A simple and efficient one-step, regioselective, enzymatic glucosylation of arbutin by α-glucosidase

4-Hydroxyphenyl-β-isomaltoside has been synthesized by α-glucosidase assisted transglycosylation between arbutin as acceptor and sucrose as donor molecules, respectively. Optimum conditions for the transglucosylation reaction were 40 °C for 20 h with 10 mM arbutin and 1.5 M sucrose in a 100 mM sodium citrate/phosphate buffer at pH 5.0. The new glucoside was obtained in a 50% molar yield with respect to arbutin.     

Probing in vitro digestion at oil–water interfaces

Interfacial layers have been widely applied to study the formation and stability of emulsion-based systems. However, the application of isolated interfaces to address digestibility of emulsions is often limited because of the complexity of experimental methods and results. This review summarizes the latest developments in analytical methods and literature data on effects of digestion on interfacial layers. Particular emphasis is given to understand the changes on interfacial magnitudes during oral, gastric, and duodenal digestion, either applied separately or sequentially. Limitations of interfacial aspects and key factors that influence emulsion microstructure in bulk and lipid digestion are identified. Understanding the behavior of interfacial layers upon gastrointestinal digestion promotes an accurate tracking of the physiological fate of emulsions.     

A DFT study of lithium battery materials: application to the β-VOXO4 systems (X=P, As, S)

VOXO₄ systems have been considered as potential lithium battery electrodes. They mainly present two distinct structural types: the tetragonal “α” type with a two-dimensional framework, and the three-dimensional orthorhombic “β”. DFT calculations were performed on this latter system for several β-Li_xVOXO₄ compounds (x=0, 1; X=P, As, S). They allowed to propose structural models for VOAsO₄ and LiVOSO₄, not fully crystallographically well described yet. Based on an experimental model of two-phase processes, these calculations led also to a good simulation of electrochemical potential values. A density of states analysis put in evidence the “inductive effect” and the role played by (XO₄)ⁿ⁻ groups inside the host frameworks on these potentials.     

Stereoselective synthesis of (Z)-γ-cyano-β-perfluoroalkyl-β,γ-unsaturated esters

(Z)-γ-Cyano-β-perfluoroalkyl-β,γ-unsaturated esters have been synthesized by the reaction of perfluoroacylated phosphonates with organozinc reagent in 50-71% (three steps) yields.     

制备1—氰基—2,3,5—三—O—苯甲酰基—β—D—呋喃核糖的简便方法

制备１┐氰基┐２，３，５┐三┐Ｏ┐苯甲酰基┐β┐Ｄ┐呋喃核糖的简便方法张万轩＊雷策南黄锦霞陈家威（湖北大学化学系武汉４３００６２）关键词鸟苷，制备，氰基三苯甲酰基－β－Ｄ－呋喃核糖，三甲基氯硅烷１９９６－０８－１２收稿，１９９７－０３－０５修回１－氰...     

Copper(II) tetrafluoroborate as a novel and highly efficient catalyst for Michael addition of mercaptans to α,β-unsaturated carbonyl compounds

Copper(II) tetrafluoroborate has been found to be a new and highly efficient catalyst for Michael addition of thiols to α,β-unsaturated carbonyl compounds under solvent-free conditions and in H₂O at room temperature. The reactions are very fast and are completed in 2 min to 1 h affording high yields. The rate of thiol addition was dependent on the steric hindrance at the β-carbon of the α,β-unsaturated carbonyl substrate. In the case of chalcones, the reactions are best carried out in MeOH as solvent.     

A simpler and greener protocol for the preparation of β-acetylamino ketones by a one-pot reaction of aryl aldehydes, enolisable ketones, acetyl chloride and acetonitrile in the presence of zeolite Hβ as a reusable catalyst

β-Acetylamino ketones have been obtained in a one-pot coupling of an aldehyde with an enolisable ketone, acetyl chloride and acetonitrile in the presence of zeolite Hβ as catalyst at room temperature (26-28 °C). The procedure has the advantages of mild workup, circumvention of high temperature and inert atmosphere. The catalyst was found to be recyclable.     

Optimisation of the chlorthalidone chiral separation by capillary electrochromatography using an achiral stationary phase and cyclodextrin in the mobile phase

The separation of chlorthalidone enantiomers in capillary electrochromatography on an achiral stationary phase when adding a chiral selector, hydroxypropyl-β-cyclodextrin, to the mobile phase, was optimised. The goal was to investigate the feasibility of modelling retention times and resolution when during the optimisation procedure regular replacement of columns is required due to their fragility. Therefore, it is essential that the packing procedure delivers reproducible columns. The optimisation of an existing chlorthalidone separation was chosen as case study. The influence of two factors, chiral selector concentration and organic modifier content, on the responses was modelled. The experiments performed prior to modelling were defined by a central composite design. Results on different columns, obtained under identical experimental conditions, were found comparable and thus modelling was possible in situations where several columns were required to complete a design. A second-order polynomial model was built for both responses. Optimal separations were also predicted using Derringer’s desirability functions. The optimum was found at 33 mM cyclodextrin and 16% (v/v) acetonitrile on two types of columns (with different packing times) leading to a strong reduction in analysis time for an equally good separation compared to the initial conditions. Measured and predicted responses were found comparable, indicating that acceptable models were obtained.     

Efficient desulfurization of 2-thiopyrimidine nucleosides to the corresponding 4-pyrimidinone analogues using trans-2-(phenylsulfonyl)-3-phenyloxaziridine

A brief treatment of 2-thiopyrimidine nucleosides (s²U^∗) with trans-2-phenylsulfonyl-3-phenyloxaziridine (PSO) results in efficient substrate desulfurization leading to the corresponding 4-pyrimidinone analogues (H²U^∗). The key transformation proceeds through oxidation of the 2-thiocarbonyl group to a sulfur oxyacid derivative and subsequent elimination of sulfur dioxide. 4-Pyrimidinone 1-β-d-riboside (H²U) has been transformed into the respective phosphoramidite, a ready-to-use monomer for the introduction of a modified nucleoside into an oligonucleotide chain. Moreover, the effective desulfurization of the 2-thiouridine nucleotide could be achieved directly at the oligonucleotide level, by treatment of the TdA(s²U)dGdC oligonucleotide with PSO, as verified by MALDI-TOF mass spectrometry.     

Computational study of conformational preferences of thioamide-containing azaglycine peptides

The effect of thioamide substitution on the conformational stability of an azaglycine-containing peptide, For-AzaGly-NH2 (1), was investigated for the sake of finding possible applications by using ab initio and DFT methods. As model compounds, For-[psiCSNH]-AzaGly-NH2 (2), For-AzaGly-[psiCSNH]-NH2 (3), and For-[psiCSNH]-AzaGly-[psiCSNH]-NH2 (4) were used. Two-dimensional phi-psi potential energy surfaces (PESs) for 2-4 were calculated at the B3LYP/6-31G*//HF/6-31G* level in gas (epsilon = 1.0) and in water (epsilon = 78.4) by applying the isodensity polarizable continuum model (IPCM) method. On the basis of these PESs, the minimum energy conformations for 2-4 were characterized at the B3LYP level with 6-31G*, 6-311G**, and 6-31+G** basis sets. The remarkable structural effect of thioamide substitution for 2-4 is that beta-strand structure is observed as a global or local minimum. The minima of 2-4 are also compared with those for glycine and thioamide-containing glycine peptides. Our theoretical results demonstrate that compounds 2-4 would be used to design controllable secondary structures.