Stereocontrolled elaboration of quaternary carbon centers involving the asymmetric michael-type alkylation of chiral imines: an efficient enantioselective access to (+)-vincamine

Abstract

Michael adduct (S)- 5 b , resulting from the condensation of chiral imine 4 with methyl acrylate, was transformed in two steps into lactone (S)- 8 b . Tryptamine-induced ring-opening of this lactone gave 9, which was finally converted in three steps into the key tricyclic derivative (S)- 11 b , a known precursor of (+)-vincamine 1.