Asymmetric Construction of Quaternary Carbon Centers by Sequential Conjugate Addition of Lithium Amide and in Situ Alkylation: Utility in the Synthesis of (-)-Aspidospermidine

Chiral diether ligand-controlled asymmetric conjugate addition of a lithium amide to cyclopentenecarboxylate and subsequent in situ alkylation gave a chiral cyclopentane derivative bearing a quaternary carbon with high enantio- and diastereoselectivity. The cyclopentane derivative was converted successfully to (-)-aspidospermidine.