Transformation of santonin into(+)-deoxyvernolepin and related dilactones

Abstract

Ozonolysis followed by acetylation of the (3S,3aS,5aR,9R,9aS,9bS)-5a-hydroxymethyl-2-methoxy-3,9-dimethyl-2,3-decahydronaphtho[1,2-b]furan (7) derived from (–)-α-santonin gave an unexpected product, (3S,3aS,6R,7S,7aS)-7-[(S)-2-formylethyl]-2-methoxy-3-methyloctahydrobenzofuran-6-spiro-3′-furan-5′-one (13), which served as the key intermediate for the synthesis of (+)-deoxyvernolepin (2) and related unsaturated lactones (4)–(6). Some unsaturated lactones obtained were submitted to a preliminary test for antitumour activity.