To provide a method for improving optical purity of an optically active 2-hydroxycarboxylic acid or a derivative thereof, which is useful as a raw material in the manufacture of medicines, agrochemicais, and industrial products. The method of the invention for improving purity of a hydroxycarboxylic acid of the following formula (1a) or (1b) or a derivative thereof includes the steps of reacting the hydroxycarboxylic acid of the following formula (1a) or (1b) with at least one optically inactive base selected from the group consisting of an alkali metal, alkoxide and a secondary amine in the presence of a solvent and, subsequently, performing recrystallization, to thereby form a hydroxycarboxylic acid salt of the following formula (IIIa) or (IIIb):
wherein R
1
represents a C
1-8
alkyl group, and R
2
represents an alkali metal or a secondary amine.
提供一种改善光学纯度的方法,用作药品、农药和工业产品的原料,该方法用于改善下列式(1a)或(1b)的羟基
羧酸或其衍
生物的纯度,包括以下步骤:将下列式(1a)或(1b)的羟基
羧酸与所述溶剂中的所述碱
金属、碱
金属醇盐和二级胺中至少一种选择的光学不活性碱反应,随后进行再结晶,从而形成下列式(IIIa)或(IIIb)的羟基
羧酸盐:其中R1代表C1-8烷基基团,R2代表碱
金属或二级胺。