Synthesis of N-acetyl-l-aspartyl-l-glutamic acid; [³ H]NAAG

[³ H]NAAG, N-acetyl-l-aspartyl-l-glutamic acid, has been widely used as a substrate in glutamate carboxypeptidase II (GCPII) reactions, either to determine the inhibitory constants at 50% inhibition (IC₅₀ ) of novel compounds or to measure GCPII activities in different tissues harvested from various disease models. The importance of [³ H]NAAG, combined with its current commercial unavailability, prompted the development of a reliable eight-step synthetic procedure towards [³ H₂ ]NAAG starting from commercially available pyroglutamate. Pure [³ H]NAAG of high molar activity (49.8 Ci/mmol) and desired stereochemistry was isolated in high radiochemical yield (67 mCi) and radiochemical purity (>99%). The identity was confirmed by mass spectrometry and co-injection with unlabeled reference.