Asymmetric Total Synthesis of Propindilactone G, Part 2: Enantioselective Construction of the Fully Functionalized BCDE Ring System

The enantioselective synthesis of the fully functionalized BCDE tetracyclic ring system of propindilactone G ( A ) is reported. Several synthetic methods were developed and applied to achieve this goal, including: 1) an asymmetric Diels–Alder reaction in the presence of Hayashi′s catalyst for the synthesis of optically pure key intermediate 3 ; 2) an intramolecular Pauson–Khand reaction (PKR) for the stereoselective synthesis of the BCDE ring with an all‐carbon chiral quaternary center at the C13 position by using the TMS‐substituted acetylene as the substrate; and 3) Pd‐catalyzed reductive hydrogenolysis for the stereoselective synthesis of the fully functionalized BCDE tetracyclic ring system. The chemistry developed herein provided a greater understanding of the total synthesis propindilactone G ( A ) and its analogues.