D-Valine, 20 mL of ethyl acetate and 10 mL of tetrahydrofuran were added to the reaction bottle, 4.2 g (19.3 mmol) of Boc anhydride was added to the reaction system, and stirred at room temperature for 6 h. The progress of the reaction was detected by thin-layer chromatography, and waited for the end of the reaction. The reaction solution was evaporated to dryness, and saturated ammonium chloride solution was added to the residual solution to separate the organic phase, which was then washed with saturated saline, dried, filtered and evaporated to dryness to obtain Boc-D-valine.
