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Journal of the American Chemical Society, Vol.142, No.6, 3269-3274, 2020
Enantioselective Total Synthesis of (+)-Corymine and (-)-Deformylcorymine
We report herein the first enantioselective total synthesis of akuammiline alkaloids (+)-corymine and (-)-deformylcorymine. Starting from commercially available N-nosyltryptamine, the target molecules are both achieved in 11 steps. Key elements of the design include (a) a copper-catalyzed enantioselective addition of dimethyl malonate to a 3-bromooxindole to secure the C7 all-carbon quaternary stereocenter, (b) a one-step construction of cyclohexyl and pyrrolidinyl rings via intramolecular nucleophilic C- and N-addition, and (c) a nickel-promoted 7-endo cyclization of alkenyl bromide to furnish the azepanyl ring. The strategy is further extended to the synthesis of another three members of the akuammiline family, namely, (-)-10- demethoxyvincorine, (-)-2(S)-cathafoline, and (-)-3-epi-dihydrocorymine 17-acetate.