Tao Guoliang from the Department of Chemistry of Wuhan University and others have given the following synthetic route: Preparation of I 0.5mmol of benzyloxycarbonyl aspartic acid, 1.5mmol of phenylalanine methyl ester hydrochloride and 2.5mL of water were added to 25mL of cone The pH value was adjusted to 6 with ammonia water, 7 mg of thermophilic protease was added, and the reaction was stirred at 40 °C for 6 h. Filter, wash with distilled water, and dry to obtain 0.29 g of white solid (I), yield 95.6%, melting point 116-118°C. Elemental analysis results: C62.96%, H6.09%. N6.65%.
(2) Preparation of II Add 0.5 g of sample I and 20 mL of 3 mol/L hydrochloric acid to a 25 mL conical flask, and stir and react at 45°C for 0.5 h. Filter, wash with distilled water, and dry to obtain 0.32 g of product II, with a yield of 92% and a melting point of 129-131 °C. Elemental analysis results: C61.45%, H5.42%, N6.82%. Preparation of III 0.2 g of palladium-carbon (10%) catalyst, 20 mL of glacial acetic acid and 5 mL of water were added to a 100 mL three-necked flask, and hydrogenated for activation for 1.5 h. 20 mL of glacial acetic acid dissolved in 0.6 g II was added, and the mixture was stirred and hydrogenated at 30 °C for 6 h. After completion of the reaction, filter and wash the catalyst with glacial acetic acid three times; the filtrate and washings were concentrated to dryness under reduced pressure, 15 mL of benzene was added, and 15 mL of benzene was added, and concentrated to dryness under reduced pressure to obtain a white solid, which was dried to obtain product III, 0.38 g, with a yield of 92.3%. , the melting point of 245 ℃. Elemental analysis results: C55.63%, H6.23%, N8.96%.