GENERAL STEPS: 18.73 g (0.11 mol) of sodium glutamate and 75 g of water were added to the reaction vessel, adjusted to pH=8 using 1 mol/L aqueous sodium hydroxide solution, and mixed with stirring. Subsequently, 28.31 g of dichloroethane solution of 4-nitrobenzoyl chloride prepared in step (1) was slowly added dropwise to the reaction system at 0 °C. During the dropwise addition, the pH of the reaction system was adjusted with 1 mol/L aqueous sodium hydroxide solution, maintaining pH=8. The color of the reaction solution gradually changed from white to purple, indicating that the reaction proceeded. The reaction was continued for 1 h at room temperature to ensure the completion of the reaction. After completion of the reaction, electrostatic layered separation was carried out and the organic layer was extracted twice with water. The combined aqueous layers were acidified by adjusting to PH=1 with hydrochloric acid, and the precipitated crystals were filtered and dried to afford N-p-nitrobenzoylglutamic acid 29.81 g. The purity of the product was 98.43% by HPLC, and the yield was 99.03% (based on 4-nitrobenzoyl chloride).
