SYNTHETIC STUDIES ON WEDELIGENIN - PREPARATION OF AN A/B-RING INTERMEDIATE

In a new approach to the synthesis of wedeligenin, an A/B-ring intermediate (13a) has been synthesized. The beta-keto ester (15) was readily prepared from Wieland-Meischer ketone in three steps. Baeyer-Villiger oxidation of (15) and subsequent methylenation provided an alkene (16) which contained the malonyl substituent, later to become the gem-diester of (13a). Regiospecific conversion of the alkene into a bromohydrin followed by cyclization afforded (13a). This provided an A/B-ring intermediate which could be further elaborated to allow C/D-ring annulation.