Note
The gorgonian coral Briareum asbestinum (Pallas) (Briareidae), occurring in Caribbean waters, contains diterpenes of two skeletal types, the asbestinins and the briareins, some of which are endowed with biological activity (1, 2). Several chlorinated briareins have also been isolated, and the absolute structure of one of them, briarein A [1], a pentaacetate, has been determined by X-ray (3). Subsequently, a related species Briareum polyanthes, found off Bermuda, was examined. Three metabolites possessing the epoxybriarein structure, but designated as briantheins X [2], Y [3], and Z [4] were identified (4, 5). [The structure of Brianthein W, a less fuctionalized nonchlorinated briarein, has been recently determined (6).]