1. 5.4 mL of thionyl chloride (about two drops) was slowly added dropwise to a 100 mL three-necked flask containing 40 mL of ethanol under an ice-water bath and mechanical stirring, and stirring was continued for 1 hr after completion of the dropwise addition.
2. 6.00 g (57 mmol) of L-serine was added to the above reaction system and the reaction was heated to reflux for 10 hours.
3. After completion of the reaction, the solvent was removed by distillation under reduced pressure to give 9.05 g of the white solid product L-serine ethyl ester hydrochloride (III) in 93.4% yield.
