A new strategy for the synthesis of (+)-vernolepin related compounds: an unusual sulfene elimination leads to the 2-oxa-cis-decalin skeleton

A new strategy for the synthesis of (+)-vernolepin (1), (+)-vernodalin (2), and (+)-8-deoxyvernolepin (3), from the accessible germacrolides (+)-salonitenolide (4) and (+)-costunolide (5), has been developed. The key steps in the synthesis are a Cope rearrangement from the germacradiene to the elemadiene skeleton, the cyclization of a trans-fused δ-lactone from an epoxy ester, and an unusual sulfene elimination, which promotes a reaction cascade leading to the 2-oxa-cis-decalin skeleton.