IDENTIFICATION OF SIALIC-ACID AND RELATED ACIDS AS ACETYLATED LACTONES BY GAS-CHROMATOGRAPHY MASS-SPECTROMETRY

A procedure for characterization of sialic acid-like monosaccharides, i.e. 3-deoxy-2-ulosonic acids, by gas chromatography/mass spectrometry is described. The free monosaccharides were reduced with NaBH4 and th e resulting 3-deoxyaldonic acids were acetylated. Five-membered ring l actones were obtained as the major products. The keto-deoxy compounds N-acetylneuraminic acid, N-glycolylneuraminic acid, 3-deoxy-D-manno-2- octulosonic acid and 3-deoxy-D-glycero-D-galacto-2-nonulosonic acid we re investigated. A detailed study of the electron impact ionization fr agmentation pathways of the acetylated lactones were conducted using t andem mass spectrometry, The mass spectra allowed unambiguous structur al identification of the acidic monosaccharides.