A 13C NMR study of actinomycin D and related model peptides

¹³C n.m.r. pulsed Fourier transform spectra were measured and interpreted for actinomycin D and for two related peptide derivatives: BOC-Pro-Sar-OCH₃ and BOC-Sar-Meval-OCH₃. Actinomycin D, specifically enriched with ¹³C in the chromophoric C-methyl and in the peptide N-methyl carbons, was produced biosynthetically. Enrichment of specific N-methyl carbons in the model peptides was effected synthetically. Spectral assignments relied on the use of the enriched samples and particularly on off-resonance and selective low power ¹H decoupling experiments. Poor correlation was observed between some of the ¹³C chemical shifts in the model compounds and those of the analogous carbons in actinomycin D. Ten of our ¹³C assignments for actinomycin D differ from those published by Hollstein, Breitmaier and Jung.