PROCESS FOR PREPARING VINBLASTINE DERIVATIVES

A process for the preparation of new cytostatic compounds of general formula (I> in which either R represents a beta -hydroxyl group and R represents an alpha -ethyl group or R represents a hydrogen atom and R represents a beta -ethyl group; R'' represents a methyl group, a straight chain alkyl group having from 3 to 10 carbon atoms, a branched chain alkyl group having from 3 to 10 carbon atoms and in which the carbon atom attached to the group has a primary or secondary configuration, or an aralkyl having from 1 to 3 carbon atoms in the alkyl moiety; R represents a methoxy group; and R represents an acetyl group; which comprises reacting a compound of formula (II), (in which R , R , R and R are as defined above), or an acid addition salt thereof with a large excess of an alcohol of formula R''-OH (III> (wherein R'' is as defined above) in the presence of chromium trioxide at a temperature of from -60 DEG C to -30 DEG C.