title: 3-deoxypentosulose: an alpha-dicarbonyl compound predominating in nonenzymatic browning of oligosaccharides in aqueous solution.
abstract: The thermal degradation of D-glucose, maltose, and maltotriose in aqueous solution was investigated under caramelization (no glycine) and Maillard (with glycine) conditions. Degradation of the sugar and alpha-dicarbonyls product was monitored. Under both caramelization and Maillard reaction conditions, 3-deoxypentosulose was the predominating alpha-dicarbonyl compound formed from maltose and maltotriose. In the absence of an amino compound, however, 3-deoxypentosulose is formed in much lower concentration. It was concluded that 3-deoxypentosulose is formed by a pathway specific for oligo- and polysaccharides since this alpha-dicarbonyl is formed from the alpha-1-->4 glucans such as maltose and maltotriose but not from glucose. For its formation, a retro Claisen reaction of an enolization product of 1-amino-1,4-dideoxyhexosulose is proposed as the route to its formation. 1-Amino-1,4-dideoxyhexosulose could be formed by vinylogous alpha-elimination from the 2,3-enediol structure after Amadori rearrangement, favored by planar alignment of the bonds between C1 and C4. Subsequent rearrangement by keto-enoltautomerization leads to a 1-imino-3-keto structure. In this structure, attack of a hydroxyl anion, provided by water at neutral pH, could cause a splitting off of the C1. This reaction gives rise to formic acid or formamide and a pentose derivative, which reacts further to give 3-deoxypentosulose.
authors.affiliation: Institut für Lebensmittelchemie, Technische Universität Berlin, Gustav-Meyer-Allee 25, D-13355 Berlin, Germany.
authors.forename: Anke
authors.initials: A
authors.lastname: Hollnagel
authors.forename: Lothar W
authors.initials: LW
authors.lastname: Kroh
mesh_terms: D005947:Glucose / Q000737:chemistry; D005998:Glycine / Q000737:chemistry; D006358:Hot Temperature; D007661:Ketoses / Q000737:chemistry*; D015416:Maillard Reaction; D008320:Maltose / Q000737:chemistry; D009844:Oligosaccharides / Q000737:chemistry*; D012996:Solutions; D014312:Trisaccharides / Q000737:chemistry; D014867:Water
chemical_list: D007661:Ketoses; D009844:Oligosaccharides; D012996:Solutions; D014312:Trisaccharides; D014867:Water; C008317:maltotriose; C048054:3-deoxy-glycero-pentos-2-ulose; D008320:Maltose; D005947:Glucose; D005998:Glycine