16652-64-5

60-18-4

100-44-7

16652-64-5

GENERAL STEPS: Potassium hydroxide (40.0 g, 0.605 mol) was dissolved in 100 mL of water under the cooling condition of an ice bath, L-tyrosine (50 g, 0.275 mol) was added in batches, and the temperature of the reaction system was controlled to be maintained at 15-20 °C. Copper sulfate pentahydrate (CuSO4-5H2O, 42.75 g, 0.171 mol) was then added. The reaction mixture was heated to 60-65 °C with stirring, maintained for 1 h and cooled to room temperature. N,N-dimethylformamide (DMF, 200 mL) was added to the reaction system, followed by the addition of benzyl chloride (38.12 mL, 0.33 mol) dropwise at room temperature. The reaction mixture was heated to 55 °C with stirring and kept for 2 h, during which a gray solid copper complex of O-benzyl-L-tyrosine was observed to precipitate. After the reaction mixture was cooled to room temperature, water (500 mL) was added to release the free gray solid. The solid was collected by filtration and washed with water until the filtrate was colorless. The resulting wet cake of O-benzyl-L-tyrosine copper complex was stirred with methanol (800 mL) under reflux conditions for 1 h. It was filtered, washed with methanol and dried in an oven at 65 °C. The dried copper complex was suspended in 800 mL of water, dilute hydrochloric acid was added (50 mL of hydrochloric acid dissolved in 250 mL of water), and stirred at room temperature to pH 2-3. The solid was collected by filtration, washed with 10% ammonia aqueous solution (150 mL), and finally dried in a vacuum oven at 65 °C to afford the target product O-benzyl-L-tyrosine (46.0 g, 62% yield). The melting point of the product was 259-260 °C and the mass spectrum (MS) showed m/z 294 (M+23).