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A previously unreported heterodetic cyclic peptide, homophymamide A (1), was isolated from a Homophymia sp. marine sponge. The structure of homophymamide A was determined to be a lower homologue of anabaenopeptins by spectroscopic analysis, chemical degradation, and chemical synthesis. Analysis of the acidic hydrolysate showed that the racemization of Lys took place, leading us to pose a cautionary note on the configurational assignment of peptides that contain a ureido bond.

A previously unreported heterodetic cyclic peptide, homophymamide A (

We have discovered new glycosylated fatty acid amides, stellettosides, from a Stelletta sp. marine sponge. They were detected through LC-MS analysis of the extract combined with the cytotoxicity assay of the prefractionated sample. Their planar structures were determined by analyses of the NMR and tandem FABMS data. Stellettosides A1 and A2 (1 and 2) as well as stellettosides B1-B4 (3-6) were obtained as inseparable mixtures. Careful analysis of the NMR and tandem FABMS data of each mixture, along with comparison of the tandem FABMS data with that of a synthetic model compound, permitted us to assign the structure of the constituents in the mixture. The absolute configuration of the monosaccharide unit was determined by LC-MS after chiral derivatization. The relative configurations of the vicinal oxygenated methines in the fatty acid chains were assigned by the (1)H NMR data of the isopropylidene derivative. The mixture of stellettosides B1-B4 (3-6) exhibit moderate cytotoxic activity against HeLa cells with an IC50 value of 9 μM, whereas the mixture of stellettosides A1 and A2 (1 and 2) was not active at a concentration of 10 μM.