Hydrochloric Acid → N-(N-Formyl-L-alpha-aspartyl)-3-phenyl-L-alanine

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This invention relates to a preparation process of α-L-aspartyl-L-phenylalanine methyl ester or its hydrochloride. More specifically, this invention provides a process for preparing α-L-aspartyl-L-phenylalanine methyl ester or its hydrochloride which process comprises: condensating N-formyl-L-aspartic acid anhydride and L-phenylalanine in water at a pH in the range of 7-12 to form N-formyl-α-L-aspartyl-L-phenylalanine; acidifying the reaction mixture with hydrochloric acid in the presence of methanol without isolating the N-formyl-α-L-aspartyl-L-phenylalanine so as to bring it into contact with hydrochloric acid in the presence of methanol for reaction and thereby to precipitate α-L-aspartyl-L-phenylalanine methyl ester hydrochloride; separating the α-L-aspartyl-L-phenylalanine methyl ester hydrochloride; and neutralizing said hydrochloride as required. Further, this invention provides another process for preparing α-L-aspartyl-L-phenylalanine methyl ester or its hydrochloride which process comprises: condensating N-formyl-L-aspartic acid anhydride and L-phenylalanine in water containing methanol in an amount of 6 moles or less per mol of the L-phenylalanine at a pH in the range of 7-12 to form N-formyl-α-L-aspartyl-L-phenylalanine; acidifying the reaction mixture with hydrochloric acid without isolating the N-formyl-α-L-aspartyl-L-phenylalanine so as to bring it into contact with hydrochloric acid in the presence of methanol for reaction and thereby to precipitate α-L-aspartyl-L-phenylalanine methyl ester hydrochloride; separating the α-L-aspartyl-L-phenylalanine methyl ester hydrochloride; and neutralizing said hydrochloride as required.

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