Formal total synthesis of (-)-haouamine A

摘要

A largely catalysis based approach to optically active haouamine A (-)-l is presented, which provides the hexacyclic compound 25 previously used to construct this cytotoxic marine alkaloid. Haouamine A (1) and B (2) isolated from the marine ascidian Aplidium haouarianum collected off the coast of southern Spain represent an unorthodox new class of alkaloids.1 They consist of a congested indeno-tetrahydropyridine unit fused to an 11-membered paracyclophane moiety which is so strained that one of its phenol rings is forced out of planarity to adopt a pseudo-boat conformation. The synthetic challenges posed by this intricate topology are further increased by an anti-Bredt double bond contained within the heptacyclic framework as well as by the all-carbon quaternary chiral center at C-26.