Secondary metabolites from the cnidarian Cavernularia sp.: structures of the new briaranes cavernulin A and B

Novel cyclized cembranoids (briaranes) cavernulin A and cavernulin B along with ubiquitous wax esters (derived from saturated fatty acids and some analogous unsaturated fatty acids), cholesterol, ceramides as well as 1-O-alkylglycerols have been isolated from the cnidarian Cavernularia sp., the extract of which shows some toxicity to guppy fingerlings and in brine-shrimp assays. The structures of cavernulia A as (1S * ,2S * ,5Z,7S * ,8R * ,9S * ,10S * ,11R * ,12R * ,17R * )-2,9-diacetoxy-12-butanoyloxy-8-hydroxybriara-5,13-dien-18-one and cavernulin B as (1S * ,2S * ,5Z,7S * ,8R * ,9S * ,10S * ,11R * ,12R * ,17R * )-2,9-diacetoxy-8,12-dihydroxybriara-5,13-dien-18-one are established from one-dimensional [ 1 H and homodecoupling as well as 1 3 C (NDC and DEPT-135)] and two-dimensional (COSY-90, X-II correlation optimized for 1 J C - H and NOESY) NMR and other (IR and Mass) spectral and some chemical studies. The lengths of the alkyl chains in wax esters, ceramides and 1-O-alkylglycerols are established by appropriate gas chromatographic studies.