To a 500 mL four-necked flask equipped with a mechanical stirrer, a thermometer and a reflux condenser tube (connected to a 30% aqueous sodium hydroxide solution absorption unit) were sequentially added 280 g of benzyl alcohol, 14.7 g (0.10 mol) of L-glutamic acid and 30.0 g (0.25 mol) of thionyl chloride. The reaction mixture was heated to 80-85 °C and the reaction was stirred at this temperature for 5 hours. Upon completion of the reaction, the reaction solution was cooled to 20-25 °C and nitrogen was passed to displace the hydrogen chloride gas in the system for 30 min. Subsequently, excess thionyl chloride and benzyl alcohol were recovered by distillation. To the residue, 120 mL of methyl tert-butyl ether was added for pulping treatment, and the solid product was collected by filtration and dried to give 35.9 g of white solid L-glutamic acid dibenzyl ester hydrochloride, which was analyzed by liquid chromatography to have a purity of 99.8% and a yield of 98.7%.
[1] Patent: CN107602436, 2018, A. Location in patent: Paragraph 0047; 0048; 0049; 0050
[2] Journal of the Chinese Chemical Society, 2009, vol. 56, # 5, p. 1010 - 1017
[3] Bioorganic and Medicinal Chemistry, 2010, vol. 18, # 17, p. 6220 - 6229
