Isolation and structure determination of a new depsipeptide crocapeptin C from the myxobacterium Melittangium boletus .

A new cyclic depsipeptide, crocapeptin C ( 1 ), containing 3-amino-6-hydroxy-2-piperidone (Ahp) was isolated from the methanol extract of the myxobacterium Melittangium boletus . The chemical structure of crocapeptin C ( 1 ) was determined through NMR and ESI-MS analysis. The stereochemistries of the constituent amino acids in crocapeptin C ( 1 ) were determined using the advanced Marfey's method and ROESY spectrum data. Crocapeptin C ( 1 ) exhibited potent inhibitory activity against chymotrypsin with an IC 50 value of 0.5 µM.