Four new steroids from two octocorals

In search of analogues of isogosterones A-D (1-4), a group of antifouling 13,17-seco-steroids found in octocorals of the order Alcyonacea, we have isolated four new steroids possessing aromatic, enone, or dienone A-rings from two octocorals, Alcyonium gracillimum and Dendronephthya sp. These compounds, 3-methoxy-19-norpregna-1,3, 5(10),20-tetraene (5), 3-(4-O-acetyl-6-deoxy-beta-galactopyranosyloxy)-19-norpregna-1,3, 5(10),20-tetraene (6), 22,23-dihydroxycholesta-1,24-dien-3-one (7), and methyl 3-oxochola-4,22-dien-24-oate (8), showed no antifouling activity against barnacle (Balanus amphitrite) larvae, but lethality to barnacle larvae at a concentration of 100 &mgr;g/mL (LD(100)).