General procedure for the synthesis of L-glutamic acid bisbenzyl ester p-toluenesulfonate from L-glutamic acid, 4-methylphenylsulfonic acid and benzyl alcohol: 29.4 g (0.2 mol) of L-(+)-glutamic acid, 40 g (0.23 mol) of p-toluenesulfonic acid and 80 mL of benzyl alcohol were dissolved in 500 mL of toluene. 11 mL of water was separated by refluxing under nitrogen protection. Refluxing was continued for 3 hours, followed by evaporation and removal of 150 mL of liquid. The reaction solution was cooled to 50°C and then poured into a beaker containing 600 mL of petroleum ether and stirred for 1 hour. The precipitate was collected by filtration. The filter cake was dissolved in 280 mL of 95% ethanol by heating, and after the heating was stopped, the solution was cooled overnight. The precipitate was collected by filtration and dried under vacuum to give 61 g of L-(+)-glutamic acid bisbenzyl ester p-toluenesulfonate (Compound 1).
