Carbon-13 NMR spectra of rifamycins

The natural abundance ¹³C Fourier transform magnetic resonance spectra of rifamycin S and some of its derivatives have been studied. A combination of five different approaches has made unambiguous assignments for most of the resonances possible: (1) comparative study of the non- decoupled and noise-decoupled spectra; (2) ¹³C spectral characteristics; (3) spectral comparison between derivatives; (4) selective proton decoupling; (5) biogenetic evidence. Pulse and Fourier transform ¹³C NMR spectroscopy provides a more complete picture of these complex molecules than was previously obtained by ¹H NMR spectroscopy.