DEVELOPMENT OF NOVEL SKELETAL TRANSFORMATIONS AND THEIR APPLICATION TO SYNTHESIS OF TERPENOIDS

Novel skeletal transformations of bicyclo[4.2.0]octan-2-ones via 8-mem bered-ring carbocation intermediates have been developed. The acid-cat alyzed rearrangement of 5,6-disubstituted bicyclooctanones is a highly -efficient method for synthesis of polycyclopentanoids such as diquina nes, angularly-fused triquinanes, spiro-annulated triquinanes, and tet raquinanes. The reaction of 5-6-4 fused ring ketones with acid in acid anhydride is a unique method for construction of 8-membered-ring comp ounds such as bicyclo[6.3.0]undecanes. The acid-catalyzed rearrangemen t of 6-substituted bicyclooctanones provides an excellent method for s ynthesis of bicyclo [4.2.1]nonanes. Utility of our novel method has be en demonstrated by synthetic studies of terpenoids such as 5-oxosilphi perfol-6-ene, silphiperfol-6-ene, 3-oxosilphinene, and mediterraneol B .