Cavomycins A-C, Linear Oligomer Depsipeptides from an Annelid-Associated Streptomyces cavourensis .

Three unique linear oligomeric depsipeptides, designated as cavomycins A-C ( 1 - 3 ), were identified from Streptomyces cavourensis , a gut bacterium associated with the annelid Paraleonnates uschakovi . The structures of these depsipeptides were determined through a combination of spectroscopic methods and chemical derivatization techniques, including methanolysis, the modified Mosher's method, advanced Marfey's methods, and phenylglycine methyl ester derivatization. The unique dipeptidyl residue arrangements in compounds 1 - 3 indicate that they are not degradation products of valinomycin. Compound 2 and its methylation derivative 2a exhibited antiproliferative activity against PANC-1 pancreatic cancer cells with IC 50 values of 1.2 and 1.7 μM, respectively.