides a pharmaceutical composition which comprises, as active ingredient, a compound of formula I according to the invention and a pharmaceutically acceptable carrier or diluent. The composition of the invention is usually prepared following conventional methods and is administered in a pharmaceutically suitable form.

Administration can be made by any of the accepted ways for administration of antitumor agents such as intravenous, intramuscular or subcutaneous injection or topical application.

For systemic injection the active compound may be, e.g., dissolved in a vehicle consisting of a mixture of polyoxyethylated castor oil (Chremophor EL) 50% and ethanol 50% and then diluted with glucose 5% solution at the desired concentration, or in other pharmaceutically suitable carriers.

The amount of the active compound administered depends on the treated subject, age, weight, sex etc., and the severity of the affliction. The method of administration depends on the judgement of the prescribing physician. A suitable dosage for an average 70 kg person may range from about 0.01g to about ig per day.

The following Examples illustrate the invention but they are not intended to limit it thereto.

Reference Example 1 2' -Acetvl-7-eitaxol 539mg (0.631 mmol) of 7-epitaxol in pyridine (4mL) under nitrogen were treated with acetic anhydride (295yL, 3.13 mmol) at OOC.

The reaction mixture was stirred at OOC for lhr, then poured into ice-water and extracted twice with ethyl acetate. The organic phase was washed once with 1N HCl, once with brine and then dried over sodium sulphate, filtered and evaporated under vacuum, yielding 539mg (95k) of the title compound as a white crystalline solid.

H NMR (CDCl3, 400 MHz) 1.14 (s, 3H, CH3 -16) 1.18 (s, 3H, CH3-17) 1.67 (s, 3H, CH3-19) 1.77 (s, 1H, OH-l) 1.90 (d, J= 1.2 Hz, 3H, CH3-18) 2.14, 2.19 (two singlets, 6H, CH3CO-2'+ CH3CO-10) 2.0 - 2.4 (m, 4H, CH2-14 + CH2-6) 2.54 (s, 3H, CH3CO-4) 3.71 (ddd, J = 11.7 Hz, J = 5.0 Hz, J = 2.0 Hz, 1H, H-7) 3.93 (d, J = 7.5 Hz, 1H, H-3) 4.39 (s, 2H, CH2-20) 4.70 (d, J = 11.7 Hz, 1H, OH-7) 4.94 (dd, J = 3.5 Hz, J = 9.1 Hz, 1H, H-5) 5.56 (d, J = 3.2 Hz, 1H, H-2') 5.76 (d, J = 7.5 Hz, 1H, H-2) 5.98 (dd, J = 3.2 Hz, J = 9.4 Hz, 1H, H-3') 6.22 (m, 1H, H-13) 6.82 (s, 1H, H-10) 6.90 (d, J = 9.4 Hz, 1H, NH) 7.3 - 8.2 (m, 15H, 3 Ph) Reference Example 2 2'-Acetyl-7-eDi-methanesulphonvltaxol To a solution of 404mg (0.451 mmol) of 2'-acetyl-7-epitaxol in pyridine (6mL) under nitrogen were added dimethylaminopyridine (55mg, 0.45 mmol) and, dropwise at OOC, methanesulphonylchloride (882yL , 11.39 mmol). The reaction mixture was allowed to warm to room temperature and then heated at 500C for 18hrs. The reaction mixture was poured into ice-water, extracted with ethyl acetate, the organic phase washed once with 1N HCl, with brine, dried over sodium sulphate, filtered and evaporated under vacuum.

The crude mixture was purified by flash chromatography over silica gel (eluant : n-hexane/ethyl acetate = 1/1) yielding 298mg (68%) of the title compound as a white solid. 42.5mg (11%) of the starting material were recovered.

