Hydrochloric Acid → Benzyl 2-amino-2-methylpropanoate hydrochloride

To a solution of 2-(tert-butoxycarbonylamino)-2-methylpropionic acid (4.06 g) in N,N-dimethylformamide (40 mL) were added potassium carbonate (4.15 g) and benzyl bromide (2.85 mL), and the mixture was stirred at room temperature for 2 hours. The reaction mixture was poured into water, and the resulting mixture was extracted with ethylacetate. The extract was washed with water and brine, and dried over anhydrous sodium sulfate. The solvent was removed under reduced pressure. The residue (solid) was treated with n-hexane and collected by filtration. The crystals were dried under reduced pressure to give benzyl 2-(tert-butoxycarbonylamino)-2-methylpropionate (4.44 g). To the obtained benzyl 2-(tert-butoxycarbonylamino)-2-methylpropionate (4.44 g) was added 4 mol/L hydrochloric acid (1,4-dioxane solution, 15 mL), and the mixture was stirred at room temperature overnight. The reaction mixture was diluted with diethyl ether, and the mixture was stirred for 1 hour. The insoluble material was collected by filtration, washed with diethyl ether and dried under reduced pressure to give the title compound (3.4 g).