New cyclic depsipeptides from the green alga Bryopsis species; application of a carboxypeptidase hydrolysis reaction to the structure determination

New cyclic depsipeptides, kahalalides P () and Q (), were isolated from the Hawaiian green alga Bryopsis sp. The sequential positions of the dl anti-podal amino acids were determined by a carboxypeptidase hydrolysis reaction. This enzymatic method will be applicable to the structure determination of other non-ribosomal peptides. The absolute chemistry of 3-hydroxy-9-methyldecanoic acid in kahalalides P and Q were determined by the recently introduced convenient Mosher ester procedure.