This invention relates to a method of preparing taxane derivatives of formula (I) by esterification of protected baccatin III or 10-deacetylbaccatin III by means of an acid of formula (VII), elimination of protection groupings and acylation of the amine function of the side chain. The products of formula (I) have remarkable antitumor and antileukemia properties. In formulae (I) and (VII): Ar stands for aryl, R is hydrogen or acetyl, R.sub.1 is a benzoyl radical or an R.sub.2 --O--CO-- radical in which R.sub.2 is alkyl, alkenyl, alkynyl, cycloalkyl, cycloalkenyl, bicycloalkyl, phenyl or heterocyclyl, R.sub.3 is a trihalomethyl radical or phenyl substituted by a trihalomethyl radical, R.sub.4 is a hydrogen atom or is the same as R.sub.1. ##STR1##