Enantioselective Total Synthesis of (−)-Pavidolide B

The enantioselective synthesis of (−)-pavidolide B (1) was achieved in a linear sequence of 10 steps. The key steps are (a) an enantioselective organocatalytic cyclopropanation; (b) a radical-based cascade annulation for the regio- and diastereo-selective synthesis of the highly functionalized lactone 3 bearing the characteristic tricyclic core and seven contiguous stereocenters; (c) a sequential ring-closing metathesis reaction and a RhCl3-catalyzed double bond isomerization to form the seven-membered D ring of (−)-pavidolide B.