Aust. J. Chem., 1978,31, 2707-12 Studies of Australian Soft Corals. X* The Isolation of Epoxyisoneocembrene-A from Sinularia grayi and Isoneocembrene-A from Sarcophyton ehrenbergi Bruce F. owd den,*,^ John C. Coil,* Warren ~ i c k s , * Rymantas ~ a z l a u s k a s ~ and Sarah Jane MitchellA A Department of Chemistry and Biochemistry, James Cook University of North Queensland, Townsville, Qld. 481 1. Author to whom correspondence should be addressed. Roche Research Institute of Marine Pharmacology, P.O. Box 255, Dee Why, N.S.W. 2099. Abstract The isolation of an epoxyisoneocembrene-A [(E,E,E)-l1,12-epoxy-l-isopropyl-4,8,12-trimethylcyclo- tetradeca-1,3,7-triene] (I), from the soft coral Sinularia grayi, is reported and its structure demon- strated by chemical and spectroscopic means. The isolation of an isomer of the reported cembrene sarcophytoxide (2) and of isoneocembrene-A (3), an isomer of the termite trail pheromone neo- cembrene-A, from the soft coral Sarcophyton ehrenbergi is also reported. Chemical transformations enabled (1) to be converted into (3). The egg cowrie ( O d a ovum Linnaeus, 1758) is reported1 to feed on soft corals. We were thus interested to find a cluster of these animals cropping soft coral in Pioneer Bay, Great Palm Island, and returned to ppH 13 14 the laboratory with a large sample of the 10 12 coral, Sinularia grayi Tixier-Durivault,? and one specimen of the egg cowrie. Sepa- rate extraction of the freeze-dried coral and cowrie confirmed, by t.l.c., that the cowrie did indeed eat considerable amounts of the coral. In fact, the principal component in each extract, when one disregards the vast amounts of lipid present, was the cembran- oid diterpene whose structure we show to be (1). Corals are reported to be one of the important organisms in fat storage in the ocean^,^ and those which are not pro- tected by toxic chemicals3 are an important food source. Sinularia grayi is clearly not toxic to cowries. The diterpene (I), C,,H,,O, was isolated in 0.2% yield (based on the weight of freeze-dried coral) from the dichloromethane extract of the freeze-dried coral Sinularia grayi. The structure of the optically active compound (cr, + 117") was deduced * Part IX, Aust. J. Chem., 1978,31,2049. t Tentative classification; registered sample number GI 1622 (Queensland Museum, Brisbane, Qld.). Bennett, I., 'The Great Barrier Reef' p. 130 (Lansdown Press: Melbourne 1971). Benson, A. A., and Lee, R. F., Sci. Am., 1975,232, 77. Neeman, I., Fishelson, L., and Kashman, Y., Toxicon, 1974,12,593; Tursch, B., Braekman, J. C., Daloze, D., Dedeurwaerder, H., and Karlsson, R., Bull. Soc. Chim. Belg., 1978, 87, 75.