To a solution of 9.82 g (0.041 mol) tert-butyl L-tyrosinate in 150 mL of dichloromethane and 20 mL of DMF was added 5.2 g (0.04 mol) of triethylamine, followed by 9.03 g (0.04 mol) of di-tert-butyl dicarbonate. The reaction mixture was stirred at room temperature for 2 h. Upon completion of the reaction, it was washed sequentially with 1N HCl (3 × 50 mL), saturated NaHCO3 solution (1 × 50 mL), and brine (1 × 50 mL). The organic phase was dried with anhydrous magnesium sulfate, filtered and concentrated in vacuum to give 13.59 g (98% yield) of white solid product. The structure of the product was confirmed by 300 MHz 1H NMR (CDCl3): δ 1.42 (s, 18H), 2.95 (d, 2H), 4.39 (dd, 1H), 5.01 (d, 1H), 6.15 (s, 1H), 6.70 (d, 2H), 7.00 (d, 2H).
