Isolation, identification and characterization of related substances in furbenicillin.

Furbenicillin is a broad-spectrum semisynthetic penicillin with strong antibacterial activity against Gram-negative bacteria. In this study, three impurities in furbenicillin, including an unknown epimer, were determined. On the basis of a complete analysis of the spectrum (MS, (1)H,(13)C, 2D NMR and CD) and the results of chemical methods, the unknown epimer impurity was identified as 10-epi-furbenicillin (impurity 1). Isolation and structure elucidation of impurity 1 was also reported here for the first time.