Five new eunicellin-type diterpenoids, briarellins E--I, along with several known diterpenoids of the asbestinane, briarane and eunicellane classes, were isolated from the Caribbean gorgonian octocoral Briareum asbestinum collected in Puerto Rico. The structures of these compounds were established on the basis of spectroscopic evidence.

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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.

Sixteen new diterpenoids, representative of the asbestinane skeletal class, have been isolated from shallow water colonies of the Caribbean gorgonian octocoral Briareum asbestinum. The structures of these secondary metabolites, named asbestinin-11 [1], asbestinin-12 [3], asbestinin-13 [4], asbestinin-14 [5], asbestinin-15 [7], asbestinin-16 [8], asbestinin-17 [9], asbestinin-18 [10], asbestinin-19 [11], asbestinin-20 [12], asbestinin-21 [13], asbestinin-22 [14], asbestinin-23 [15], 11-acetoxy-4-deoxyasbestinin E [16], 11-acetoxy-4-deoxyasbestinin F [17] and 4-deoxyasbestinin G [18], were defined by chemical and spectroscopic methods. These specimens of B. asbestinum, collected in Puerto Rico, yielded almost exclusively diterpenoids possessing the asbestinane carbon skeleton thus suggesting minor biosynthetic variations for this gorgonian. In this paper, we also revise the structures of the known asbestinin-6 and asbestinin-7 to asbestinanes 2 and 6, respectively.

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