Chemo‐enzymatic synthesis of specifically stable‐isotope labelledL‐glutamic acid and 2‐oxoglutaric acid

Abstract (3‐13C)‐, (4‐13C)‐, (5‐13C) and (3,4‐13C2)‐2‐oxoglutaric acid were prepared starting from the simple 13C‐enriched compounds: ethyl bromoacetate and paraformaldehyde, via a single reaction scheme on the gram scale in high yield. This reaction scheme allows specific 13C enrichment of every carbon position and any combination of positions. (3‐13C)‐, (4‐13C)‐, (5‐13C), (3,4‐13C2) and (15N)‐L‐glutamic acid were prepared by converting the corresponding 2‐oxoglutaric acids via an enantioselective enzymatic conversion. The labelled L‐glutamic acids and 2‐oxoglutaric acids were characterized by 1HNMR, 13CNMR and mass spectrometry.