Studies on Pumiliotoxin A Alkaloids: An Approach to Preparing the Indolizidinic Core by Intramolecular Diastereoselective N-Heterocyclic Carbene Catalyzed Benzoin Reaction

In this article, we describe the development of a convergent organocatalytic strategy to prepare the indolizidinic core of the pumiliotoxin A alkaloid family. The key step of the proposed strategy is based on a diastereoselective N-heterocyclic carbene catalyzed benzoin reaction, in which the Breslow intermediate generated from an enal moiety (umpolung a(1) to d(1) - acyl anion equivalent) attacks a ketone moiety intramolecularly to provide the indolizidinone core in good yield with good selectivity. (AU)