Intramolecular Mannich Reaction in the Asymmetric Synthesis of Polysubstituted Piperidines: Concise Synthesis of the Dendrobate Alkaloid (+)-241D and Its C-4 Epimer

The intramolecular Mannich reaction of δ-amino β-keto esters with aldehydes and ketones is a new methodology for the synthesis of polysubstituted piperidines and is illustrated by the concise asymmetric synthesis of the dendrobate alkaloid (+)-241D and its C-4 epimer.