Synthesis of γ‐amino[4‐¹¹C]butyric acid (GABA)

A one‐pot synthesis of no‐carrier added γ‐amino[4‐ 11 C]butyric acid (GABA) starting with hydrogen [ 11 C]cyanide prepared from [ 11 C]carbon dioxide, is presented. Hydrogen [ 11 C]cyanide was trapped in tetrahydrofuran/potassium hydroxide in the presence of the amino polyether Kryptofix 2.2.2. A Michael addition with ethyl acrylate followed by a selective reduction and hydrolysis of the resulting amino ester gave [4‐ 11 C]GABA. The radiochemical purity of GABA was higher than 99% and the decay corrected radiochemical yield was 60–65% based on the amount of H[ 11 C]CN used. The total synthesis time including purification was around 40 min, counted from the start of the Michael addition reaction.