1H NMR (CDCl3, 400 MHz) 1.16 (s, 3H, CH3-16) 1.20 (s, 3H, CH3-17) 1.77 (s, 3H, CH3-l9) 2.01 (d, J= 1.2 Hz, 3H, CH3-18) 2.15, 2.19 (two singlets, 6H, CH3CO-2 + CH3CO-10) 2.1 - 2.3 (m, 2H, CH-14 + CH-6) 2.49 (s, 3H, CH3CO-4) 2.51 (dd, J = 15.2 Hz, J = 9.4 Hz, 1H, CH-14) 3.08 (ddd, J = 16.4 Hz, J = 9.1 Hz, J = 2.9 Hz, 1H, CH-6) 3.25 (s, 3H, CH3SO2-) 4.09 (d, J = 7.3 Hz, 1H, H-3) 4.33, 4.54 (two doublets, J = 8.5 Hz, 2H, CH2-2 0) 4.70 (dd, J = 2.9 Hz, J = 2.9 Hz, 1H, H-7) 5.04 (dd, J = 5.6 Hz, J = 9.1 Hz, 1H, H-5) 5.54 (d, J = 2.9 Hz, 1H, H-2') 5.76 (d, J = 7.3 Hz, 1H, H-2) 6.01 (dd, J = 2.9 Hz, J = 9.4 Hz, 1H, H-3') 6.25 (m, 1H, H-13) 6.49 (5, 1H, H-10) 6.88 (d, J = 9.4 Hz, 1H, NH) 7.3 - 8.2 (m, 15H, 3 Ph) Reference ExamDle 3 2' -Acetvl-7-deoxv-taxol-6 -ene To a solution of 2'-acetyl-7-epimethanesulphonyltaxol (391mg, 0.127 mmol) under nitrogen in N,N-dimethylformamide (8mL) was added sodium azide (330mg, 5.075 mmol). The reaction mixture was stirred at about 900C for Shrs, then treated with water and ethyl acetate. The organic phase was washed twice with water, once with brine, dried over sodium sulphate, filtered and evaporated under vacuum. The crude mixture was purified by chromatography over silica gel (eluant:n-hexane/ethyl acetate = 1/1) yielding 128mg (36%) of the title compound.

111 NMR (CDCl3, 400 MHz) 1.14 (s, 3H, CH3-16) 1.24 (s, 3H, CH3-17) 1.85 (d, J= 1.2 Hz, 3H, CH3-18) 1.87 (s, 3H, CH3-19) 2.14, 2.22 (two singlets, 6H, CH3CO-2' + CH3CO-10) 2.1 - 2.5 (m, 2H, CH2-14) 2.44 (s, 3H, CH3CO-4) 4.02 (d, J = 6.2 Hz, 1H, H-3) 4.32, 4.44 (two doublets, J = 8.5 Hz, 2H, CH2-20) 5.12 (d, J = 5.6 Hz, 1H, H-5) 5.51 (d, J = 3.1 Hz, 1H, H-2') 5.86 (m, 2H, H-2 + H-7) 5.95 (dd, J = 3.1 Hz, J = 9.1 Hz, 1H, H-3') 6.07 (dd, J = 5.6 Hz, J = 10.0 Hz, 1H, H-6) 6.23 (m, 2H, H-13 + H-10) 6.89 (d, J = 9.1 Hz, 1H, NH) 7.3 - 8.2 (m, 15H, 3 Ph) Reference Example 4 7 -Deoxv-taxol -6 -ene To a suspension of 2'-acetyl-7-deoxy-taxol-6-ene (21mg, 0.024 mmol) in MeOH :H2O = 9 : 1 (5mL) was added sodium bicarbonate (5mg, 0.059 mmol). The reaction mixture was stirred for 3hrs at room temperature and then kept for 24hrs at OOC. The reaction mixture was diluted with water, extracted with ethyl acetate, the organic phase washed with water, brine and dried over sodium sulphate. The crude material was purified by chromatography over silica gel (eluant : n-hexane/ethyl acetate = 1/2) yielding 9.5mg (47%) of the title compound.

