Novel syntheses of (E)- and (Z)-volkendousin, cytotoxic steroids from the plant Melia volkensii

New syntheses of naturally occurring cytotoxic plant steroids (E)- and (Z)- volkendousin (1 and 2) and their acetonides 1a - a potent selective cell gr owth inhibitor - and 2a have been accomplished, starting from diosgenin (ov erall yields of 1.2%, 0.7%, 1.9%, and 1.1% for 1, 2, 1a, and 2a, respective ly), and also from 16-dehydropregnenolone (overall yields of 9.4%, 2.5%, 14 .0%, and 3.8% for 1, 2, 1a, and 2a, respectively). The efficiency of the st ereospecific Petrow rearrangement and the straightforward introduction of t he alpha,beta-unsaturated ketone functionality, by a Wharton reaction, illu strate the utility of this new synthetic strategy.