Rumphellclovanes C–E, new clovane-type sesquiterpenoids from the gorgonian coral Rumphella antipathies

Three new clovane-related sesquiterpenoids, rumphellclovanes C–E (1–3), and a new natural clovane, clovan-2,9-dione (4), were isolated from a gorgonian coral Rumphella antipathies. The structures of clovanes 1–4 were elucidated by spectroscopic methods and by comparison of the spectral data with those of related analogues. Rumphellclovane C (1) was proven to be the first clovane-type sesquiterpenoid containing an ε-lactone moiety. A plausible biosynthetic pathway between clovanes 1 and 2 was proposed. Clovane 4 displayed significant inhibitory effects on the generation of superoxide anion and the release of elastase by human neutrophils.