Synthesis of a tetracyclic substructure of manzamine A

Abstract A synthesis of tetracyclic manzamine A substructure 28 is described. The route involves (1) a new approach to perhydroisoquinolines, (2) a Mitsunobu reaction that process with net retention of configuration using a new N-acyl sulfonamide ( 16 ) and (3) a high yield preparation of a Δ 3,4 -azocine via an intramolecular N-alkylation.