Studies of Australian soft corals. VII. Two new diterpenes from an unknown species of soft coral (genus Lobophytum)

Abstract

Two new diterpenes have been isolated from a soft coral of the genus Lobophytum. One is shown to be a cembranolide diterpene (1) containing a novel a-keto epoxide grouping while the second compound (2) is unique in the soft coral literature in that it possesses a 13-membered carbocyclic ring. This was presumably derived from rearrangement of (1) within the coral. The structure assignments rely heavily on spectroscopy, but are consistent with chemical transformations.