ENZYMATIC-SYNTHESIS OF SPECIFICALLY H-2-LABELED L-GLUTAMIC ACIDS AND H-2-LABELED, N-15-LABELED, C-13-LABELED L-GLUTAMINES ON A PREPARATIVE-SCALE

In this paper we report the preparation of specifically H-2-labelled L-glutamic acids and H-2-, N-15-, C-13-labelled L-glutamines on the gram scale. The products obtained have high isotope enrichment (>98%) and high optical purity. The synthetic schemes allow the specific isotope enrichment of every H, C, and N position or any combination of positions. (2-H-2)-L-Glutamic acid was synthesized by enantioselective enzymatic conversion of 2-oxoglutaric acid using glutamate dehydrogenase (GDH, E.C. 1.4.1.3.), alcohol dehydrogenase (ADH, E.C. 1.1.1.1.) and (H-2(6))ethanol. (3,3-H-2(2))-L-Glutamic acid was prepared by enzymatic conversion of 2-oxo-3,3-di-deuteroglutaric acid which was easily obtained from 2-oxoglutaric acid by isotope exchange reaction in (H2O)-H-2 at pH 13.0 (4,4-H-2(2))-L-Glutamic acid was obtained by chemical exchange in 20% HCl. Four different isotopomers of L-glutamine [(2-H-2)-, (3,3-H-2(2))-, and (5-C-13)-L-Gln] were synthesized by the enantioselective conversion of isotopically labelled L-glutamic acids using glutamine synthetase (GS, E.C. 6.3.1.2.). The amide group of glutamine was labelled with N-15 using (NH4Cl)-N-15 in the enzymatic reaction. The labelled L-glutamic acids and L-glutamines were characterized by H-1-NMR, C-13-NMR and mass spectrometry.