Further synthetic studies towards the austrodorane skeleton: synthesis of austrodoral.

The synthesis of austrodoral (1), a marine nor-sesquiterpene that contains a unique bicyclic skeleton, has been achieved. The synthetic strategy is based on the ring contraction of a suitable optically active drimanic epoxy derivative, obtained from commercially available (+)-sclareolide (4). Fluorosulfonic acid was found to promote the ring contraction efficiently. The nor-sesquiterpene hydrocarbon 13, a key intermediate in the synthesis of sesquiterpene hydroquinones, has also been prepared in optically active form.