Structure determination of N-acetyl amino sugar derivatives and disaccharides by gas chromatography and mass spectroscopy

Abstract

Gas chromatography retention times and mass spectra fragmentation patterns were obtained for the trimethylsilyl ethers of 2-acetamindo-2-deoxy- d-glucose, -galactose, and -mannose, (GlcNAc, GalNAc, and ManNAc, respectively), β-1,3-dimethoxy-GlcNAc, the α- and β-methoxy glycosides of GlcNAc and GalNAc, the α- and β-methoxy furanosides of GalNAc, and β-1-4 and β-1-6 linked 2,2′-diacetamido-2,2-dideoxy-glucosylglucoses, and a glycopeptide linkage compound, 2-acetamido-1- N-β- l-aspartyl-2-deoxy-β- d-glycopyranosylamine (GlcNAc-Asn). The mass spectra of these derivatives are discussed in detail. From the mass spectra of the trimethylsilyl derivatives of the free and partially methylated monosaccharides it is possible to determine which and how many positions are methylated and whether the ring is in the pyranose or furanose form. Fragmentation patterns of trimethylsilyl disaccharide derivatives show that it is possible to determine linkage position. Anomeric configuration and other steriochemical features such as axial or equatorial configuration cannot be easily determined from fragmentation patterns but can be determined from gas chromatography retention times, optical rotatory dispersion, and circular dichroism (3). A combination of these methods provides a means of solving the structural and stereochemical problems of carbohydrates.