Incorporation of carboxyl and methyl carbon-13 labeled acetates into racemomycin A by Streptomyces lavendulae ISP 5069.

Sir: In a previous study of biosynthetic pathways leading to the formation of racemomycin A, we observed that 14C from (U-14C)arginine was not located in the streptolidine moiety in this antibiotic, whereas the 14C from (1-14C)acetate was. However, we did not determine the distribution of labeled atoms in the metabolite. The availability of CMR spectroscopy prompted us to use 13C-labeled acetate for this purpose . Acetate was incorporated into racemomycin A as follows: Submerged cultures of Streptomyces lavendulae ISP 5069 were grown at 27°C on a reciprocal shaker (160 rpm) in an organic medium as described before.2) In the first experiment, racemomycin A was labeled with sodium (1-13C)acetate, and in the second with sodium (2-13C)acetate (Merck Sharp and Dohme, Canada, 90 atom % 13C), by adding an aqueous solution (I ml containing 100 mg of acetate) to 100 ml of the broth after 4 hours and again after 68 hours of cultivation. Production of the antibiotic was depressed approximately 25 under these conditions. Racemomycin A was isolated by column chromatography on Amberlite IRC-50(Na+), then on activated carbon3) and several times on Sephadex LH-204). Homogeneity of the antibiotic was examined by chromatography on Toyo-Roshi No. 51 paper with BuOH-pyridineAcOHH2Otert.-BuOH(15 :10 :