Asymmetric Total Synthesis of Propindilactone G.

A concise total synthesis of (+)-propindilactone G, a nortriterpenoid isolated from the stems of Schisandra propinqua var. propinqua, has been achieved for the first time. The key steps of the synthesis include an asymmetric Diels-Alder reaction, a Pauson-Khand reaction, a Pd-catalyzed reductive hydrogenolysis reaction, and an oxidative heterocoupling reaction. These reactions enabled the synthesis of (+)-propindilactone G in only 20 steps. As a consequence of our synthetic studies, the structure of (+)-propindilactone G has been revised.