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

In a new approach to the synthesis of wedeligenin, an A/B-ring interme diate (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-die ster of (13a). Regiospecific conversion of the alkene into a bromohydr in followed by cyclization afforded (13a). This provided an A/B-ring i ntermediate which could be further elaborated to allow C/D-ring annula tion.