Example 1; This example demonstrates the synthesis of dimethyl (S)-2-aminosuccinate hydrochloride from L-aspartic acid. The steps were as follows: a solution of L-aspartic acid (13.5 g, 100 mmol) dissolved in 100 ml of methanol was slowly added dropwise to pure thionyl chloride, and the reaction mixture was stirred continuously for 48 hours at room temperature. After completion of the reaction, the reaction mixture was concentrated in vacuum using a rotary evaporator. Subsequently, it was extracted and washed by adding methanol (3 x 30 ml) and dichloromethane (3 x 30 ml) to finally obtain L-aspartic acid dimethyl ester hydrochloride (19.5 g, quantitative yield) in white powder form.
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