WO1996014309A1

WO1996014309A1 - Taxane derivatives

Info

Publication number: WO1996014309A1
Application number: PCT/EP1995/004303
Authority: WO
Inventors: Maria Menichincheri; Walter Ceccarelli; Marina Ciomei; Domenico Fusar Bassini; Nicola Mongelli; Ermes Vanotti
Original assignee: Pharmacia & Upjohn S.P.A
Priority date: 1994-11-04
Filing date: 1995-11-02
Publication date: 1996-05-17
Also published as: EP0738266A1; JPH09507864A

Abstract

Taxane derivatives modified at 7-position of the taxane derivative skeleton (taxol numbering) of formula (I) wherein R1 is N3, CN, 1H-tetrazol-5-yl, or -NR7R8 and R2, R3, R4, R7 and R8 are organic residues, are endowed 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 10-deacetyl baccatin III, extracted from the needles of Taxus baccata L. (see ani 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 platinum- resistant 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 the 7-position of the taxane skeleton (taxol numbering) . More especially, the invention provides taxane derivatives of formula

I:

wherein R, represents azido, cyano, lH-tetrazol-5-yl or a residue of formula NR₇R_g wherein R₇ and R₈ independently represent hydrogen or a C,-C₆ alkyl, C,-C₈ alkanoyl or C₇-C_n aroyl group,*

R₂ represents a hydrogen atom, hydroxy group or a group of formula -OCOR' , -OR', -OS0₂R' , -OCONR'R", -OCONHR, or -OCOOR' wherein R' and R' ' each independently represent C]-C₆ alkyl, preferably methyl, C₂-C₆ alkenyl, C₃-C₆ cycloalkyl, C₂-C₆ alkynyl or a phenyl group, optionally substituted with one, two or three substituents which may be the same or different and which are selected from a halogen atom, C,-C₆ alkyl, C_} -C₆ alkoxy and -CF₃ groups,*

R₃ is -COR' ' ' or -COOR' ' ' wherein R' ' ' represents C,-C₆ alkyl, C₂-C₆ alkenyl, C₃-C₆ cycloalkyl, C₂-C₆ alkynyl or a phenyl group, optionally substituted with one, two or three substituents which may be the same or different and which are selected from a halogen atom, C]-C₆ alkyl, C,-C₆ alkoxy and -CF₃ groups,- and

R₄ is C]-C₆ alkyl, C₂-C₆ alkenyl, C₃-C₆ cycloalkyl or a radical of the formula -W-R_x in which W is a bond, C₂-C₆ alkenediyl or -{CH₂)_n- where n is from 1 to 6 such as from 2 to 4 and R_x is naphthyl, phenyl or heteroaryl optionally substituted with one, two or three substituents which may be the same or different and which are selected from C,-C₆ alkyl, Cj-C₆ alkoxy, halogen and -CF₃ groups, or a pharmaceutically acceptable salt thereof. Preferably, R' ' ' represents phenyl, tert-butyl, l-methyl- l- propenyl or n-pentyl,* more preferably phenyl. Preferably R₄ is phenyl.

The wavy lines indicate that the hydroxy group at the 2' -position and the substituent at the 7-position may be in the or β configuration, or both, i.e. a mixture of stereoisomers is present.

A C_!*-C₆ alkyl group is a straight or branched alkyl group, preferably a C,-C₄ alkyl group such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl or tert-butyl. A C₂-C₆ alkenyl group is a straight or branched alkenyl group, preferably a C₂-C₅ alkenyl group e.g. vinyl, allyl, crotyl, 2-methyl-1- propenyl, 1-methyl-1-propenyl, butenyl or pentenyl. A C₃-C₆ cycloalkyl group is a saturated carbocyclic group of 3 to 6 carbon atoms, such as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, preferably cyclohexyl.

