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 IC50 value of 0.5 µM.