Method of preparing methyl ester and its hydrochloride

摘要

A method of preparing alpha -L-phenylalanine methyl ester and its hydrochloride, which comprises dissolving alpha -L-aspartyl-L-phenylalanine beta -methyl ester in a methanol/hydrochloric acid mixture solvent which contains, when hydrochloric acid is expressed in terms of concentrated hydrochloric acid and water, 0 to 20% by volume of methanol, 8 to 55% by volume of concentrated hydrochloric acid and water (balance) in a concentration from 0.01 mol/dl to 0.3 mol/dl; holding the solution at 0 DEG to 60 DEG C. to effect intramolecular ester exchange reaction and crystallize out the formed alpha -L-aspartyl-L-phenylalanine methyl ester as its hydrochloride; isolating the hydrochloride; and obtaining, when required, the free ester by neutralization with an alkali, is disclosed.