反应详情

Acetyl chloride (61 mL, 860 mmol) was added dropwise to 200 mL of MeOH at 0° C. The mixture was stirred at room temperature for 30 min, and 22.5 g (124 mmol) of 2-amino-4-bromo-butyric acid hydrobromide was added. The mixture was stirred overnight and concentrated. The residue was washed with Et2O to provide 23.5 g (82%) of methyl 4-bromo-2-amino-butyrate hydrochloride. A solution of 27.7 g (330 mmol) of NaHCO3 in 100 mL of water was slowly added to 19.2 g (82.5 mmol) of this material along with 21.6 g (99.0 mmol) of Boc2O in 140 mL of 1,4-dioxane at 0° C., The mixture was warmed to room temperature and stirred overnight. N,N-dimethylpropane-1,3-diamine (5 mL) was added to the mixture, and stirring was continued for 20 min. The mixture was diluted with water then extracted twice with EtOAc. The extracts were washed with water, 1M NaHSO4, and brine, and then combined, dried with Na2SO4, filtered, and concentrated to provide 21.5 g (88%) of 4-bromo-2-tert-butoxycarbonylamino-butyric acid methyl ester as a white solid.

1. stirringThe mixture was stirred overnight
2. concentrationconcentrated
3. washThe residue was washed with Et2O