The Use of D₂ and Deuterated Water for the Introduction of a Label into 4-Aminobutanoic Acid

The efficiency of incorporating deuterium into 4-aminobutanoic acid (GABA) has been studied. The use of D₂O at 200°C makes it possible to introduce into GABA an average of about 0.5 deuterium atoms, D₂O with trifluoroacetic acid (1 : 1) at 250°C, an average 1.49 deuterium atoms with a yield of 15%. The solid-phase method permits introducing about 3 deuterium atoms per GABA molecule. During isotopic exchange with D₂O, the use of a palladium–rhodium mixture pretreated with deuterium gas made it possible to produce [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 produced engaging additional supports. The best result was obtained when applying GABA to zeolite. Using D₂O with 5% Pd/BaSO₄–GABA–zeolite pretreated with deuterium gas, allows producing [D]GABA with an average content of 1.5–2.0 deuterium atoms and a yield of about 30%.