Stereochemical analysis and cytotoxicity of kulokekahilide-2 and its analogues

We report the conformational analysis of kulokekahilide-2, a cytotoxic cyclic depsipeptide, and its analogues. We also evaluated their cytotoxicity against human cancer cells. Although both the cis and trans conformations are possible for the amide bond between MePhe and MeGly, only one conformation was observed in DMSO. We also reveal that the configuration at C-43 in kulokekahilide-2 controls intramolecular ester exchange between the 26- and 24-membered cyclic depsipeptides. Kulokekahilide-2 and its analogues were evaluated for their cell-growth inhibition profile and using COMPARE analysis, which suggested a mechanism of action different from that of standard anticancer drugs.