Proton nuclear magnetic resonance study of bleomycin in aqueous solution. Assignment of resonances

Abstract

The 1H-NMR spectrum of the glycopeptide antineoplastic antibiotic bleomycin was examined in D2O solution (Fourier transform NMR, 270 MHz) and in H2O solution (correlation nuclear magnetic resonance, 250 MHz). Resonances were assigned to specific H of the 2 most abundant congeners, bleomycin-A2 (BLM-A2) and bleomycin-B2 (BLM-B2), on the basis of homonuclear spin decoupling, comparison of the spectra of BLM-A2, BLM-B2, fragments of these antibiotics, and the related antibiotic phleomycin and pH dependence of chemical shifts. Resonance assignments are presented for all CH protons of BLM-A2 and BLM-B2 except for the saccharide groups, for which only the anomeric proton assignments are given. All of the NH protons were identified with specific resonances except for the 2 primary amide groups, which yield 4 well-resolved peaks, whose specific assignment was not attempted.