The general procedure for the synthesis of Boc-L-aniline-4-nitrophenyl ester from 4-nitrophenol and Boc-L-phenylalanine is as follows: dissolve N-tert-butoxycarbonyl-L-phenylalanine (50 g) in dichloromethane (800 ml), stirring until completely dissolved. P-nitrophenol (39 g), 4-dimethylaminopyridine (DMAP, 3 g) and dicyclohexylcarbodiimide (DCC, 39 g) were added and the reaction was carried out for 5 hours at about 20°C. After completion of the reaction, the reaction mixture was filtered and the filtrate was evaporated. Ethanol was added to the residue and heated until complete dissolution, then slowly cooled to 20-30°C to allow the solid to precipitate gradually. Water (50 ml) was added and the mixture was cooled to 0°C and crystallized for 1 hour. The solid was collected by filtration to afford the target product Boc-L-aniline-4-nitrophenyl ester (62 g, 86.5% yield, 93% purity).
