A new marine epoxy prostanoid with an antiproliferative activity from the stolonifer Clavularia viridis Quoy and Gaimard.

Recently octocoral-derived marine prostanoids, clavulones 1) (claviridenones) 2) and their halogenated congeners, 3) have received much interest owing to their unique structural features and great antitumor activities. 3a,c,d,4) During our continuing investigations on marine prostanoids from the Japanese stolonifer Clavularia viridis Quoy and Gaimard from which clavulones and their halogenated congeners were found, we have isolated a new antiproliferative prostanoid 1, which is the first encounter of a natural prostanoid having a 1,2-epoxide ring. This paper describes the isolation and structure of 1. The freeze-dried organisms (1.2 kg) of Clavularia viridis 5) were extracted with hexane. The hexane extract (22.6 g) was repeatedly chromatographed on a silica gel column using a hexane-ethyl acetate mixture as an eluent. This gave the eluate containing the compound 1 and other halogenated prostanoids (chlorovulones, 3a) bromovulone I , 3c) and iodovulone I 3c) ) prior to the elution of clavulones. 1) High pressure liquid chromatography [silica gel, hexane-ether (2:1)] of the eluate gave 1 6) [colorless oil, 10 mg, C21H29ClO5, [ƒ¿]D -24.1•‹ (c 0.44, CHCl3)], iodovulone I, bromovulone I, and chlorovulones, in that order of increasing polarity. The UV spectrum (EtOH) of 1 showed an absorption at 300 rim (ƒÃ 4300) due to the conjugated dienone system. But there was no absorption due to the conjugated cyclopentenone system which is common in clavulones and their congeners. The IR spectrum (CHCl3) showed absorptions due to a hydroxy group (3580 cm -1 ), an ester group (1740 cm-1), and an ct-chlorocyclopentanone moiety conjugated with the diene system (1740, 1625 cm-1). The 1H-NMR spectrum (400 MHz, CDCl3) of 1 showed the signals due to the above-mentioned conjugated dienone system [ƒÂppm 6.13 (1H, tdd, J = 7.9, 10.9, 1.0