PURPOSE: To crystallize L-phenonylalamine monomethyl sulfate in a simple operation in higher crystallization yield in the presence of an inorganic, organic acid or ammonium salt of an alkali (alkaline earth) metal.
CONSTITUTION: The objective sulfate is crystallized from an aqueous solution containing (A) L-phenylalanine and (B) monomethyl. sulfate in the presence of an inorganic, organic acid or ammonium salt of an alkali (alkaline earth) metal ' (specifically, e.g. NaCl, C'Cl2, CH3C02Na, NH4Cl). The above aqueous solution is prepared by, preferably, the following process: a reaction liquor obtained by esterification from the component A and methanol in the presence of sulfuric acid is neutralized with a base in the presence of water to form L-phenylalanine methyl ester which is then put to extraction with an organic solvent followed by conducting a layer separation and the resultant aqueous layer is made acidic.
SUGIYAMA NAOKO
TAKEMOTO TADASHI
