SYNTHETIC STUDIES ON COLCHICINE - REACTION OF HOMOMORPHINANDIENONES

For the purpose of synthetic approaches toward colchicine (2) from O-m ethylandrocymbine (1a), reaction of homomorphinandienones (1a,b) was c arried out. Oxidation of 1a,b with 35% aqueous hydrogen peroxide gave a separable diastereomeric mixture of N-oxides (5,6). Polonovski react ion of the N-oxides (5) with acetic anhydride in CH2Cl2 afforded N-dem ethyl-N-acetamide (7a), whereas that of 5 and 6 with acetic anhydride in the presence of triethylamine gave enamines (8a,b) together with N- demethyl-N-acetamides (7a,b). Furthermore, reaction of enamines (8a,b) with N-bromosuccinimide in dimethoxyethane-H2O or methanol produced a -bromo amides (9a,b).