Sokodosides, steroid glycosides with an isopropyl side chain, from the marine sponge Erylus placenta

Two novel steroid glycosides, sokodosides A and B (1 and 2, respectively), were isolated from the marine sponge Erylus placenta as growth-inhibitory principles against several strains of yeast and a cancer cell line. Sokodosides possess the novel carbon skeleton as characterized by the presence of a combination of isopropyl side chain and the 4,4-dimethyl steroid nucleus. Sokodoside B has another unique characteristic in the presence of delta(8,14,16) unsaturation. The structures of sokodosides were determined by analysis of spectral data and chemical degradation. The absolute stereochemistry of sokodoside A (1) was determined by the application of the modified Mosher analysis to the aglycon obtained by acid hydrolysis, whereas the absolute stereochemistry of the monosaccharide units in 1 and 2 was determined by chiral GC analyses of the acid hydrolysates.