A halogen is preferably fluorine, chlorine, bromine or iodine. A heteroaryl group is preferably a 3- to 6-membered, saturated or unsaturated heterocyclyl ring which contains at least one, for example 1, 2 or 3, heteroatoms selected from 0, S and N and which is optionally fused to a second 5- or 6-membered, saturated or unsaturated heterocyclyl group containing one or more, for example 1, 2 or 3, heteroatoms or to a cycloalkyl group or to an aryl group. The 3- to 6- membered heterocyclyl ring may be a 3-, 4-, 5- or 6- membered such ring. A cycloalkyl group is generally a said C₃-C₆ cycloalkyl group. An aryl group is generally phenyl (Ph) or naphthyl. Examples of heterocyclyl groups are pyrrolyl, pyrazolyl, imidazolyl, triazolyl, tetrazolyl, oxazolyl, isoxazolyl, thiazolyl, isothiazolyl, thiadiazolyl,thienyl, furyl, aziridinyl, oxiranyl, azetidinyl, pyridinyl, pyrazinyl, pyrimidinyl, pyranyl, pyridazinyl, benzothienyl, benzothiazolyl, benzoxazolyl, isobenzofuranyl, benzofuranyl, chromenyl, indolyl, indolizinyl, isoindolyl, cinnolinyl, indazolyl and purinyl. A C₂-C₆ alkenediyl chain can be a straight or branched alkenediyl preferably a C₂-C₄ alkenediyl chain such as -CH=CH-, -CH=CH-CH₂- or -CH(CH₃) -CH=CH- . A C₂-C₆ alkynyl group can be a straight or branched alkynyl group preferably a C₂-C₄ alkynyl group such as ethynyl, propargyl, 1-propynyl, 1-butynyl or 2- butynyl. A C₇-C,, aroyl group is intended to include benzoyl or naphthoyl residues.

A C,-C₆ alkoxy group can be a straight chain or branched alkoxy1 group, preferably a C,-C₄ alkoxy group such as methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy or tert-butoxy. A C,-C₈ alkanoyl group can be a straight chain or branched alkanoyl group, preferably a C,-C₅ alkanoyl group such as methanoyl (Ac) , ethanoyl, n-propanoyl, isopropanoyl, n-butanoyl, tert-butanoyl or n-pentanoyl. The pharmaceutically acceptable salts include the hydrochloride salt, the hydrobromide salt and the sulphate salt. Preferred compounds of the invention are the taxane derivatives of formula I wherein R, represents azido, cyano, 1H- tetrazol-5-yl or a residue of formula NR₇R₈ wherein R₇ and R₈ independently represent hydrogen or a C]-C₄ alkyl, C,-C₅ alkanoyl, benzoyl or naphthoyl group,* R₂ represents a hydrogen atom, hydroxy group or a group of formula -OCOR' , -OR', -OS0₂R' , -OCONR'R", -OCONHR, or -OCOOR' wherein R' and R' ' each independently represent Cj-C₄ alkyl, C₂-C₅ alkenyl, C₃-C₆ cycloalkyl, C₂-C₄ alkynyl or a phenyl group optionally substituted with one, two or three substituents which may be the same or different and which are selected from a halogen atom, C,-C₆ alkyl, C,-C₄ alkoxy and -CF₃ groups; R₃ is -COR' ' ' or -C00R' ' ' wherein R' ' ' represents C,-C₄ alkyl, preferably methyl, C₂-C₅ alkenyl, C₃-C₆ cycloalkyl, C₂-C₄ alkynyl or a phenyl group optionally substituted with one, two or three substituents which may be the same or different and which are selected from a halogen atom, C,-C₄ alkyl, C,-C₄ alkoxy and - CF₃ groups and

R₄ is C,-C₄ alkyl, C₂-C₅ alkenyl, C₃-C₆ cycloalkyl or a radical of the formula -W-R_x in which is a bond, C₂-C₄ alkenediyl or -

(CH₂)_n- where n is from 2 to 4 and R_x is naphthyl, phenyl or heteroaryl optionally substituted with one, two or three substituents which may be the same or different and which are selected from C,-C₄ alkyl, C_j- , alkoxy, halogen and -CF₃ groups; or a pharmaceutically salt thereof.

Preferably R' and/or R" is methyl in a taxane derivative of formula I. Preferably R' ' ' is phenyl, tert-butyl, 1-methyl-l- propenyl or n-pentyl. Preferred compounds of the invention are: 7-deoxy-7-epi-azido-taxol, 7-deoxy-7-epi-amino-taxol, 7-deoxy-7-cyano-taxol and 7-deoxy-7- (lH-tetrazol-5-yl) -taxol.

