The general procedure for the synthesis of DL-2-aminobutyric acid methyl ester hydrochloride from methanol and Boc-L-2-aminobutyric acid was as follows: 10.0 g (49.2 mmol) of Boc-L-2-aminobutyric acid was dissolved in 100 mL of methanol, and 6 mL (82.2 mmol) of thionyl chloride was added slowly and dropwise at 0 °C. The reaction mixture was stirred at room temperature for 14 hours. Upon completion of the reaction, the solvent was removed by vacuum evaporation to obtain the crude product. The crude product was further processed to obtain 7.6 g (101% yield) of DL-2-aminobutyric acid methyl ester hydrochloride. The product was analyzed by electrospray mass spectrometry (ES-MS), showing the (M + H)+ peak located at m/z 118.
