Biosynthesis of the Lincomycins. 1. Studies Using Stable Isotopes on the Biosynthesis of the Propyl- and Ethyl-L-hygric Acid Moieties of Lincomycins A and B

The biosynthesis of the propyl-L-hygric acid and ethyl-L-hygric acid moieties of lincomycins A and B has been examined by using deuterated and carbon-13 labeled precursors in combination with carbon-13 NMR and mass spectral analysis. The results, using specifically deuterated tyrosine, DOPA, and methionine, demonstrate that tyrosine is converted via DOPA to an intermediate that undergoes aromatic ring cleavage most probably via a 2,3-extradiol cleavage reaction. An experiment using D-(¹³C₆)glucose in combination with analysis of the ¹³C-¹³C spin-coupling patterns in lincomycin A and propyl-L-hygric acid permits the determination of those carbon atoms that remain together during the biosynthesis of lincomycin A. Glucose is converted via glycolysis and the hexose monophosphate shunt to phosphoenolpyruvate and erythrose 4-phosphate, respectively, which are in turn converted via the shikimic acid pathway to tyrosine and hence into DOPA. The subsequent reactions after DOPA are consistent with the 2,3-extradiol cleavage pathway and an addition of a C-1 unit from methionine to give rise to the terminal methyl group of the propyl side chain. These results are now consistent with those obtained for the C₂- and C₃-proline moieties found in anthramycin, tomaymycin, and sibiromycin that are also biosynthetically derived from tyrosine.