Enantioselective Total Synthesis of (+)-Flavisiamine F via Late-Stage Visible-Light-Induced Photochemical Cyclization

The structural features Kopsia alkaloids, in particular multiple all-carbon quaternary stereocenters in a caged and strained polycyclic skeleton, poses particular challenges for enantioselective total synthesis. Herein, we reported the first total synthesis of (+)-flavisiamine F. The synthetic approach involved a room-temperature Overman rearrangement for introducing the chiral amine at C21, a TMS-promoted ketal Claisen rearrangement for constructing the all-carbon quaternary stereocenter at C20, and a late-stage visible-light-induced photochemical cyclization for establishing the all-carbon quaternary stereocenter at C7.