Iron-Catalyzed Synthesis of the Hexahydrocyclopenta[c]furan Core and Concise Total Synthesis of Polyflavanostilbene B

The first synthesis of polyflavanostilbene B (1), which has seven contiguous stereocenters including two quaternary carbon centers, from abundant polymeric (-)-epicatechin gallate on a gram scale in three steps without the use of protecting groups is reported. The key transformations of this strategy include a regioselective and stereoselective substitution of resveratrol to give the 4-derivative of (-)-epicatechin 3-gallate and an iron-catalyzed cyclization reaction. The possible radical cyclization mechanism in the formation of the hexahydrocyclopenta[c]furan core is also discussed.