Highly efficient enzymatic synthesis of Galβ-(1→3)-GalNAc and Galβ-(1→3)-GlcNAc in ionic liquids
摘要:
Ionic liquids (ILs) have emerged as an alternative to conventional organic media due to their high thermal and chemical stability, negligible vapour pressure, non-flammability and easy recycling. In this context, this work assesses the catalytic activity of a beta-galactosidase from Bacillus circulans ATCC 31382 (beta-Gal-3-NTag) in the synthesis of beta-(1 -> 3)-galactosides using different ILs. A noticeably increase in activity, retaining total regioselectivity was found in the synthetic behaviour of B. circulans beta-galactosidase in ILs as co-solvents and using a 1:5 molar ratio of donor (pNP-beta-Gal):acceptor (GlcNAc or GalNac). Yields up to 97% of beta-(1 -> 3) with different ILs were found. These reactions take place without noticeable hydrolytic activity and with total regioselectivity, representing a considerable improvement over the use of aqueous buffer or conventional organic solvents. Furthermore, reaction scaling up and IL recovery and recycling are feasible without losing catalytic action. Molecular modelling studies performed predict a three-dimensional interaction at the active centre between the acceptor and the water-IL mixture, which could explain the results obtained. (C) 2013 Elsevier Ltd. All rights reserved.
The Diels-Alder reaction between cyclopentadiene and three dienophiles (acrolein, methyl acrylate and acrylonitrile) having different hydrogen bond acceptor abilities has been carried out in several ionic liquids and molecular solvents in order to obtain information about the factors affecting reactivity and selectivity. The solvent effects on these reactions are examined using multiparameter linear
Kinetic Study of ThermalZ toE Isomerization Reactions of Azobenzene and 4-Dimethylamino-4′-nitroazobenzene in Ionic Liquids [1-R-3-Methylimidazolium Bis(trifluoromethylsulfonyl)imide with R=Butyl, Pentyl, and Hexyl]
which indicated that the slow isomerization through the inversion mechanism with a nonpolar transition state was little influenced by the solvent properties, such as the viscosity and dielectric constant, of ionic liquids. On the other hand, the rate constants and the corresponding frequency factors of the Arrhenius plot were significantly reduced for the isomerization of 4-dimethylamino-4'-nitroazobenzene
Pseudo-Encapsulation-Nanodomains for Enhanced Reactivity in Ionic Liquids
作者:Cameron C. Weber、Anthony F. Masters、Thomas Maschmeyer
DOI:10.1002/anie.201206113
日期:2012.11.12
domains within 1‐alkyl‐3‐methylimidazolium ionicliquids can affect reaction outcomes by pseudo‐encapsulation of reactants and this has been explored for a nucleophilic substitution reaction using a cationic substrate and a range of nucleophiles. The significant rate enhancements observed correlate with the concentration of the polar reactants within the ionicliquid's polar domain. ([CnMIM]=1‐alkyl‐3‐methylimidazolium)
域受限:1-烷基-3-甲基咪唑鎓离子液体中的极性和非极性域可通过反应物的假包封影响反应结果,这已被探索用于使用阳离子底物和一系列亲核试剂的亲核取代反应。观察到的显着速率提高与离子液体极性域中极性反应物的浓度相关。([C n MIM] = 1-烷基-3-甲基咪唑鎓)。
Solvent Extraction of Sr<sup>2+</sup> and Cs<sup>+</sup> Based on Room-Temperature Ionic Liquids Containing Monoaza-Substituted Crown Ethers
作者:Huimin Luo、Sheng Dai、Peter V. Bonnesen
DOI:10.1021/ac035473d
日期:2004.5.1
A series of N-alkyl aza-18-crown-6 ethers were synthesized and characterized by NMR spectroscopy and mass spectrometry. These monoaza-substituted crown ethers in ionic liquids were investigated as recyclable extractants for separation of Sr2+ and Cs+ from aqueous solutions. The pH-sensitive complexation capability of these ligands allows for a facile stripping process to be developed so that both macrocyclic ligands and ionic liquids can be reused. The extraction efficiencies and selectivities of these monoaza-substituted crown ethers for Na+, K+, Cs+, and Sr2+ were studied in comparison to those of dicyclohexano-18-crown-6 under the same conditions. The extraction selectivity order for dicyclohexano-18-crown-6 in the ionic liquids investigated here was K+ ≫ Sr2+ > Cs+ > Na+. The extraction selectivity order for N-alkyl aza-18-crown-6, in which the alkyl group is varied systematically from ethyl to n-dodecyl, was Sr2+ ≫ K+ > Cs+ > Na+ in 1-ethyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]amide and 1-butyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]amide and K+ > Sr2+ > Cs+ > Na+ in 1-hexyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl] amide and 1-octyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]amide. The strong dependence of selectivity on the type of ionic liquid indicates an important role played by solvation in solvent extraction processes based on ionic liquids. The optimization of macrocyclic ligands and ionic liquids led to an extraction system that is highly selective toward Sr2+.
Probing CO
<sub>2</sub>
Reduction Pathways for Copper Catalysis Using an Ionic Liquid as a Chemical Trapping Agent
作者:Gui‐Rong Zhang、Sascha‐Dominic Straub、Liu‐Liu Shen、Yannick Hermans、Patrick Schmatz、Andreas M. Reichert、Jan P. Hofmann、Ioannis Katsounaros、Bastian J. M. Etzold
DOI:10.1002/anie.202009498
日期:2020.10.5
of high‐performance electrocatalysts. The development process relies heavily on trial and error methods due to poor mechanistic understanding of the reaction. Demonstrated here is that ionicliquids (ILs) can be employed as a chemical trapping agent to probe CO2RR mechanistic pathways. This method is implemented by introducing a small amount of an IL ([BMIm][NTf2]) to a copper foam catalyst, on which