66-56-8Relevant articles and documents
Synthesis of aryl 3-O-β-cellobiosyl-β-D-glucopyranosides for reactivity studies of 1,3-1,4-β-glucanases
Planas, Antoni,Abel, Mireia,Millet, Oscar,Palasi, Josep,Pallares, Cristina,Viladot, Josep-Lluis
, p. 53 - 64 (2007/10/03)
A series of substituted aryl β-glycosides derived from 3-O-β-cellobiosyl-D-glucopyranose with different phenol-leaving group abilities as measured by the pK(a) of the free phenol group upon enzymatic hydrolysis has been synthesised. Aryl β-glycosides with a pK(a) of the free phenol leaving group>5 were prepared by phase-transfer glycosidation of the per-O-acetylated α-glycosyl bromide with the corresponding phenol, whereas the 2,4-dinitrophenyl β-glycoside was obtained by condensation of 1-fluoro-2,4-dinitrobenzene with the partially acetylated trisaccharide followed by acid de-O-acetylation. The aryl β-glycosides have been used for reactivity studies of the wild-type Bacillus licheniformis 1,3-1,4-β-d-glucan 4-glucanohydrolase. The Hammett plot log k(cat) versus pK(a) is biphasic with an upward curvature at low pK(a) values suggesting a change in transition-state structure depending on the aglycon. Copyright (C) 1998 Elsevier Science Ltd.
Synthese von Di- und Tri(o-phenylendiamin)-Liganden
Hahn, Ekkehardt F.,Dittler-Klingemann, Andreas
, p. 779 - 782 (2007/10/02)
The o-phenylenediamine ligand trisamine, TRIPACEN (4) and bisamine, DIPACEN (8) are obtained by Williamson coupling of the potassium salt of 2,3-dinitrophenole (1) to tris(3-chlorpropyl)amine (2) or benzylbis(3-chlorpropyl)amine (5), respectively, followed by reduction of the nitro functions with Sn/HCl or Pd(OH)2/H2.
Effective Charge Distribution for Attack of Phenoxide Ion on Aryl Methyl Phosphate Monoanion: Studies Related to the Action of Ribonuclease
Ba-Saif, Salem A.,Davis, Andrew M.,Williams, Andrew
, p. 5483 - 5486 (2007/10/02)
The reaction of phenoxide ion with aryl methyl phosphate monoanions and aryl diethyl phosphates obeys second-order kinetics in aqueous solution at 39 deg C and 1 M ionic strength.The second-order rate constants (M-1s-1) for these reaction obey the following Broensted equations: log k2 = -0.51pKlg + 0.72 (r = 0.970) (aryl diethyl phosphate) log k2 = -0.64pKlg - 2.53 (r = 0.898) (aryl methyl phosphate monoanion) The monoanion is some 104-fold less reactive toward attack by phenolate ion than is the diethyl ester with 4-nitrophenol leaving group, consistent in part with the operation of an electrostatic effect.The similarity between the Broensted exponents in both reactions indicates that the effective charge change on the leaving oxygen from ground state to transition state is similar in both cases; this indicates that the oxyanion in the monoanion case does not assist leaving group expulsion.The date are consistent with little coupling between proton abstraction from the 2'-hydroxyl group and the leaving group expulsion in the ribonuclease reaction.