Structural characterization of daptomycin analogues A21978C1-3(d-Asn11) produced by a recombinant Streptomyces roseosporus strain.

Three daptomycin-related lipopeptides, A21978C1-3(d-Asn11) (2−4), were purified from the fermentation broth of a recombinant Streptomyces roseosporus strain. Their chemical structures were determined by analyses of the biosynthetic pathway, chemical transformations, d,l-amino acid quantitation by enantiomer labeling, tandem LC-MS/MS, and 2D-NMR techniques. Compounds 2−4 exhibited potent antibacterial activity against Staphylococcus aureus with MIC values of 0.6, 0.3, and 0.15 μM, respectively, well correlated to the acyl tail chain length.