The present invention also provides a process for the preparation of taxane derivatives of formula I, as above defined, or a pharmaceutically acceptable salt thereof. In fact, structures of formula I can be obtained by a substitution process from a taxane derivative having a suitable leaving group at the 7-position (like triflate, mesylate, tresylate, etc.) and with an optional hydroxy protecting group at the 2'-position (like the acetyl group) .

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) carrying out a substitution reaction with an azide or cyanide salt or a derivative thereof on a taxane derivative of formula II:

wherein R₂, R₃ and R₄ are as defined above, R'₅ is a hydrogen atom or a hydroxy protecting group R₅ and R₆ is a leaving group, thereby to form a taxane derivative having at the 7-position an azido, cyano or lH-tetrazol-5-yl group,*

(b) optionally reducing the said 7-azido derivative and, if desired, derivatizing the resultant 7-amino taxol to give thereby a taxane derivative of formula II where the leaving group R₆ is replaced by a residue of formula NR₇R₈ where R₇ and R₈ are as defined above,*

(c) optionally reacting the said 7-cyano derivative with an appropriate azide to give the corresponding 7- (lH-tetrazol-5-yl) derivative;

(d) removing, if necessary, the said hydroxy protecting group R_s; and (e) optionally salifying the resulting taxane derivative of the formula I to form a pharamceutically acceptable salt thereof. The leaving group R₆ can for example be CH₃S0₂0-, CF₃S0₂0-, CF₃CH₂S0₂0- or another suitable leaving group. R₅ may be -C0CH₃, -C0CH₂Ph, -COCH₂CH=CH₂, Et₃Si-, (i-Pr)₃Si-, t-BuMe₂Si-, t-BuPh₂Si- or another suitable hydroxy protecting group.

The substitution reaction at the 7-position is typically achieved by reacting a compound of formula II with an azide or cyanide ion. The azide is typically sodium azide. The cyanide is typically potassium cyanide. The reaction may be performed in aprotic dipolar solvents, e.g. dimethylformamide (DMF) , dimethyl sulfoxide (DMSO) and the like, as well as in phase-transfer catalysis conditions in the presence of a quaternary ammonium salt (for example tricaprylylmethylammonium chloride (Aliquat 336)) and in an apolar organic solvent (for example toluene, benzene, dichloromethane, chloroform, etc) . The reaction temperature may vary from 0°C to 120°C.

The reduction of the 7-azido group may be carried out by heterogeneous catalytic hydrogenation (using for example palladium on charcoal) or by means of the Staudinger reaction (triphenyl phosphine in a solvent mixture like tetrahydrofuran (THF) /water) . The amino derivatization may be carried out using literature methods,- for example reductive alkylation or acylation. The reaction of the 7-cyano derivative to give a tetrazolyl derivative can be performed using literature methods, for example with trialkyltin azide in toluene.

The removal of the hydroxy protecting group R₃ can be carried out under standard conditions such as hydrolysis or hydrogenolysis or utilizing tetrabutylammonium fluoride for silyl groups. When the protecting group is acetyl, it may be removed by treatment with sodium bicarbonate in MeOH/H₂0 or with diethylamine in methanol. The separation of the isomers which are a and β configuration at the 2'- and 7-positions may be carried out by analogy with known methods.

Taxane derivatives of formula III wherein R_:, R₂, R₃, R₄ and R₅ are as defined above are novel and within the scope of the present invention.

A process for the preparation of taxane derivatives of formula III comprises:

(a) carrying out a substitution reaction with an azide or cyanide salt or a derivative thereof on a taxane derivative of formula II as defined above, thereby to form a taxane derivative having at the 7-position an azido, cyano or lH-tetrazole-5-yl group,*

(b) optionally reducing the said 7-azido derivative and if desired, derivatizing the resultant 7-amino taxol to give thereby a taxane derivative of formula II where the leaving group R₆ is replaced by a residue of formula NR₇R₈ where R₇ and R₈ are defined as above,*

(c) optionally reacting the said 7-cyano derivative with an appropriate azide to give the corresponding 7- (lH-tetrazol-5-yl) derivative.

