A Formal Synthesis of Porantheridine and an Epimer

A formal synthesis of porantheridine and a synthesis of its C6-epimer have been completed, employing silver-catalyzed allene cyclization to form a common cis-isoxazolidine intermediate and related N-acyl iminium ion intermediates for side-chain introduction. The stereochemistry of this step can be controlled by choice of the N-protection method.