New route to azaspirocycles via the organolithium-mediated conversion of beta-alkoxy aziridines into cyclopentenyl amines.

A new three-step route to azaspirocycles involving the organolithium-mediated conversion of beta-alkoxy aziridines into substituted cyclopentenyl amines, hydroboration, and cyclization has been developed. The methodology is utilized in the construction of the pentacyclic ring system of cephalotaxine. [reaction: see text]