PROBLEM TO BE SOLVED: To provide a method for manufacturing neuraminic acid derivatives and to provide neuraminic acid derivatives having high purity.SOLUTION: This invention relates to: a compound having formula (I), which has the content of a compound having formula (VII) of 0.5 wt.% or lower, wherein in the formula (VII), Rrepresents a 1-19C alkyl group, Rrepresents a 1-4C alkyl group, and Ac represents an acetyl group, provided that the compound having the formula (I) may contains a compound having formula (II)； or a pharmacologically acceptable salt thereof.【課題】ノイラミン酸誘導体の製造方法、ならびに、高純度のノイラミン酸誘導体の提供。【解決手段】式（ＶＩＩ）［式中、Ｒ1は、Ｃ1－Ｃ19アルキル基を示し、Ｒ2は、Ｃ1－Ｃ4アルキル基を示し、Ａｃは、アセチル基を示す］を有する化合物の含有率が０．５重量％以下である式（Ｉ）を有する化合物［ただし、式（Ｉ）を有する化合物は、式（ＩＩ）を有する化合物を含有してもよい］またはその薬理上許容される塩。【選択図】なし
