Asmarines G and H and barekol, three new compounds from the marine sponge Raspailia sp

Four asmarines, the known A and F and two new ones G and H, four diterpenes, the known chelodane, barekoxide, and zaatirin and a new one, barekol, and methyl 3-oxo-cholan-24-oate were isolated from the Kenyan sponge Raspailia sp. The structures of all these compounds were established on the basis of MS and NMR data, and the absolute configuration of barekol was determined from the CD measurements of its keto-derivative. The (15)N chemical shifts of the N atoms of the heterocycles of the asmarines were measured from (15)N HMBC experiments, and the influence of various structural features on the delta(N) values studied.