Asymmetric Total Synthesis of (-)-Stemonamine and Its Stereochemical Stability.

The first asymmetric total synthesis of (-)-stemonamine is described. The key reactions included intramolecular acylation to construct the seven-membered ring and a tandem [2+2] cycloaddition-Dieckmann condensation reaction using an ynolate to form the fully substituted cyclopentenone moiety. Racemization and epimerization of the natural product were first experimentally demonstrated.