Intramolecular radical allylation with allylic sulfones - A synthesis of (+/-)-botryodiplodin

Isopropenyl-5-membered-ring acetal or lactone are potential precursors of ( +/-)-borryodipiodin (1). Several pathways, involving 5-ero-trig ring closur e onto allylic sulfones, have been investigated. The iodine atom transfer m ethodology allowed the preparation of the desired skeleton through intramol ecular addition of an alpha-alkoxycarbonyl radical to the double bond of th e appropriate allylic ethyl sulfone. subsequent deprotonation and kinetic r eprotonation led to the key precursor 14 with a high stereoselectivity. (C) 1999 Elsevier Science Ltd. All rights reserved.