Enantioselective Total Synthesis of (−)-Walsucochin B

The
first enantioselective total synthesis of the structurally
unique nortriterpenoid (−)-walsucochin B has been accomplished
through the cationic polyolefin cyclization initiated by chiral epoxide.
The core framework and the stereocenters in the natural product were
all constructed in this step. A site-selective, late-stage free-radical
halogenation and Seyferth–Gilbert homologation was adopted
to install the acetylene moiety to synthesize the phenylacetylene.
The absolute configuration of walsucochin B was confirmed through
enantioselective total synthesis.