Isolation and identification of 2-deoxy-2,3-dehydro-N-acetylneuraminic acid from the urine of a patient with sialuria.

N-Acetylneuraminic acid preparations from the urine of a patient with sialuria contain 1--2% of 2-deoxy-2,3-dehydro-N-acetylneuraminic acid. This new human sialic acid was isolated by ion-exchange and partition chromatography. The structure has been elucidated by mass spectrometry and confirmed by comparison with the synthetic compound. The properties of this unsaturated sialic acid in the orcinol/Fe3+/HCl and the periodic acid/thiobarbituric acid tests as well as in thin-layer and gas-liquid chromatography are described. It does not react with acylneuraminate pyruvatelyase. The origin of this new human sialic acid is discussed.