Rf , 0.29 (n-hexane/ethyl acetate = 1/1) FAB-MS:m/z 834, [M-H] 111 NMR (CDCl31 400) 1.15 (s, 3H, CH3-16) 1.24 (s, 3H, CH3-17) 1.69 (d, J= 1.5 Hz, 3H, CH3-18) 1.87 (s, 3H, CH3-19) 2.23 (s, 3H, CH3CO-10) 2.2 - 2.5 (m, 2H, CH2-14) 2.39 (s, 3H, CH3CO-4) 3.56 (d, J = 4.4 Hz, 1H, OH-2') 4.00 (d, J = 6.5 Hz, 1H, H-3) 4.33 ,4.43 (two doublets, J = 8.5 Hz, 2H,CH2-20) 4.78 (dd, J = 4.4 Hz, J = 2.5 Hz, 1H, H-2') 5.10 (d, J = 5.6 Hz, 1H, H-5) 5.80 (dd, J = 2.5 Hz, J = 8.8 Hz, 1H, H-3') 5.84 (d, J=6.5 Hz, 1H, H-2) 5.87 (d, J=10.0 Hz, 1H, H-7) 6.06 (dd, J=10.0 Hz, J=5.6 Hz, 1H, H-6) 6.20 (m, 2H, H-10+H-13) 7.02 (d, J=8.8 Hz, 1H, NH) 7.2-8.2 (m, 15H, 3 Ph) Example 1 a6,7 taxol To a stirred solution of 2'-acetyl, 7-epi taxol (lg, l.lmmoles) and p-N,N-dimethylaminopyridine (138mg), in pyridine (15ml) at OOC, 2,2,2-trifluoroethanesulfonyl chloride (0.62m1,5.6mmoles) was added and the solution was heated to 800C. After 2hrs at 800C the reaction was over. The reaction mixture was poured into ice, ethyl acetate was added and the organic layer was washed with water(250mlx3) and then with brine. After drying over sodium sulfate and concentration, the crude material was purified by flash chromatography on silica gel (eluant n-hexane/ethyl acetate 1:1). Obtained 520mg (0.582mmoles, 53% yield) of pure product.

Removal of the 2'-acetyl protecting group was achieved as usual with diethylamine in dichloromethane-methanol (1:10).

Example 2 2' -acetyl, 7-deoxy-6,7-epoxy-taxol To a solution of 2'-acetyl, b6,7 taxol (92mg, 0.105mmoles), in acetone (5ml) a solution of dimethyldioxirane in acetone (1.5ml, theoretical concentration 0.08M) was added under stirring and nitrogen, at room temperature. After 2hrs additional 5ml of dimethyldioxirane in acetone was added and the solution was let overnight at room temperature. The reaction mixture was then concentrated under vacuum and the crude product purified by flash chromatography, eluting with a mixture of n-hexane/ethyl acetate 1:1. Obtained 70mg (0.078mmoles, 75% yield) of pure product.

M.p. OC.

TLC (n-hexane/EtOAc 1:1), Rf=0.55 1H NMR (CDC13, 400MHz) 1.24 (s,3H,CH3-16), 1.60 (s,3H,CH3-17), 1.76 (s,lH,OH-1), 1.88 (s,3H,CH3-19), 1.99 (d,J=1.2Hz,3H,CH3-18), 2.16,2.22 (two singlets,6H,CH3CO-2'+CH3CO-10), 2.20(m,1H,14a), 2.43 (s,3H,CH3CO-4), 2.58 (dd,J=14.9Hz,J=8.8Hz,1H,14b), 3.05 (d,J=3.8Hz,lH,H-7), 3.27 (dd,J=3.8Hz,J=2.9Hz,lH,H-6), 3.97 (d, J=6.5Hz,lH,H-3), 4.25,4.61 (two doublets,J=8.2Hz,2H, CH2-20), 5.47 (d,J=2.9Hz,lH,H-5), 5.67 (d,J=2.9Hz,lH,H-2'), 5.76 (d,J=6.5Hz,lH,H-2), 5.97 (dd,J=2.9Hz,J=9.4Hz,1H,H-3'), 6.24(m,1H,H-13), 6.47 (s,lH,H-10), 6.90 (d,J=9.4Hz,lH,NH-4'), 7.3-8.1 (m,15H,three phenyls).

