Ajinomoto Co., Ltd.

So Abe

Shinichi Kishimoto

Toshihisa Kato

Hideo Takeda

Kimiyasu Sakamoto

In crystallizing .alpha.-APM from a water solution or a mixed solvent solution of water and a lower alcohol in a crystallizer, the pressure in the crystallizer is held at not higher than atmospheric pressure, a water or water/alcohol mixed solution of .alpha.-APM is fed into the crystallizer with stirring so that the solvent is vaporized, and the crystallization solution is cooled and crystallized by the latent heat of vaporization or is heated so as to prevent supercooling.

Method of crystallizing .alpha.-L-aspartyl-L-phenylalanine methyl ester

In neutralizing an acid addition salt of .alpha.-APM in an aqueous medium, the .alpha.-APM concentration in the neutralized liquid is controlled to fall within the range of from 3 to 10 wt. % at the finish of neutralization. Then, the liquid is heated to 50.degree. to 80.degree. C. and neutralization is effected with stirring to the isoelectric point of .alpha.-APM; or after the neutralization, the neutralized liquid is heated. The neutralized liquid is thereafter cooled with or without stirring so that crystals of .alpha.-APM are precipitated.

Method of preparing .alpha.-L-aspartyl-L-phenylalanine methyl ester

An acid addition salt of .alpha.-APM is dissolved or suspended in an aqueous medium at 50.degree. C. or lower at a pH of 3 or less and a concentration of the salt of 3 wt.% or more (solution A). A liquid having a pH of 3 or more and containing or not containing .alpha.-APM is prepared (solution B) and gradually mixed with solution A with stirring. The temperature of the liquid mixture is kept to be 40.degree. C. or lower and the pH value of the mixture is kept at 3 or more, optionally adding a base thereto, whereby crystals of .alpha.-APM are precipitated out.

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Kawasaki, Japan

So Abe