Enantioselective Total Synthesis of Bipolarolides A and B

Bipolarolides A and B are members of the ophiobolin family of sesterterpenes, characterized by their intricate cage-like structures. Herein we report a concise asymmetric total synthesis of bipolarolides A and B enabled by the type-II Diels-Alder reaction. The synthesis features a sequence of key transformations: an iridium-catalyzed enantioselective allylation to establish the first stereocenter, type-II Diels-Alder reaction to rapidly assemble the bicyclo[3.3.1]non-1-ene core, reductive oxy-ring opening with olefin isomerization, aldol cyclization to construct a D ring, and a late-stage electrochemical C-H oxidation to complete the ether ring.