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 h before the solvent was removed by vacuum evaporation. Finally, 7.6 g (101% yield) of DL-2-aminobutyric acid methyl ester hydrochloride was obtained, whose mass spectrometry analysis showed that the (M + H)+ peak was located at 118 m/z.
