A chemical study of cyclic depsipeptides produced by a sponge-derived fungus.

Two novel cyclic depsipeptides, guangomides A (1) and B (2), together with a new destruxin derivative (3) were isolated from the cytotoxic extract obtained from the saltwater culture of an unidentifiable sponge-derived fungus. The new structures were elucidated on the basis of analysis of extensive 1D and 2D NMR data sets, and the absolute configurations of 2S, 9S, 13S, 19S, 24R, 28R of 1 were determined on the basis of the combined X-ray and Marfey's method structure analysis. Identical absolute configurations were assumed for 2. The cytotoxicity of the extract was found to be due to brefeldin A, while 1 and 2 showed weak antibacterial activity against Staphylococcus epidermidis and Enterococcus durans.