The taxane derivatives of formula II are either known compounds (for example the mesylate of formula II, where R₃ is -CO-phenyl, R₄ is phenyl, R₆ is -OS0₂CH₃, R₂ is 0-acetyl and R₅ is acetyl [see J.Na .Prod.51, 298 (1988)]), or may be prepared from known compounds using established methods. For instance compounds of formula II can be used as starting materials where R₃ is -CO-phenyl, R₄ is phenyl, R₆ is hydroxy, R₂ is O-acetyl and R₅ is acetyl [see Bioch.Bioph.Res .Comm.124, 329 (1984) or Journal.Nat. Prod.49, 665-9 (1986) ] , or where R₃ is -CO-phenyl, R₄ is phenyl, R₆ is hydroxy, R₂ is O-acetyl and R₅ is COCH₂Ph [see Tetrahedron 49,2805(1993) or Tetr.Lett. 34,6845 (1993)] or trimethylsilyl . These known starting compounds can be activated, for example, using esyl or tresyl chloride or triflic anhydride, in bases such as pyridine at reflux temperature, and then deprotected to give compounds of the formula II wherein R'₅ is a hydrogen atom. 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 drug sensitivity assay.

Exponentially growing B16-F10 murine melanoma cells were seeded (2xl0⁴/ml) in RPMI 1640 medium supplemented with 10% heat-inactivated 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-disassembly assay. Calf brain tubulin was prepared by two cycles of assembly-disassembly (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 4°C. 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 l mM GTP was shifted to 37°C 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

O . 57M 5γM IC₅₀ (nM) B16F10

2 n.d. n.d 26

3 74 169 33

Paclitaxel 39 93 36

(reference compound)

n.d.=not determined

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 or II 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. The taxane derivatives of formulae I and II 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 or II 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, for example on age, weight, sex etc., and also on 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 O.Olg to about lg per day.

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

7-O-trifluoromethanesulphonyl-2'-O-triethylsilyl-taxol To a solution of 2' -O-triethylsisyl-taxol (4.32 g, 4.46 mmole), in freshly distilled pyridine (75 ml) , cooled at -5°C, trifluoromethanesulphonic anhydride (3.8 ml) was added dropwise. After 1 hour at 0°C, the reaction mixture was kept at room temperature for 3 hours.

The reaction mixture was poured into cold 0.1 N HCl and extracted with ethyl acetate. The organic layer was washed with NaCl (saturated solution) , water and dried over Na₂S0₄. After concentration, the product was isolated as a whitish solid (4.7 g, 96% yield) . PREPARATION B

7-O-trifluoromethanesulphonyl-taxol. A solution of 7-0-trifluoromethanesulphonyl-2' -O-triethylsilyl- taxol (4.7 g, 4.27 mmole) in tetrahydrofuran (100 ml) and IN HCl

(7.7 ml) was stirred at room temperature for 30' . The reaction mixture was poured into water and extracted with ethyl acetate.

«

The organic layer was washed with NaCl (saturated solution) , water, dried over Na₂S0₄ and concentrated to yield the title product as a whitish solid in quantitative yield. PREPARATION C 7-0-trifluoromethanesulphonyl-2' -O-acetyl-taxol

To a solution of 2' -O-acetyl taxol (4.3 g, 4.8 mmoles) in pyridine (40 ml) at 0°C, trifluoromethanesulphonic anhydride (4 ml, 23.8 mmole) was added dropwise. The reaction mixture was warmed to room temperature and stirred for 1 hour. The reaction mixture was washed (x3) with IN HCl, then with water and NaCl (saturated solution) , dried over Na₂S0₄ and concentrated. The desired product (4.46 g) was obtained as a whitish solid.

