title: Synthesis of aryl 3-O-beta-cellobiosyl-beta-D-glucopyranosides for reactivity studies of 1,3-1,4-beta-glucanases.
abstract: A series of substituted aryl beta-glycosides derived from 3-O-beta-cellobiosyl-D-glucopyranose with different phenol-leaving group abilities as measured by the pKa of the free phenol group upon enzymatic hydrolysis has been synthesised. Aryl beta-glycosides with a pKa of the free phenol leaving group > 5 were prepared by phase-transfer glycosidation of the per-O-acetylated alpha-glycosyl bromide with the corresponding phenol, whereas the 2,4-dinitrophenyl beta-glycoside was obtained by condensation of 1-fluoro-2,4-dinitrobenzene with the partially acetylated trisaccharide followed by acid de-O-acetylation. The aryl beta-glycosides have been used for reactivity studies of the wild-type Bacillus licheniformis 1,3-1,4-beta-D-glucan 4-glucanohydrolase. The Hammett plot log kcat versus pKa is biphasic with an upward curvature at low pKa values suggesting a change in transition-state structure depending on the aglycon.
authors.affiliation: Department of Organic Chemistry, Institut Químic de Sarrià, Universitat Ramon Llull, Barcelona, Spain.
authors.forename: A
authors.initials: A
authors.lastname: Planas
authors.forename: M
authors.initials: M
authors.lastname: Abel
authors.forename: O
authors.initials: O
authors.lastname: Millet
authors.forename: J
authors.initials: J
authors.lastname: Palasí
authors.forename: C
authors.initials: C
authors.lastname: Pallarés
authors.forename: J L
authors.initials: JL
authors.lastname: Viladot
mesh_terms: D001407:Bacillus / Q000201:enzymology*; D002236:Carbohydrate Conformation; D002240:Carbohydrate Sequence; D005960:Glucosides / Q000138:chemical synthesis* / Q000737:chemistry / Q000378:metabolism; D007700:Kinetics; D008969:Molecular Sequence Data; D019906:Nuclear Magnetic Resonance, Biomolecular; D009844:Oligosaccharides / Q000138:chemical synthesis* / Q000737:chemistry / Q000378:metabolism
chemical_list: D005960:Glucosides; D009844:Oligosaccharides