First total syntheses of bicyclic marine sesquiterpenoids drechslerines A and B

The first total syntheses of the bicyclic sesquiterpenoids drechslerines A (1) and B (2), which were isolated from the algicolous fungus Drechslera dematioidea in the marine red alga Liagora viscida, has been accomplished starting from (S)-carvone (13) via three palladium-catalyzed reactions, namely, diastereoselective allylation, conjugate reduction, and carbon monoxide insertion, as the key reactions.