Lyngbyastatin 4, a dolastatin 13 analogue with elastase and chymotrypsin inhibitory activity from the marine cyanobacterium Lyngbya confervoides.

Lyngbyastatin 4 (1), a new depsipeptide containing the unusual amino acid homotyrosine and a 3-amino-6-hydroxy-2-piperidone (Ahp) residue, was isolated from a collection of the marine cyanobacterium Lyngbya confervoides off the Florida Atlantic coast. Its gross structure was determined by NMR spectroscopy, and the configurations of asymmetric centers were assigned after chiral HPLC analysis of hydrolysis products. Lyngbyastatin 4 (1) is an analogue of the sea hare isolate dolastatin 13 and several marine cyanobacterial metabolites, further supporting the notion that many of the dolastatins are of cyanobacterial origin. Lyngbyastatin 4 (1) selectively inhibits elastase and chymotrypsin in vitro over other serine proteases with IC50 values of 0.03 and 0.30 microM, respectively.