76-84-6

2650-64-8

132388-60-4

Acetic anhydride (7.50 mL, 80.00 mmol) and concentrated sulfuric acid were added to glacial acetic acid (120 mL) as (S)-5-amino-2-(((benzyloxy)carbonyl)amino)-5-oxopentanoic acid (11.20 g, 40.00 mmol) and triphenylmethanol (20.80 g, 80.00 mmol). The mixture was stirred in an ice bath and then gradually warmed up to 50 °C for 2 hours of reaction. Upon completion of the reaction, the reaction mixture was slowly poured into ice (800 g) and a white precipitate precipitated. The precipitate was collected by filtration and redissolved in ethyl acetate (600 mL). The resulting solution was washed sequentially with water (3 x 200 mL), dried over anhydrous sodium sulfate, filtered and concentrated. Finally, the white solid N-Cbz-N'-trityl-L-glutamine (14.70 g, 70% yield) was obtained by solvent crystallization from ethyl acetate/petroleum ether mixture.