Total Synthesis of (+)-Batzelladine A and (−)-Batzelladine D via [4 + 2]-Annulation of Vinyl Carbodiimides with <i>N</i>-Alkyl Imines

Abstract

A diastereoselective [4 + 2]-annulation of vinyl carbodiimides with chiral N-alkyl imines has been developed to access the stereochemically rich polycyclic guanidine cores of the batzelladine alkaloids. Application of this strategy, together with additional key steps such as long-range directed hydrogenation and diastereoselective intramolecular iodo-amination, led to highly convergent total syntheses of (-)-batzelladine D and (+)-batzelladine A with excellent stereocontrol.