Restructuring α -pinene: novel entry into diverse polycarbocyclic frameworks

(-)-α-Pinene 1 has been restructured into a chiral cyclohexenone (+)-6, in which the functionalities were integrated to afford bicyclo[3.3.1]nonan 3,7-diones and a novel tricyclic skeleton 16 related to the sesquiterpene clovene. Intramolecular [2+2] photocycloadditions in (+)-6 and related 5-alkenylcyclohexenones provided an entry into some novel bridged tricyclic systems