Example 44A: 300 mg (1.02 mmol) of (S)-3-benzyloxy-2-tert-butoxycarbonylamino-propionic acid was dissolved in 10 mL of dichloromethane (DCM) at 0 °C and 1.5 mL (20.5 mmol) of thionyl chloride was added slowly. The reaction mixture was stirred at 0°C for 14 hours. Upon completion of the reaction, the mixture was concentrated, followed by addition of methanol and evaporation several times to give O-benzyl-L-serine methyl ester hydrochloride as a white solid. Yield: 270 mg (100%).LC-MS (Method 1s): retention time (RT) = 0.92 min, MS (ESI pos): m/z = 210 (M + H)+.
