Enzymatic synthesis of specifically 2H‐labelled L‐glutamic acids and 2H‐, 15N‐, 13C‐labelled L‐glutamines on a preparative scale

Abstract

AbstractIn this paper we report the preparation of specifically 2H‐labelled L‐glutamic acids and 2H‐, 15N‐, 13C‐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. (2‐2H)‐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 (2H6)ethanol. (3,3‐2H2)‐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 an isotope exchange reaction in 2H2O at pH 13.0. (4,4‐2H2)‐L‐Glutamic acid was obtained by chemical exchange in 20% 2HCl. Four different isotopomers of L‐glutamine [(2‐2H)‐, (3,3‐2H2)‐, (4,4‐2H2)‐, and (5‐13C)‐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 15N using 15NH4Cl in the enzymatic reaction. The labelled L‐glutamic acids and L‐glutamines were characterized by 1H‐NMR, 13C‐NMR and mass spectrometry.