Biosynthesis and 13C NMR assignment of cytovaricin, a neutral macrolide antibiotic

13C NMR analysis of 13C-labeled cytovaricin which was obtained by feeding sodium [1-13C]-, [2-13C]-, and [1,2-13C]acetates, [1-13C]- and [3-13C]propionates, [1-13C]isobutyrate and [methyl-13C]methionine to cultures of Streptomyces diastatochromogenes showed that the aglycone of cytovaricin is derived from nine acetate units, six propionate units and one isobutyrate unit and the methoxy group at C-3' of cymarose moiety is derived from the methionine-S-methyl group. The 13C NMR spectra of 13C-labeled cytovaricins which were obtained from feeding experiments allowed the complete assignment of the 13C NMR spectrum of cytovaricin.