Stereoselective synthesis of the fully functionalized core fragment of terpentecin

A stereoselective synthesis of the core fragment 4 of terpentecin is presented. The five contiguous asymmetric centers of 4 were prepared from enone 8 via a sequence of steps highlighted by: oxygenation of the C6 center by epoxidation of enone 18, methylenation of the C8 carbonyl group of 20 by means of the Peterson olefination, stereoselective construction of the C8 center of 21 using homogeneous catalytic hydrogenation and stereoselective oxygenation of the C7 center.