31046-14-7Relevant academic research and scientific papers
Solvent and α-secondary kinetic isotope effects on β-glucosidase
Xie, Miaomiao,Byers, Larry D.
, p. 1776 - 1781 (2015/03/30)
β-Glucosidase from sweet almond is a retaining, family 1, glycohydrolase. It is known that glycosylation of the enzyme by aryl glucosides occurs with little, if any, acid catalysis. For this reaction both the solvent and α-secondary kinetic isotope effects are 1.0. However, for the deglucosylation reaction (e.g., kcat for 2,4-dinitrophenyl-β-D-glucopyranoside) there is a small solvent deuterium isotope effect of 1.50 (± 0.06) and an α-secondary kinetic isotope effect of 1.12 (± 0.03). For aryl glucosides, kcat/KM is very sensitive to the pKa of the phenol leaving group [βlg - 1; Dale et al., Biochemistry 25 (1986) 2522-2529]. With alkyl glucosides the βlg is smaller (between - 0.2 and - 0.3) but still negative. This, coupled with the small solvent isotope effect on the pH-independent second-order rate constant for the glucosylation of the enzyme with 2,2,2-trifluoroethyl-β-glucoside [D2O(kcat/KM) = 1.23 (± 0.04)] suggests that there is more glycone-aglycone bond fission than aglycone oxygen protonation in the transition state for alkyl glycoside hydrolysis. The kinetics constants for the partitioning (between water and various alcohols) of the glucosyl-enzyme intermediate, coupled with the rate constants for the forward (hydrolysis) reaction provide an estimate of the stability of the glucosyl-enzyme intermediate. This is a relatively stable species with an energy about 2 to 4 kcal/mol higher than that of the ES complex. This article is part of a Special Issue entitled: Enzyme Transition States from Theory and Experiment.
The role of sugar substituents in glycoside hydrolysis
Namchuk, Mark N.,McCarter, John D.,Becalski, Adam,Andrews, Trevor,Withers, Stephen G.
, p. 1270 - 1277 (2007/10/03)
A series of monosubstituted deoxy and deoxyfluoro 2,4-dinitrophenyl (DNP) β-D-glycopyranosides was synthesized and used to probe the mechanism of spontaneous β-glycoside hydrolysis. Their relative rates of hydrolysis followed the order 2-deoxy > 4-deoxy > 3-deoxy ? 6-deoxy > parent > 6-deoxy- 6-fluoro > 3-deoxy-3-fluoro > 4-deoxy-4-fluoro > 2-deoxy-2-fluoro. Hammett correlations of the pH-independent hydrolysis rates of each of the 6-, 4-, 3- , and 2-position substituted glycosides with the σ1 value for the sugar ring substituent were linear (r = 0.95 to 0.999, π(I) = -2.2 to -10.7), consistent with hydrolysis rates being largely dictated by field effects on an electron-deficient transition state. The relative rates of hydrolysis of the DNP glucosides can be rationalized on the basis of the stabilities of the oxocarbenium ion-like transition states, as predicted by the Kirkwood- Westheimer model. The primary determinant of the rate of hydrolysis within a series appears to be the field effect of the ring substituent on O5, the principal center of charge development at the transition state. Differences in the rates of hydrolysis between different series of hexopyranosides may not arise solely from field effects and likely also reflect differences in steric factors or solvation.
Direct anomeric O-arylation and O-hetarylation of glucose electron deficient aromatic and hetaromatic compounds in aryl and hetaryl glycoside synthesis
Huchel, Ursula,Schmidt, Christoph,Schmidt, Richard R.
, p. 9457 - 9460 (2007/10/02)
Anomeric O-arylation and O-hctarylation of tetra-O-bcnzyl-, tetra-O-acctyl-, and O-unprotected glucose (1a-c) can be directly performed with electron dcficienl aromatic and hctcroaromatic systems having fluoro- (2A-2F) or phenylsulfonyl (3B, 3G-3K), respectively, as leaving groups. The reactions were carried out in DMF as solvent at room temperature with NaH as the base; they led in the products 4 to an exchange of the leaving group by the glucopyranosyloxy moicly; mainly β-products were obtained.
Single step stereoselective synthesis of unprotected 2,4-dinitrophenyl glycosides
Sharma, Sunil K.,Corrales, Guillermo,Penades, Soledad
, p. 5627 - 5630 (2007/10/02)
Unprotected 2,4-dinitrophenyl glycosides have been synthesized in a single step by the reaction of mono- and disaccharides with 1-fluoro-2,4-dinitrobenzene in the presence of a solution of sodium bicarbonate.
