Asymmetric Total Synthesis of ent‐Pyripyropene A

Abstract An asymmetric total synthesis of ent ‐pyripyropene A was achieved by a convergent synthetic route. We used our originally developed Ti III ‐catalyzed radical cyclization to construct an AB‐ring portion that consisted of a trans ‐decalin skeleton with five contiguous stereogenic centers. The coupling between the AB‐ring and the DE‐ring portions, and a subsequent C‐ring cyclization, led to the total synthesis of ent ‐pyripyropene A. An evaluation of the insecticidal activity of ent ‐pyripyropene A against two aphid species revealed that ent ‐pyripyropene A was 35–175 times less active than naturally occurring pyripyropene A. This result indicated that the biological target of pyripyropene A recognizes the absolute configuration of pyripyropene A.