Leptosins, antitumour metabolites of a fungus isolated from a marine alga

Abstract

Leptosins A B, C, D, E and F, chaetocin derivatives, have been isolated from the mycelium of a strain of Leptosphaeria sp. attached to the marine 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 some chemical transformations. All the compounds showed potent cytotoxicity against cultured P388 cells, and leptosins A and C exhibited significant antitumour activity against Sarcoma 180 ascites.