Abstract: A method is provided for supplying the desired optical isomer of a derivative of epoxypropionic acid from a racemix mixture. A representative derivative of epoxypropionic acid is an ester of (p-methoxyphenyl)epoxypropionic acid. The racemic mixture initially is dissolved in carbon dioxide and the resulting solution is passed through a chromatographic column. The desired isomer is subsequently separated from the resulting eluant. In a preferred embodiment the chromatographic column is packed with microcrystallized cellulosetriacetate, cellulose-tris-(3,5-dimethylphenylcarbamate), or cellulose-tris-(p-methylphenylcarbamate).