Un nouveau type de sucres azotés,les gem-azo-alcools. Communication préliminaire

Treatment of keto-sugar p-nitrophenylhydrazones with lead tetraacetate led to the corresponding gem-azo-acetates. The reaction is highly stereoselective, only one of the two possible epimers at the new asymmetric carbon being formed in measurable quantity. Catalytic de-acylation of these gem-azo-acetates yielded, quantitatively, representatives of a new class of nitrogen-containing sugars: the gem-azo-alcohols. When treated with potassium t-butylate, the gem-azoacetates underwent a rearrangement with ring expansion leading to N-aminolactams.     

An Ab Initio Molecular Orbital Theory and Density Functional Theory (DFT) Study of Conformers and Rotamers of 4-Substituted (Methyl, Hydroxymethyl, Methanoyl, Ethanoyl, Cyano, Fluoro, Chloro, Bromo, Acetoxy) Tetrahydro-2H-thiopyran-1,1-dioxides

The structures and energies of axial and equatorial conformers and rotamers of 4-substituted tetrahydro-2H-thiopyran-1,1-dioxides (tetrahydrothiopyran-1,1-dioxides, thiacyclohexane-1,1-dioxides, thiane-1,1-dioxides, and 1,1-dioxothianes; CH₃, CH₂OH, CHO, COCH₃, CN, F, Cl, Br, and OCOCH₃) were calculated using the hybrid density functionals B3LYP, B3P86, and B3PW91, as well as MP2 and the 6-31G(d), 6-31G(2d), 6-31G(3d), 6-31G(d,p), and 6-31+G(d) basis sets. MP2/6-31+G(d)/ /HF/6-31+G(d) [–G° = 1.73 kcal/mol], B3P86/6-31G(d) [–G° = 1.75 kcal/mol], and B3PW91/6-31G(d) [–G° = 1.85 kcal/mol] gave conformational free energy (G°) values at 180 K for 4-methyltetrahydro-2H-thiopyran-1,1-dioxide which were similar to the reported experimental values for methylcyclohexane (–G° = 1.80 kcal/mol), 4-methyltetrahydro-2H-thiopyran (–G° = 1.80 kcal/mol), and other 4-methyl-substituted heterocycles. All levels of theory showed that the conformational preferences of the 4-methanoyl (4-formyl), 4-ethanoyl (4-acetyl), and 4-cyano substituents were small. The HF calculations gave conformational free energy (G°) values for 4-chlorotetrahydro-2H-thiopyran-1,1dioxide which were closer to the experimental value than the MP2 and density functional methods. The best agreement with available experimental data for 4-bromotetrahydro-2H-thiopyran-1,1-dioxide was obtained from the HF/6-31G(2d), HF/6-31G(3d), and B3LYP/6-31G(2d) calculations, and, for 4-acetoxytetrahydro-2H-thiopyran-1,1-dioxide, from the HF/6–31G(3d) calculations. The conformational free energies (G°) and relative energies (E) of the conformers and rotamers have been compared with the correspondingly substituted cyclohexanes and tetrahydro-2H-thiopyrans and are discussed in terms of dipole–dipole (electrostatic) interactions and repulsive nonbonded interactions (steric) in the most stable axial and equatorial conformers. The axial S=O bond lengths are shorter than the equatorial S=O bond lengths and the C2–C3 bond lengths in the substituents with carbon-bonded to the ring are shorter than the C3–C4 and C4–C-5 bond lengths. In contrast, the C2–C3 bond lengths in the 4-halogen and 4-acetoxy substituents are longer than the C3–C4 and C4–C-5 bond lengths.     

Advances,opportunities, and challenges of hydrogen and oxygen production from seawater electrolysis: An electrocatalysis perspective

With increasing energy consumption and greenhouse gas emissions, the importance of developing renewable energy sources to replace fossil fuels has become a vital global task. Hydrogen produced via water electrolysis powered by renewable energy systems at a large scale is an essential measure to reduce greenhouse gas and particulate emissions. Electrolysers use a substantial amount of water (mainly freshwater) to produce hydrogen and oxygen at the cathode, and anode, respectively. However, seawater is preferred because it is the most abundant water resource. Although many R&D efforts on seawater electrolysis have been carried out since the 1970s, the barriers are the undesired chlorine gas evolution reaction at the anode, and corrosion induced by chloride ions. Unlike the available data for electrocatalyst materials based upon platinum group metals in pure solutions, limited data is available for electrocatalysts in seawater. Therefore, there is an urgent need to develop new electrocatalysts for seawater electrolysis.     

Characterization of bis-Schiff bases synthesized using ZnFe2O4 nanoparticles as catalyst,and examination of their antibacterial and in vitro cytotoxic properties

In this study, ZnFe₂O₄ nanoparticles (NPs) were prepared by a hydro/solvothermal method, and their structures were characterized by infrared, scanning electron microscopy, energy-dispersive X-ray spectroscopy and X-ray diffraction analyses. These ZnFe₂O₄ NPs were used in the synthesis of new bis-Schiff bases by condensation of hydroxyl-substituted aldehydes with various aromatic diamines in aqueous media. The antimicrobial activities of the synthesized bis-Schiff bases were tested against gram-negative as well as gram-positive bacteria. The MTT method was used to assess the anticancer activity of the bis-Schiff bases towards human lung and breast cancer cell lines. The results indicated that these compounds could be considered as new anti-tumor candidates.     

Electrochemical Sensing of Uric Acid Using a ZnO/Graphene Nanocomposite Modified Graphite Screen Printed Electrode

Russian Journal of Electrochemistry - An electrochemical sensor has been fabricated using ZnO/GR nanocomposite for selective determination of uric acid (UA) in a phosphate buffer solution (PBS, pH...     

Controlled and scalable torsional actuation of twisted nylon 6 fiber

Large‐scale torsional actuation occurs in twisted fibers and yarns as a result of volume change induced electrochemically, thermally, photonically, and other means. A quantitative relationship between torsional actuation (stroke and torque) and volume change is here introduced. The analysis is based on experimental investigation of the effects of fiber diameter and inserted twist on the torsional stroke and torque measured when heating and cooling nylon 6 fibers over the temperature range of 26–62 °C. The results show that the torsional stroke depends only on the amount of twist inserted into the fiber and is independent of fiber diameter. The torque generated is larger in fibers with more inserted twist and with larger diameters. These results are successfully modeled using a single‐helix approximation of the twisted fiber structure. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 1278–1286     

The 3F Library: Fluorinated Fsp3‐Rich Fragments for Expeditious 19F NMR Based Screening

Fragment‐based drug discovery (FBDD) is a popular method in academia and the pharmaceutical industry for the discovery of early lead candidates. Despite its wide‐spread use, the approach still suffers from laborious screening workflows and a limited diversity in the fragments applied. Presented here is the design, synthesis, and biological evaluation of the first fragment library specifically tailored to tackle both these challenges. The 3F library of 115 fluorinated, Fsp³‐rich fragments is shape diverse and natural‐product‐like with desirable physicochemical properties. The library is perfectly suited for rapid and efficient screening by NMR spectroscopy in a two‐stage workflow of ¹⁹F NMR and subsequent ¹H NMR methods. Hits against four diverse protein targets are widely distributed among the fragment scaffolds in the 3F library and a 67 % validation rate was achieved using secondary assays. This collection is the first synthetic fragment library tailor‐made for ¹⁹F NMR screening and the results demonstrate that the approach should find broad application in the FBDD community.