Total structure and biological properties of laxaphycins A and B,cyclic lipopeptides from the marine cyanobacterium Lyngbya majuscula

Summary The tropical marine cyanobacteriumLyngbya majuscula produces a series of cytotoxic and antimicrobial cyclic peptides. The total structure of the two major components, laxaphycins A and B, was determined by interpretation of physical data, principally high field NMR, FAB MS and MS/MS, in combination with chemical derivatization and degradation schemes. Absolute stereochemistries of the natural and ‘exotic’ amino acids were determined. The two cyclic peptides exhibited an unusual biological synergism when tested for antifungal or cytotoxic effects.