LEPTOSINS, ANTITUMOR METABOLITES OF A FUNGUS ISOLATED FROM A MARINE ALGA

Leptosins A B, C, D, E and F, chaetocin derivatives, have been isolate d from the mycelium of a strain of Leptosphaeria so. attached to the m arine alga Sargassum tortile. Their stereostructures, with a different configuration from that of related compounds, have been elucidated by spectroscopic analyses using various 1D and 2D NMR techniques and som e chemical transformations. All the compounds showed potent cytotoxici ty against cultured P388 cells, and leptosins A and C exhibited signif icant antitumour activity against Sarcoma 180 ascites.