Briareins C-L, 10 new briarane diterpenoids from the common Caribbean gorgonian Briareum asbestinum

Ten new diterpenoid representatives from the briarane skeletal class have been isolated from shallow water colonies of the Caribbean gorgonian octocoral Briareum asbestinum collected at Mona Island near Puerto Rico. The structures of the new secondary metabolites, named briareins C-L (3-12), were defined by chemical and spectroscopic methods. In addition, two known diterpenoids, briareins A (1) and B (2), were among the most abundant compounds isolated. Traces of another known diterpenoid, briarane methyl ester (13), were also isolated from the same gorgonian extracts. In this paper we also-establish unambiguously structure 2 for the known diterpene briarein B.