- 15 - Example 1 2 ' -Acetyl, 7 -deoxy, 7 -epi-azido taxol

( III , R,=α-N₃, R₂=0Ac , R₃=- CO -phenyl , R₄=phenyl , R₅=Ac )

A mixture of 2' -acetyl-7-trifluoromethanesulfonyl taxol (84.5mg, 0.082mmol) , sodium azide (84.5mg, 1.3mmol) , tricaprylylmethylammonium chloride (Aliquat 336) (3 drops) in toluene (6ml) and water (6ml) was heated at 80°C for 4hrs . The reaction mixture was cooled to room temperature, the two layers separated and the aqueous phase extracted twice with toluene. The combined organic layers were washed with brine, dried over sodium sulfate, filtered and concentrated to dryness under vacuum. The crude material was purified by flash chromatography on silica gel (eluant: dichloromethane/ethyl acetate 15:1) , yielding 37mg (0.04mmol, 50% yield) . TLC (CH₂Cl₂/EtOAc 6:1) , R_f=0.34 ^•H NMR (CDC1₃, 400MHz) :

1.13 (s,3H,CH₃-16) , 1.18 (s, 3H, CH₃-17) , 1.76 (s, 3H, CH₃-19) , 1.99 (d,J=1.2Hz,3H,CH₃-18) , 2.15, 2.19 (two singlets, 6H, CH₃CO-2' + CH₃CO-10) , 2.48 (s,3H,CH₃CO-4) , 2.1-2.6 (m,4H, CH₂-6+CH₂-14) , 3.77 (dd,J=2.0Hz,J=5.1Hz,lH,H-7) , 3.91 (d, J=7. OHz, IH,H-3) , 4.36, 4.44 (d,J=8.2Hz,2H,CH₂-20) , 5.08 (dd,J=3.8Hz,J=10. OHz, IH,H-5) , 5.56 (d., J=3.2Hz, lH,H-2' ) , 5.73 (d, J=7. OHz , 1H„ H-2 ) , 6.00 (dd, J=3.2Hz, J=9.4Hz, 1H.H-3' ) , 6.24 (m,lH,H-13) , 6.91 (d,J=9.4Hz,lH,NH-4' ) , 6.92 (s.lH.H-10) , 7.3-8.2 (m, 15H, three phenyls) . Example 2 7 -deoxy, 7-epi-azido taxol

( I , R,=c-:-N₃ , R₂=0Ac , R₃=- CO -phenyl , R₄=phenyl , R₅=H)

A mixture of 2' -acetyl,7-deoxy,7-epi-azido taxol (50mg, 0.054mmoles) , methanol (lml) and diethylamine in methanol (1ml of 1% solution) was stirred at room temperature for 2hrs, then concentrated under vacuum and dissolved in ethyl acetate. The organic solution was washed (x2) with 0.5N hydrochloric acid, with brine, dried over sodium sulfate and concentrated under vacuum. The crude product was purified by flash chromatography, eluting with n-hexane/ethyl acetate 1:1. Obtained 15mg (0.017mmoles, 30% yield) of pure product. TLC (n-hexane/EtOAc 1:1), R_f=0.35 Η NMR (CDCI₃. 400MHz) : 1.13 (s,3H,CH₃-16) , 1.19 (s,3H,CH₃-17) , 1.75 (s,3H,CH₃-19) , 1.85 (d,J=1.2Hz,3H,CH₃-18) , 2.20 (s, 3H,CH₃CO-10) , 2.43 (s,3H,CH₃CO-4) , 2.2-2.6 (m,4H,CH₂-6+CH₂-14) , 3.50 (bs, IH,OH-2' ) , 3.75 (dd,J=2.1Hz,J=5.0Hz,lH,H-7) , 3.93 (d, J=7.OHz, IH,H-3) , 4.34, 4.45 (two doublets,J=8.OHz,2H,CH₂-20) , 4.82 (d,J=2.6Hz, IH,H-2' ) , 5.02 (dd,J=3.8Hz,J=9.4Hz, 1H.H-5), 5.73 (d,J=7.OHz, IH,H-2) , 5.84 (dd,J=2.6Hz, J=9.1Hz,lH,H-3' ) , 6.21 (m,lH,H-13), 6.88 (S,1H,H-10), 7.00 (d,J=9.1Hz,lH,NH-4' ) , 7.3-8.2 (m, 15H,three phenyls) . Example 3

7-Deoxy-7-epi-amino-taxol

7-Deoxy-7-epi-azido-taxol (mg. 30, 0.034 mmole) was dissolved in ethylacetate (2 ml) Catalyst 5% Pd/C (35 mg) was added and the reaction mixture subdued to hydrogen atmosphere (48 psi) at room temperature for

72 hours under shaking.

