Abstract: A series of labeled a-arginines have been fed to fermentations of Streptomyces griseochromogenes in order to examine the mechanism of L-@-arginine formation in the biosynthesis of the antibiotic blasticidin S.[3-'3C, 2-'SN] Arginine was synthesized and fed; analysis of the derived antibiotic by I3C NMR spectroscopy revealed the retention of the original a-nitrogen and its intramolecular migration to the@ position, revealing the ...