Asymmetric Synthesis and Structure Revision of Guignardone H and I: Development of a Chiral 1,3-Diketone Possessing C2 Symmetry.

A novel chiral 1,3-diketone possessing C2 symmetry was synthesized and utilized in the asymmetric synthesis of guignardone H and I by employing sequential condensation-6π-electrocyclization reactions with the novel 1,3-diketone followed by stereoselective hydrogenation as key steps. Although the synthetic compounds differed from natural guignardone H and I, we realized that the C4-epimers of the proposed structures for guignardone H and I were the actual structures.