Novel terpenoids from the West Indian sea whip Pseudopterogorgia elisabethae (Bayer). Elisapterosins A and B: Rearranged diterpenes possessing an unprecedented cagelike framework

Four diterpenes and a nor-diterpenoid, all of which possess unusual carbocy clic skeletons, were isolated from the hexane solubles of the West Indian g orgonian Pseudopterogorgia elisabethae. The structures and relative configu rations of novel metabolites elisabethin D (2), elisabethin D acetate (3); 3-epi-elisabanolide (5), elisapterosin A (6), and elisapterosin B (7) were elucidated by interpretation of overall spectral data, which included 2D NM R correlation methods, IR, UV, and accurate mass measurements (HREI-MS and HRFAB-MS), chemical reactions, and X-ray diffraction analyses. The tetracyc lic carbon skeleton of the elisapterosins is undescribed and constitutes a new class of C-20 rearranged diterpenes, Elisapterosin B displays strong in vitro anti-tuberculosis activity.