Heck Cyclization Strategy for Preparation of Erythrinan Alkaloids: Asymmetric Synthesis of Unnatural (-)-Erysotramidine from L-Tartaric Acid

With an imide derived from l-tartaric acid as the starting material, ent-erysotramidine was synthesized for the first time. The synthesis features the use of the enantiopure synthon, prepared in a set of highly stereoselective reactions, including N-acyliminium cyclization, dihydrofuranyl ring formation via silver-catalyzed intramolecular alcohol addition to acetylene, and vinyl ether catalytic hydrogen reduction. The crucial step of the synthesis, assembly of ring A, was achieved by using Heck cyclization of (Z)-iodoolefin.