STEREOSELECTIVE CONSTRUCTION OF THE DICYCLOPENTA[A,D]CYCLOOCTENE COREOF THE CEROPLASTIN SESTERTERPENES BY WAY OF THE ANIONIC OXY-COPE REARRANGEMENT

Bicyclo[3.2.1]octanediones such as 9, which are readily available by d ouble carbonylation of (1,3-cyclohexadiene)iron tricarbonyl complexes according to Eilbracht, are amenable to regiospecific methylenation un der Wittig conditions. Reduction of 10 with copper hydride leads to 11 , which can be resolved by application of Johnson's sulfoximine techno logy and oxidized to give the enantiopure antipodes of 10. Variously s ubstituted cyclopentenyl anions undergo 1,2-addition to 10, providing carbinols which are capable of anionic oxy-Cope rearrangement via chai r transition states. These structural reorganizations are fully stereo controlled and lead directly to functionalized dicyclopenta[a,d]cycloo ctenes. When 11 is treated analogously, only [1,3] sigmatropy is obser ved and inversion of stereochemistry at the migrating carbon prevails. Both processes exhibit impressive scaffolding powers and are characte rized by brevity.