CEMBRANOID DITERPENES RELATED TO SARCOPHYTOL-A FROM THE SOFT CORAL SARCOPHYTON-TROCHELIOPHORUM (ALCYONACEA)

An investigation of metabolites from the soft coral Sarcophyton troche liophorum collected at North East Reef, Orpheus Island, has yielded th ree simple cembranoid diterpenes, namely ,14S,1E,3E,11E)-7,8-epoxycemb ra-1,3,11-trien-14-ol (1), E,3E,11E)-14-acetoxy-7,8-epoxycembra-1,3,11 -triene (2) and S,1E,3E,8E,11E)-cembra-1,3,8,11-tetraene-7,14-diol (3) , together with the known dihydrofuran sarcophytoxide (4). The diterpe nes (2) and (3) were previously reported as synthetic derivatives of s arcophytol A, but this is the first report of their natural occurrence . The three mildly cytotoxic diterpenes (1)-(3) are structural modific ations of the antitumour promotor sarcophytol A (5). Structures were e stablished by high-resolution n.m.r. spectroscopy and interconversion. The absolute stereochemistries of the metabolites were determined by use of the Mosher n.m.r. method, and the stereochemistry at C14 was sh own to be the same as that of sarcophytol A in each case. These result s are in agreement with the published absolute stereochemistries of th e metabolites determined by the Horeau method. Full n.m.r. assignments for (11S,12S,14S,1E,3E,7E)-11,12-epoxycembra- 1,3,7-trien-14-ol (6) a nd E,3E,7E)-14-acetoxy-11,12-epoxycembra-1,3,7-triene (7) are given.