An efficient synthesis of optically active physostigmine from tryptophan via alkylative cyclization

[GRAPHICS] A new and efficient synthetic route to physostigmine is described. Corey-Kim reagent reacted with tryptamine or tryptophan carbamates to give 3a-(methylthiomethyl)hexahydropyrrolo[2,3-b]indole skeletons. Formal total synthesis of racemic and chiral physostigmine was accomplished in excellent overall yields, in short steps.