Synthesis of ¹¹C-methionine through gas phase iodination using Synthra MeI_Plus synthesis module

A method of ¹¹C-methionine synthesis using ‘bubbling’ method is presented. ¹¹C-methionine was synthesized via ¹¹C methylation from L-cysteine thiolactone (2 mg) in a 300 μL solution of 2:1:1 (v/v) 1 M NaOH, ethanol, and water at ambient temperature (85°C, 5 min). The radiochemical purity of radiotracer was higher than 99% and enantiomeric purity (L-¹¹C-methionine) was 91.6 ± 0.4%. The final product met the requirements of European Pharmacopoeia monograph. The proposed ¹¹C-methionine synthesis is a reliable tool for routine manufacturing in clinical applications and animal studies.