Reactions and intermediates of use in syntheses of compounds of the 2-dehydroemetine series

摘要

FORM:1059326/C2/1 The invention comprises: (a) compounds of the general Formula (Va), wherein R1 and R2 are aliphatic, aromatic or araliphatic hydrocarbon groups, R3 and R4 are carbonyl protecting groups or together constitute a single bivalent protecting group, R5 is hydrogen and R6 hydrogen or a hydroxy or acyloxy group or R5 and R6 together form a ketonic oxygen atom, and wherein, and in all the other general formulae, the benzene rings are unsubstituted or substituted with one or more aliphatic, araliphatic or aromatic ether or hydrocarbon groups (including methylenedioxy groups but especially methoxy groups in the 61-, 71-, 9-and 10-positions); (b) the preparation of compounds of the general Formula (III) by treating a compound of the general Formula (IV) with a reducing agent serving to reduce a carbonyl group to a secondary alcohol group; (c) the combination of the process of (b) with the preparation of the starting material by the action of a ketone-protecting agent on a compound of the general Formula (I) or (V), followed in the latter case by the action of a dehydrating agent; and (d) the preparation of compounds of the general Formula (II) by following (b) or (c) with, in various sequences, the steps of (i), acylation of the 3-hydroxyalkyl group, (ii) reduction of the resulting 3-acyloxyalkyl group to an alkyl group, (iii) removal of the ketone-protecting group, and (iv) removal of the 21-position side chain.