Patent ID: 7459582

Claim:
A method for producing nateglinide crystals, which comprises: (a) mixing hydrochloric acid and, optionally, one or more acids with a first reaction mixture, said first reaction mixture comprising nateglinide, to obtain a second reaction mixture which is acidic, wherein said first reaction mixture is obtained by reacting trans-4-isopropylcyclohexylcarbonyl chloride with D-phenylalanine in a mixed solvent comprising acetone and water in the presence of potassium hydroxide; (b) adjusting the temperature of said second reaction mixture to 63° C. to 65° C. and the concentration of acetone to more than 8 wt % and less than 22 wt %, maintaining the second reaction mixture at 63° C. to 65° C., and cooling the second reaction mixture to effect precipitation of nateglinide crystals; and (c) isolating the nateglinide crystals.