LC–NMR and LC–MS identification of an impurity in a novel antifungal drug icofungipen

Successful use of LC–NMR and LC–MS for rapid identification of an impurity in a novel antifungal drug icofungipen has been demonstrated. Complementary information obtained from the two methods made it possible to determine the structure of A1 prior to its isolation and purification. Stop-flow LC–NMR (1H and DQFCOSY), LC–MS and LC–MS/MS spectra have shown that A1 is structurally related to icofungipen. It was later isolated and prepared synthetically and its structure was corroborated by high-resolution NMR spectroscopy.