Concise total synthesis of spirocurcasone.

A concise total synthesis of spirocurcasone was accomplished. Key features of the synthesis involved a vinylogous Mukaiyama aldol reaction, a Carroll rearrangement of β-keto allyl ester derivative, an intramolecular aldol condensation, and a spiro ring formation by ring-closing metathesis of the pentaene compound. This synthetic work was complete in nine steps from (S)- or (R)-perillaldehyde without the use of protecting groups. Interestingly, the optical rotation of the synthetic spirocurcasone was different from the reported value of the natural product.