METHODS FOR PRODUCING NATEGLINIDE CRYSTALS

There is provided methods for producing nateglinide crystals, which comprises the steps of adding an acid(s) to a reaction mixture containing nateglinide to make it acidic, the reaction mixture being obtained by reacting trans-4-isopropylcyclohexylcarbonyl chloride with D-phenylalanine in a mixed solvent of ketone solvent and water in the presence of an alkali; and then adjusting the temperature of the mixture to 58° C. to 72° C. and the concentration of ketone solvent to more than 8 wt % and less than 22 wt % to conduct precipitation of nateglinide crystals. This producing method is the industrially beneficial methods for crystallization of nateglinide.