An enantiospecific synthesis of the antitumor marine sponge metabolite puup
ehedione (2a) and its C-8-epimer 2b as their methylenedioxy derivatives 8a
and 8b was achieved through concomitant O-allyl deprotection and electrocyo
lization of 20 derived from (-)-carvone. (C) 2001 Published by Elsevier Sci
ence Ltd.