Asymmetric total syntheses of (+)-coronafacic acid and (+)-coronatine, phytotoxins isolated from Pseudomonas syringae pathovars

Asymmetric total synthesis of (+)-coronafacic acid (2), was accomplished via intramolecular 1, 6-conjugate addition as the key step. The chiral ester (+)-7 was prepared via two approaches: starting from (R)-(+)-4-acetoxy-2-cyclopenten-1-one (12), and using catalytic asymmetric Michael reactions promoted by heterobimetallic BINOL complexes. Coupling between (+)-2 and the protected coronamic acid 8 and subsequent deprotection by hydrogenolysis provided (+)-coronatine (1). This is the first asymmetric total synthesis of (+)-1. (C) 1997 Elsevier Science Ltd.