Three new diterpenes have
been isolated from soft corals of the genus Efflatounaria (Coelenterata, Octocorallia, Alcyonacea, Xeniidae). The
structure of the first compound (4) was elucidated on the basis of high-field 1H
n.m.r. spectroscopy while that of the second metabolite (5) was determined by
single-crystal X-ray analysis. The third diterpene
(6) was structurally related to (5), and its structure was confirmed by
chemical transformation. All three diterpenes can be derived from xenicin-type precursors, by cleavage and recyclization.