Unusual terpenes with novel carbon skeletons from the West Indian sea whip Pseudopterogorgia elisabethae (Octocorallia)

From the hexane solubles of the West Indian gorgonian Pseudopterogorgia elisabethae collected near San Andres Island, Colombia, were isolated a marine diterpenoid, two nor-diterpenoids, and a bisnor-diterpenoid, all of which possess most unusual carbocyclic skeletons. The structures and relative configurations of novel metabolites elisabethinsA-C (1-3) and elisabanolide (4) were elucidated by interpretation of overall spectral data, which included 2D NMR correlation methods; IR, UV, and accurate mass measurements (HREIMS); chemical reactions; and X-ray diffraction analyses. One of these, elisabethin B (2), showed significant differential antitumor activity, and compounds 3 and 4 have weak in vitro antituberculosis activity.