An approach to the synthesis of the manzamine alkaloids via the vinylogous amide pHotocycloAddition/retro-mannich fragmentation/Mannich closure cascade (pharM)

Article abstract of DOI:10.1002/ijch.199700008

The application of the vinylogous amide [2+2] photocycloaddition/ retro-Mannich fragmentation/Mannich closure cascade (pharM) to the synthesis of the pentacyclic ring system of the anti-leukemic marine alkaloid manzamine A is presented. Two approaches to the synthesis of the requisite pentacycle are described: (a) the transannular photocycloaddition of an 18-membered vinylogous amide; and (b) photocycloaddition of an acyclic vinylogous amide, followed by macrolactamization of the derived pharM closure product to generate the pentacyclic ring system.