Add O-[2-[[tert-butoxycarbonyl]amino]ethyl]-L-tyrosine (3.24g, 10mmol) in a 100mL three-necked flask equipped with magnetic stirring and a thermometer, with a mass concentration of 5 · 5% 21.2g of sodium carbonate aqueous solution, 20mL of 9-fluorenylmethyl-N-succinimidyl carbonate (3.37g, 10mmol) in tetrahydrofuran solution was added dropwise at room temperature, after the addition, the amidation reaction was carried out at room temperature, monitored by TLC To the end of the reaction. Concentrated to remove part of the solvent, acidified with 2N hydrochloric acid to pH 6~7, extracted with ethyl acetate, washed with saturated brine, concentrated, beaten with petroleum ether, filtered and dried to obtain a white solid O-alkyl-N-[ Fluorenylmethyloxycarbonyl]-L-tyrosine is 4.68g, the yield is 85.7%, the HPLC purity is 99.8%, and the ee value is 99.8%.
