25024-53-7

Figure 1

Experimental Procedure:

2,4-Dinitrophenyl-L-histidine was dissolved in 100 mL of sodium hydroxide aqueous solution. 200 mL of tetrahydrofuran and 250 g of di-tert-butyl dicarbonate were added sequentially. The pH was controlled at 8-9. After reacting for 12 h, the mixture was extracted twice with 500 mL of ethyl acetate each time. The aqueous phase was then acidified with HCl to pH 1-2, and the product was extracted three times with 500 mL of ethyl acetate each time. The ester layers were combined and washed twice with 200 mL of saturated brine each time. The mixture was dried over anhydrous sodium sulfate for 12 h, filtered, concentrated, crystallized, and dried at 40-50 °C to obtain BOC-HIS(DNP)-OH.