Sulfoureido Lipopeptides from the Marine Sponge Discodermia kiiensis

New N-sulfoureidylated lipopeptides, sulfolipodiscamides A-C (1-3), were isolated by gel filtration chromatography of the n-butanol fraction of the marine sponge Discodermia kiiensis. By extensive NMR analyses and high-resolution mass spectrometry, the structures of 1-3 were elucidated as having an unprecedented N-sulfoureidyl group on the d-citrulline residue, a distinct feature that was not found in the structurally related lipodiscamides A-C (4-6), derived from the ether fraction of the same sponge. Furthermore, the absolute configurations of 1-3 were confirmed by comparisons of the HPLC retention times of the hydrolytic products and the corresponding authentic lipodiscamides. Interestingly, sulfolipodiscamide A displayed a 2.3-fold increase in cytotoxicity against murine leukemia (P388) cells, compared to the unconjugated parent compound.