Nostocyclamide M:: a cyanobacterial cyclic peptide with allelopathic activity from Nostoc 31

A cyclic peptide containing thiazole and oxazole moieties was isolated from Nostoc 31 and its structure determined by chemical degradation detailed NMR and mass: spectroscopic analyses. The compound is stereochemically pure and closely related to nosto-cyclamide in which D-valine is replaced by D-methionine. Therefore. it differs from tenuecyclamide C reported to contain L methionine. It shows allelopathic activity against Anabaena 7120, but is inactive against grazers. (C) 2001 Elsevier Science Ltd. All rights reserved.