Patent ID: 8273916

Claim:
A process for producing (2R)-2-propyloctanoic acid having an optical purity of 99.5% e.e. or more, which comprises: dissolving (2R)-2-propyloctanoic acid having an optical purity of 70% e.e. or more and dibenzylamine in a solvent to give a solution; repeating the following steps (1)-(3) 0 to 3 times: (1) preferentially crystallizing a crystal comprising the (2R)-2-propyloctanoic acid with dibenzylamine from the solution; (2) separating and collecting the precipitated crystal; (3) dissolving the crystal in a solvent to give a solution; preferentially crystallizing a crystal comprising the (2R)-2-propyloctanoic acid with dibenzylamine from the solution; and separating, collecting, back-extracting and extracting the precipitated crystal to give a free (2R)-2-propyloctanoic acid.