Methyl 4-(tert-butoxycarbonyl)morpholine-2-carboxylate (251 mg, 1.02 mmol) was used as a raw material and dissolved in methanol (15 mL). To this solution was added 1 mol/L aqueous potassium hydroxide solution (3 mL). The reaction mixture was stirred at room temperature for 8 hours. Upon completion of the reaction, water was added to the mixture and the pH was adjusted with 5% aqueous citric acid solution. subsequently, the reaction mixture was extracted with ethyl acetate. The organic phase was washed with saturated brine and dried with anhydrous magnesium sulfate. The solvent was evaporated under reduced pressure to give 219 mg (93% yield) of the target product 4-Boc-2-morpholinecarboxylic acid as a colorless powder. The product was characterized by 1H NMR (400 MHz, DMSO-d6): δ1.40 (9H, s), 2.70 (1H, dd, J=41.6,15.3 Hz), 3.03-3.09 (1H, m), 3.43-3.54 (2H, m), 3.78 (1H, m), 3.85 (1H, dt, J=11.6,3.7 Hz), 4.04 (1H, dd, J=8.6,3.7Hz), 12.73 (1H, brs).
