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

13 C n.m.r. pulsed Fourier transform spectra were measured and interpreted for actinomycin D and for two related peptide derivatives: BOC‐Pro‐Sar‐OCH 3 and BOC‐Sar‐Meval‐OCH 3 . Actinomycin D, specifically enriched with 13 C 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 1 H decoupling experiments. Poor correlation was observed between some of the 13 C chemical shifts in the model compounds and those of the analogous carbons in actinomycin D. Ten of our 13 C assignments for actinomycin D differ from those published by Hollstein, Breitmaier and Jung.