The use of D<sub>2</sub> and deuterium water for the introduction of a label into 4-aminobutanoic acid

The efficiency of incorporating deuterium into 4-aminobutanoic acid (GABA) has been studied. When using D2O at 200°C, about 0.5 deuterium atom was included in GABA on average. When using D2O with trifluoroacetic acid (1 : 1) at 250°C, an average of 1.49 deuterium atoms with a yield of 15% were included. When using the solid-phase method, it was possible to introduce about 3 deuterium atoms per GABA molecule. During isotopic exchange with D2O, the use of a palladium–rhodium mixture pretreated with gaseous deuterium made it possible to obtain [D]GABA with the deuterium content of 4.5–4.6 atoms. But in both cases, the yields of [D]GABA were low. Preparative amounts of [D]GABA were obtained using additional carriers. The best result was obtained when applying GABA to zeolite. Using D2O and 5% Pd/BaSO4–GABA–zeolite pretreated with deuterium gas, [D]GABA was obtained with an average content of 1.5–2.0 deuterium atoms and a yield of about 30%.