Total Synthesis of the Hamigerans.

The first total synthesis of hamigerans D, G, L, and N-Q has been accomplished. A convergent approach was used to build the basic tricarbocyclic ring system bearing a 5-6-6 structure. A sequence of oxidative cleavage, homologation, and ring regeneration provided access to the 5-7-6 skeleton of hamigeran G. Based on the biogenetic hypothesis, elegant and highly efficient biomimetic transformations of hamigeran G into hamigerans D, N-Q, and L were achieved.