After the filtration and concentration the crude product

(27 mgj was purified on preparative silica gel TLC, eluating with n-hexane/ethylacetate 1/1.

The title compound (10 mg, 0.012 mmole, 34% yield) was isolated as a white solid.

R.f *-= 0.16 (n-hexane/ethylacetate 1/1)

^■H-NMR (400MHz. CDCl,) 1.15 (S, 3H, 16), 1.18 (s, 3H, 17), 1.70 (s, 3H, 19), 1.76 (s,

IH, OH-1) , 1.79 (d, J=1.5Hz, 3H, 18), 2.1-2.5 (m, 4H, CH₂-14+CH₂-

6), 2.19 (s, 3H, CH₃CO-10), 2.46 (s, 3H, CH₃CO-4), 2.89 (d,

J=2.9Hz, IH, 7), 3.45 (bs, IH, OH-2'), 3.92 (d, J=7.3Hz, 1H,3)

4.32, 4.52 (two doublets, J=8.5Hz, 2H, CH₂-20) , 4.80 (d,J=2.6Hz, IH, 2') , 4.95 (dd, J=5.0 Hz, J=9.5 Hz, 1H,5) , 5.74 (d, J=7.3 Hz,

1H,2), 5.83 (dd, J=2.6 Hz, J=9.1 Hz, 1H,3'), 6.21 (m, IH, 13⁾

7.02 (d, J=91HZ, IH, NH-4') , 7.24 (s, IH, 10) ,

7.3-8.2 (m, 15H, 3 Ph) Example 4

7-deoxy-7-epi-azido taxol

(I, R,=α*-N₃, R₂=0Ac, R₃=-CO-phenyl, R₄=phenyl, R_S=H) A solution of 7-0-trifluoromethanesulphonyl taxol (4.3 g) , sodium azide (4.3 g) and Aliquat 336 (registered mark) (5.18 g) in toluene (360 ml) and water (360 ml) was vigorously stirred at 80°C for 2 hours. The reaction mixture was cooled to room temperature, the organic layer was washed with NaCl (saturated solution) , water, dried over Na₂S0₄ and concentrated. The crude product was purified by flash chromatography on silica gel, eluant CH₂Cl₂/EtOAc 4:1. There were obtained 1.52 g (1.7 mmole, 40% yield) of the title compound, having the same physico- chemical data of that prepared in Example 2.

Claims

A taxane derivative of formula I

wherein:

R] represents azido, cyano, lH-tetrazol-5-yl or a residue of formula NR₇R₈ wherein R₇ and R₈ each independently represent hydrogen or a C,-C₆ alkyl, C,-C₈ alkanoyl or C₇-C_n aroyl group,-

R₂ represents a hydrogen atom, hydroxy group or a group of formula -OCOR' , -OR', -0S0₂R' , -OCONR'R", -0C0NHR' or -0C00R' wherein R' and R" each independently represent C,-C₆ alkyl, C₂-C₅ alkenyl, C₃-C₆ cycloalkyl, C₂-C₆ alkynyl or a phenyl group optionally substituted with one, two or three substituents which may be the same or different and which are selected from a halogen atom, C,-C₆ alkyl, C,-C₆ alkoxy and -CF₃ groups,-

R₃ is -COR' ' ' or -C00R' ' ' wherein R' ' ' represents C,-C₆ alkyl, C₂-C₆ alkenyl, C₃-C₆ cycloalkyl, C₂-C₆ alkynyl or a phenyl group, optionally substituted with one, two or three substituents which may be the same or different and which are selected from a halogen atom, C,-C₆ alkyl, C,-C₆ alkoxy and -CF₃ groups,* and R₄ is C_!-C₆ alkyl, C₂-C₆ alkenyl, C₃-C₆ cycloalkyl or a radical of the formula -W-R_x in which W is a bond, C₂-C₆ alkenediyl or -(CH₂)_n- where n is from 1 to 6 and R_x is naphthyl, phenyl or heteroaryl optionally substituted with one, two or three substituents which may be the same or different and which are selected from C[-C₆ alkyl, C,-C₆ alkoxy, halogen and -CF₃ groups, or a pharmaceutically acceptable salt thereof.

