Total Synthesis of (+)-Dendrowardol C

The first total synthesis of the tetracyclic sesquiterpenoid (+)-dendrowardol C is described. It relies on an intramolecular aldol reaction to forge the central bicyclic scaffold and subsequent cyclobutane formation by cyclization of a γ-triflyloxy ketone. Key is the treatment of the latter with lithium naphthalenide. Finally, the diastereoselective hydroboration of a 1,1-disubstituted double bond is enabled by a chiral CoI catalyst.