title: Preparation and characterisation of oligosaccharides produced by nitrous acid depolymerisation of chitosans.
abstract: Two chitosans with widely different chemical composition (fraction of N-acetylated units (F(A))<0.001 and F(A)=0.59), were degraded by nitrous acid, to obtain the reactive 2,5-anhydro-D-mannose- (M-) unit at the new reducing end. The fully N-acetylated and fully N-deacetylated oligomers were separated by size-exclusion chromatography. Both the chemical structure and purity were studied by one- and two-dimensional 1H and 13C NMR methods. The fully N-acetylated oligomers were found to be stable, whereas the N-deacetylated oligomers reacted intermolecularly by a Schiff base reaction between the 2-amino group on the N-deacetylated units and the M-units, facilitating the cleavage of the glycosidic bond next to the M-unit and the formation of 5-hydroxymethylfurfural (HMF).
authors.affiliation: Norwegian Biopolymer Laboratory (NOBIPOL), Department of Biotechnology, Norwegian University of Science and Technology (NTNU), N-7491, Trondheim, Norway. kt@chembio.ntnu.no
authors.forename: K
authors.initials: K
authors.lastname: Tømmeraas
authors.forename: K M
authors.initials: KM
authors.lastname: Vårum
authors.forename: B E
authors.initials: BE
authors.lastname: Christensen
authors.forename: O
authors.initials: O
authors.lastname: Smidsrød
mesh_terms: D000107:Acetylation; D002240:Carbohydrate Sequence; D002686:Chitin / Q000031:analogs & derivatives / Q000737:chemistry* / Q000378:metabolism; D048271:Chitosan; D002845:Chromatography / Q000379:methods; D009682:Magnetic Resonance Spectroscopy; D008969:Molecular Sequence Data; D015394:Molecular Structure; D009608:Nitrous Acid / Q000737:chemistry*; D009844:Oligosaccharides / Q000737:chemistry* / Q000378:metabolism
chemical_list: D009844:Oligosaccharides; D002686:Chitin; D048271:Chitosan; D009608:Nitrous Acid