2. A compound according to claim 1 wherein R, represents azido, cyano, lH-tetrazol-5-yl or a residue of formula NR₇R₈ wherein R₇ and R₈ independently represent hydrogen or a C,-C₄ alkyl, C,-C₅ alkanoyl, benzoyl or naphthoyl group;

R₂ represents a hydrogen atom, hydroxy group or a group of formula -OCOR' , -OR', -OS0₂R' , -OCONR'R", -0C0NHR, or -OCOOR' wherein R' and R' ' each independently represent C,-C₄ alkyl, C₂-C₅ alkenyl, C₃-C₆ cycloalkyl, C₂-C₄ alkynyl or a phenyl group optionally substituted with one, two or three substituents which may be the same or different and which are selected from a halogen atom, C,-C₄ alkyl, C,-C₄ alkoxy and -CF₃ groups;

R₃ is -COR''' or -COOR' ' ' wherein R' ' ' represents C_]-C₄ alkyl, C₂-C₅ alkenyl, C₃-C₆ cycloalkyl, C₂-C₄ alkynyl or a phenyl group optionally substituted with one, two or three substituents which may be the same or different and which are selected from a halogen atom, C,-C₄ alkyl, C,-C₄ alkoxy and -CF₃ groups,- and

R₄ is C,-C₄ alkyl, C₂-Cj alkenyl, C₃-C₆ cycloalkyl or a radical of the formula -W-R_x in which W is a bond, C₂-C₄ alkenediyl or -(CH₂)_n- where n is from 2 to 4 and R_x is naphthyl, phenyl or heteroaryl optionally substituted with one, two or three substituents which may be the same or different and which are selected from C,-C₄ alkyl, C,-C₄ alkoxy, halogen and -CF₃ groups, or a pharmaceutically acceptable salt thereof.

3. A compound according to claim 1 or 2 wherein R' and/or R' ' is methyl.

4. A compound according to any one of the preceding claims wherein R' ' ' is phenyl, tert-butyl, 1-methyl-1-propenyl or n- pentyl.

5. A compound according to claim 1 which is selected from 7-deoxy-7-epi-azido-taxol, 7-deoxy-7-epi-amino-taxol, 7-deoxy-7-cyano-taxol, 7-deoxy-7- (lH-tetrazol-5-yl) -taxol.

6. A process for preparing a taxane derivative of formula I as defined in claim 1 or a pharmaceutically acceptable salt thereof, which process comprises:

wherein R₂, R₃ and R₄ are as defined in claim 1, R'₅ is hydrogen or a hydroxy protecting group R₅ and R₆ is a leaving group, thereby to form a taxane derivative having at the 7-position an azido, cyano or lH-tetrazol-5-yl group;

(b) optionally reducing the said 7-azido derivative and, if desired, derivatizing the resultant 7-amino taxol to give thereby a taxane derivative of formula II where the leaving group Re is replaced by a residue of formula NR₇R₈ where R₇ and R₈ are defined in claim 1;

(d) removing, if necessary, the said hydroxy protecting group R₅ from the resulting intermediate of formula III:

wherein R, is as defined in claim l and R₂, R₃, R₄ and R'₅ are as defined above,- and

(e) optionally salifying the resulting taxane derivative of the formula I to form a pharmaceutically acceptable salt thereof.

7. A compound of the formula III as defined in claim 6.

8. A process for preparing a compound of the formula III as defined in claim 6, which process comprises

(a) carrying out a substitution reaction with an azide or cyanide salt or a derivative thereof on a taxane derivative of formula II as defined in claim 6, thereby to form a taxane derivative having at the 7-position an azido, cyano or lH-tetrazol-5-yl group,*

(b) optionally reducing the said 7-azido derivative and, if desired, derivatizing the resultant 7-amino taxol to give thereby a taxane derivative of formula II where the leaving group R₆ is replaced by a residue of formula NR₇R₈ where R₇ and R₈ are defined in claim 1.

9. A phamaceutical composition which comprises a taxane derivative of the formula I as defined in any one of claims 1 to 5 or a pharmaceutically acceptable salt thereof together with a pharmaceutically acceptable diluent or carrier.

10. A taxane derivative of formula I as defined in any one of claims 1 to 5 or a pharmaceutically acceptable salt thereof for use as an antitumor agent.