Synthesis of Tritiated Glutamic Acid and Pyroglutamate

Abstract

It was shown that introduction of tritium directly into glutamic acid does not afford a highly labeled product (at 160°C, a specimen with a specific radioactivity of 3–5 Ci/mmol was formed; at 180°C, the specific radioactivity was 26 Ci/mmol; and at 200°C, the compound strongly degraded). Heating a mixture of 5% Pd/Al₂O₃ with alumina-supported sodium glutamate at 220°C for 7.5 min gave mainly [³H]pyroglutamate. After isolation and purification of [³H]pyroglutamate, its solution in 1 N HCl was heated at 105°C for 20 h. This yielded [³H]glutamic acid with a specific radioactivity of 40 Ci/mmol.