Abstract The chemical behavior of latrunculins A (1) and B (2)(Lat A and B) under a variety of reaction conditions is described. The combination of the macrolide, the THP-lactol, and the 2- thiazolidinone rings was found to result in interesting unpredicted chemical transformations. The structures of two new Lats, 6, 7-epoxy-Lat A (3) and Lat M (4) isolated from Latrunculia magnifica are discussed.