Berninamycins B, C, and D, minor metabolites from Streptomyces bernensis

Berninamycins B, C, and D were isolated from fermentation of Streptomyces bernensis and their structures were studied with 13C NMR and FAB mass spectrometry. Berninamycin B has a valine unit in its cyclic peptide loop instead of the beta-hydroxyvaline unit found in berninamycin A. Berninamycin D has two fewer dehydroalanine units attached to the carboxyl carbon of the pyridine ring. Based on FAB-MS results, berninamycin C is postulated to have only one dehydroalanine unit attached to the carboxyl carbon of pyridine. The biogenesis of berninamycins B, C, and D is discussed.