Leptosins O-S, Cytotoxic Metabolites of a Strain of Leptosphaeria Sp. Isolated from a Marine Alga

Abstract

Leptosins O (1), P (2), Q (3), R (4) and S (5) have been isolated from a strain of Leptosphaeria sp.originally separated from the marine alga Sargassum tortile.Their absolute stereostructures have been elucidated on the basis of spectroscopic analyses of their acetate derivatives (6-10) using various 1D and 2D NMR techniques and some chemical transformations.The NMR and NOE spectral analyses of 6-10 revealed that they exist in a single conformer of B type in CDCl 3 .Among these metabolites, leptosins O (1) and P (2) exhibited significant cytotoxicity against cultured P388 cells