Example 3 7-deoxy-6,7-epoxy-taxol A mixture of 2'-acetyl, 6,7-epoxy-taxol (16mg, 0.018mmoles), methanol/methylene chloride 10:1 (1.5ml) and diethylamine in methanol (0.7ml of 1% solution) was stirred at room temperature for 2hrs, then concentrated under vacuum and dissolved in ethyl acetate. The reaction mixture was purified by flash chromatography, eluting with dichloromethane/ethyl acetate 7:1.

Obtained 12mg (0.014mmoles, 78% yield) of pure product.

M.p. OC.

TLC (n-hexane/EtOAc 1:1), Rf=0.45 1H NMR (CDCl3, 400MHz): 1.15 (s,3H,CH3-16), 1.22 (s,3H,CH3-17), 1.78 (s,lH,OH-1), 1.79 (d,J=1.2Hz,3H,CH3-18), 1.88 (s,3H,CH3-19), 2.22 (s,3H,CH3CO-10), 2.38 (s,3H,CH3CO-4), 2.2-2.5 (m,2H,CH2-14), 3.02 (d,J=4.1Hz,lH,H-7), 3.26 (dd,J=4.1,J=2.9Hz,lH,H-6), 3.74 (d,J=4.4Hz,lH,OH-2'), 4.02 (d, J=6.5Hz,lH,H-3), 4.27,4.49 (two doublets,J=8.2Hz,2H,CH2-20), 4.80 (dd,J=2.4Hz,J=4.4Hz,1H,H-2'), 5.36 (d,J=2.9Hz,lH,H-5), 5.74 (d,J=6.5Hz,lH,H-2), 5.83 (dd,J=2.4Hz,J=9.1Hz,1H,H-3'), 6.18(m,1H,H-13), 6.43 (s,lH,H-10), 7.13 (d,J=9.1Hz,1H,NH-4'), 7.3-8.1 (m,15H,three phenyls).

Claims (11)

1. A taxane derivative of formula I

wherein: R3 represents hydrogen atom, hydroxy group or a group of formula -OCOR', -OR', -OSO2R', -OCONR'R'', -OCONHR' or -OCOOR' wherein R' and R'' each independently represents Cl-C6 alkyl, C2 C6 alkenyl, C3-C6 cycloalkyl, C2-C6 alkynyl or a phenyl group optionally substituted with one, two or three, same or different substituents selected from a halogen atom, Cl-C6 alkyl, C1-C6 alkoxy and CF3 groups;; R4 is -COR''' or -COOR''' wherein R''' represents C1-C6 alkyl, C2-C6 alkenyl, C3 -C6 cycloalkyl, C2-C6 alkynyl or a phenyl group optionally substituted with one, two or three, same or different substituents selected from a halogen atom, Cl-C6 alkyl, C1-C6 alkoxy, and CF3 groups; and (i) Rl together with R2 represents an oxygen atom or a group of the formula > N-Z orXH-Z or (ii) Rl represents a hydroxy group and R2 represents a hydrogen atom, azido group or a group of formula NR5R6 or (iii) Rl represents an azido group or a group of the formula NRsR6 and R2 represents a hydroxy group, wherein Z is a hydrogen atom, carboxy or a Cl-C6 alkoxycarbonyl group and R5 and R6 each independently represents a hydrogen atom or a Cl-C6 alkyl, C1-C8 alkanoyl or C,-Cll aroyl group; and pharmaceutically acceptable salts thereof.

2. A compound according to claim 1 wherein: R3 represents hydrogen atom, hydroxy group or a group of formula -OCOR', -OR', -OSO2R', -OCONR'R'', -OCONHR' or -OCOOR' wherein R' and R'' each independently represents Cl-C4 alkyl, C2 C4 alkenyl, C3-C6 cycloalkyl, C2-C4 alkynyl or a phenyl group optionally substituted with one, two or three, same or different substituents selected from a halogen atom, Cl-C4 alkyl, Cl-C4 alkoxy and CF3 groups;; R4 is -COR''' or -COOR''' wherein R''' represents Cl-C4 alkyl, C2-C4 alkenyl, C3-C6 cycloalkyl, C2-C4 alkynyl or a phenyl group optionally substituted with one, two or three, same or different substituents selected from a halogen atom, Cl-C4 alkyl, Cl-C4 alkoxy, and CF3 groups; and (i) Rl together with R2 represents an oxygen atom or a group of the formula > -Z; orXH-Z or (ii) Rl represents a hydroxy group and R2 represents a hydrogen atom, azido group or a group of formula NR5R6 or (iii) Rl represents an azido group or a group of the formula NRsR6 and R2 represents a hydroxy group; wherein Z is a hydrogen atom, carboxy or a Cl-C4 alkoxycarbonyl group and Rs and R6 each independently represents a hydrogen atom or a C1-C4 alkyl, C1-Cs alkanoyl, benzoyl or naphthoyl group.

