Iterative Synthetic Strategy for Azaphenalene Alkaloids. Total Synthesis of (-)-9a epi-Hippocasine

A new strategy for the stereoselective synthesis of alkaloids with perhydro-9b-azaphenalene skeleton has been developed. The starting material is the substituted glutarimide derivative 1, readily available in either enantiomeric form through the palladium-catalyzed asymmetric allylic alkylation of glutarimide. The strategy relies on an iterative methodology encompassing two nucleophilic allylations and two ring closing metathesis processes. The approach has been used in the first synthesis of (-)-9a- epi-hippocasine.