Taxoids, their preparation and the pharmaceutical compositions which contain them

Claim 1

A process for preparing taxoid derivatives of formula II; ##STR12## wherein Ar represents an aryl radical, R 1 represents a benzoyl radical or a radical R 2 --O--CO-- in which R 2 represents: a straight or branched 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 11 carbons atoms, these radicals unsubstituted or substituted by at least one substituent selected from halogen atoms and hydroxyl radicals, alkyloxy radicals containing 1 to 4 carbon atoms, dialkylamino radicals in which each alkyl part contains 1 to 4 carbon atoms, piperidino radicals, morpholino radicals, 1-piperazinyl radicals (unsubstituted or substituted in the 4-position by an alkyl radical containing 1 to 4 carbon atoms or by a phenylalkyl radical in which the alkyl part contains 1 to 4 carbon atoms), cycloalkyl radicals containing 3 to 6 carbon atoms, cycloalkenyl radicals containing 4 to 6 carbon atoms, phenyl radicals, cyano radicals, carboxyl radicals, or alkoxycarbonyl radicals in which the alkyl part contains 1 to 4 carbon atoms; or by a phenyl radical unsubstituted or substituted by at least one atom or radical selected from halogen atoms, alkyl radicals containing 1 to 4 carbon atoms, or alkyloxy radicals containing 1 to 4 carbon atoms; or by a saturated or unsaturated heterocyclyl radical containing 4 to 6 members and unsubstituted or substituted by at least one alkyl radical containing 1 to 4 carbon atoms; and R 3 represents: a straight or branched 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 11 carbons atoms, these radicals unsubstituted or substituted by at least one substituent selected from halogen atoms and hydroxyl radicals, alkyloxy radicals containing 1 to 4 carbon atoms, dialkylamino radicals in which each alkyl part contains 1 to 4 carbon atoms, piperidino radicals, morpholino radicals, 1-piperazinyl radicals (unsubstituted or substituted in the 4-position by an alkyl radical containing 1 to 4 carbon atoms or by a phenylalkyl radical in which the alkyl part contains 1 to 4 carbon atoms), cycloalkyl radicals containing 3 to 6 carbon atoms, cycloalkenyl radicals containing 4 to 6 carbon atoms, or phenyl radicals, unsubstituted or substituted cyano radicals, carboxyl radicals, alkoxycarbonyl radicals in which the alkyl part contains 1 to 4 carbon atoms, or alkyl radicals containing 1 to 4 carbon atoms; or an aryl radical unsubstituted or substituted by at least one atom or radical selected from halogen atoms, alkyl radicals containing 1 to 4 carbon atoms, and alkyloxy radicals containing 1 to 4 carbon atoms, wherein R 3 cannot represent an unsubstituted phenyl radical; or a saturated or unsaturated heterocyclyl radical containing 4 to 6 members and unsubstituted or substituted by at least one substituent selected from halogen atoms, alkyl radicals containing 1 to 4 carbon atoms, or alkoxy radicals of 1 to 4 carbon atoms; either R 4 represents a hydrogen atom and R 5 represents a protecting group of the hydroxyl functional group or R 4 and R 5 together form a saturated 5- or 6-membered heterocycl group, G 1 represents a protecting group of the hydroxyl functional group, and G 2 represents an acetyl radical or a protecting group of the hydroxyl functional group; comprising electrolytically reducing a product of formula VIII: ##STR13## wherein Ar and R 1 are defined as above, R' 5 represents a hydrogen atom or a protecting group of the hydroxyl functional group, R 4 represents a hydrogen atom, G' 1 represents a hydrogen atom or a protecting group of the hydroxyl functional group, and G' 2 represents a hydrogen atom, an acetyl radical, or a protecting group of the hydroxyl functional group; wherein the electrolytic reduction is performed in an electrolyte comprising a quaternary ammonium salt which is soluble in an organic solvent or in an aqueous/organic mixture at a controlled potential.