To readily produce the subject compound useful as a raw material for medicines and polymers by isolating the compound from an opticallyactive basic amino acid and a β-hydroxyasparatic acid salt by using a strongly acidic cation exchange resin. 光学活性β−ヒドロキシアスパラギン酸の光学活性塩基性アミノ酸塩から、強酸性陽イオン交換樹脂を使用して、光学活性β−ヒドロキシアスパラギン酸を容易に得る。 - 特許庁