3. A compound according to claim 1 or 2, wherein R''' represents phenyl, tert-butyl, l-methyl-l-propenyl or n-pentyl.

4. A compound according to anyone of the preceeding claims, which is 7-deoxy-6,7-epoxy-taxol, 7-deoxy-6,7-epoxy-taxotere, 7-deoxy-6,7-imino-taxol, 7-deoxy-6,7-imino-taxotere, 6-amino-taxol, 6-amino-taxotere, 6-hydroxy,7-deoxy,7-amino-taxol, 6-hydroxy,7-deoxy,7-amino-taxotere, 6-hydroxy,7-deoxy-taxol, 6-hydroxy,7-deoxy-taxotere 7-deoxy-6,7-methylene-taxol, 7-deoxy-6,7-methylene-taxotere, 7-deoxy-6,7-carboxymethylene-taxol or 7-deoxy-6,7-carboxymethylene-taxotere

5.A process for preparing a taxane derivative of formula I as defined in claim 1 or a pharmaceutically acceptable salt thereof, the process comprising: (a) (i) carrying out the epoxidation or the cyclopropanation of a corresponding 6,7 unsaturated taxol derivative of the formula II:

wherein R3 and R4 are as defined in claim 1 and R, is a hydroxy protecting group, and then opening if desired the resulting 6,7epoxide ring either with an appropriate nucleophile or in a reductive fashion, thus producing a compound of formula IV wherein::

R1 and R2 together represent an oxygen atom or a group of the formula CH-Z wherein Z is as defined in claim 1 or R1 represents a hydroxy group and R2 represents a hydrogen atom, azido group or a group of formula NRSRE wherein R5 and R6 are as defined in claim 1 or R1 represents an azido group or a group of the formula NR5R6 wherein Rs and R6 are as defined above and R2 represents a hydroxy group or (a) (ii) directly transforming a compound of the formula II by an oxyamination reaction into a hydroxy-amino derivative of formula IV wherein one of R1 and R2 is a hydroxy group and the other is a said group of formula NR5R6 wherein Rs and R6 are as defined above;; (b) optionally converting a resultant hydroxy-azido or a hydroxy-amino derivative of formula IV into a corresponding 6,7imino analog; (c) removing the said hydroxy protecting group R7; and (d) optionally salifying the resulting taxane derivative of formula I to form a pharmaceutically acceptable salt thereof.

6. A process according to claim 5, further comprising preparing the compound of formula II by reacting a compound of formula III

wherein R3, R4 and R7 are as defined in claim 5, with a compound of formula X: CX3(CH2)nSO2~Y X wherein X is H or F, n is O or 1 and Y is a leaving group, in the presence of a base.

7. A process according to claim 6 in which the compound of formula X is 2,2,2-trifluro-ethanesulfonyl-chloride.

8. A process for preparing a taxane derivative of the formula V

wherein R3 and R4 are as defined in claim 1, which processs comprises: (a) treating a compound of the formula III as defined in claim 6 with 2,2,2 trifluoroethanesulphonylchloride in the presence of a base, and (b) removing the R, hydroxy protecting group from the resulting 6,7-unsaturated taxane derivative

9. A pharmaceutical composition which comprises, as active ingredient, a compound of the formula I as defined in claim 1 or a pharmaceutically acceptable salt thereof and 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 in a method of treatment of the human or animal body by therapy.

11. A compound as claimed in claim 1 for use as an antitumor agent.