Method of separating optically active dihydroxy-heptenoic acid esters

A method of separating optically active dihydroxyheptenoic acid esters from a solution comprising a mixture of optical isomers of a dihydroxyheptenoic acid ester represented by the formula (1) below

• wherein Ar represents an aromatic group that may have nitrogen, oxygen, and a condensed ring, and have a group selected from a hetero-group having nitrogen and/or oxygen, a halogen group, and a hydrocarbon group which is an alkyl group or phenyl group and may have the hetero-group and the halogen group, R1 represents a linear or branched chain alkyl group having 1 to 20 carbon atoms, a phenyl group, or an aralkyl group having 7 to 18 carbon atoms
• by liquid chromatography in which a packing material comprising a carrier and a first polysaccharide carried on the carrier is used,
• wherein the first polysaccharide is formed by substituting for a portion or all of hydrogen atoms in hydroxyl groups and amino groups of a second polysaccharide by one of the groups represented by the formula (2) below and the formula (3) below:
• wherein R2 represents a linear or branched chain alkyl group having 2 to 8 carbon atoms
• wherein R2 represents a linear or branched chain alkyl group having 2 to 8 carbon atoms.