GENERAL PROCEDURE: Thionyl chloride (SOCl, 21.8 mL, 0.3 mol) and (S)-alanine (8.91 g, 0.1 mol) were added sequentially to methanol (CHOH, 100 mL), and the reaction was stirred for 2 hours at room temperature. After completion of the reaction, the solvent was removed by distillation under reduced pressure. The residue was dissolved in methanol (30 mL) and again distilled under reduced pressure to remove the organic solvent. This dissolution-distillation process was repeated twice. The final colorless amorphous solid product, D-alanine methyl ester hydrochloride, was obtained with a melting point of 103 °C (literature value 98-99 °C) and a yield of 14.3 g (yield >99%).
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