5391-17-3Relevant articles and documents
Synthesis of alkyl α- and β-d-glucopyranoside-based chiral crown ethers and their application as enantioselective phase-transfer catalysts
Pálv?lgyi, ádám,Rapi, Zsolt,Ozohanics, Olivér,Tóth, Gábor,Keglevich, Gy?rgy,Bakó, Péter
, p. 1627 - 1645 (2017/11/16)
Chiral monoaza-15-crown-5-type lariat ethers annelated to alkyl 4,6-O-benzylidene-α- and β-d-glucopyranosides have been synthesized. These macrocycles generated significant asymmetric induction as phase-transfer catalysts in a few two-phase reactions. The catalytic effect of the lariat ethers with methoxy, ethoxy, and i-propoxy substituents on C-1 of the sugar unit in both α and β positions was compared. In liquid–liquid two-phase reactions, the nature and position of the substituents did not have much effect. The α-anomers were somewhat more efficient in terms of enantioselectivity than the β forms. In asymmetric Darzens condensations, in the epoxidation of trans-chalcone, in the Michael addition of β-nitrostyrene and diethyl acetamidomalonate, and in the reaction of 2-benzylidene-1,3-indandione with diethyl bromomalonate, maximum enantioselectivities of 73, 94, 78, and 72%, respectively, were obtained in presence of glucopyranoside-based lariat ethers as catalysts.
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.
Direct glycosylation of bioactive small molecules with glycosyl iodide and strained olefin as acid scavenger
Gu, Xiangying,Chen, Lin,Wang, Xin,Liu, Xiao,You, Qidong,Xi, Wenwei,Gao, Li,Chen, Guohua,Chen, Yue-Lei,Xiong, Bing,Shen, Jingkang
, p. 1100 - 1110 (2014/03/21)
A new strategy for diversity-oriented direct glycosylation of bioactive small molecules was developed. This reaction features (-)-β-pinene as acid scavenger and work with glycosyl iodides under mild conditions. With the aid of RP-HPLC and chiral SFC separation techniques, the new direct glycosylation proved effective at gram scale on bioactive small molecules including AZD6244, podophyllotoxin, paclitaxel, and docetaxel. Interesting glycoside derivatives were efficiently created with good yields and 1,2-cis selectivity.
