A novel flame retardant containing phosphorus,nitrogen, and sulfur

In this article, a novel intumescent flame retardant (IFR) PNSFR containing three flame-retardant elements, phosphorus, nitrogen, and sulfur was designed and synthesized. Then a series of flame-retardant thermoplastic polyurethanes (TPU) were prepared using the PNSFR. The effects of the flame retardant on the flammability of TPU/PNSFR composites were investigated by limited oxygen index (LOI) and UL-94 vertical burning. The results showed that TPU containing 10 mass% PNSFR had the highest LOI value (36) and could reach the V-0 rating. The flame-retardant mechanism of PNSFR in TPU was also disclosed using thermogravimetric analysis (TG), scanning electron micrograph, TG-infared spectrometry, and Fourier transform infrared spectroscopy. The sulfur and phosphorus elements of PNSFR can be kept in residual char. Moreover, an optimal loading amount of the IFR in TPU is in favor of forming dense and continuous char layer to prevent heat transfer and the spread of flammable gases. The IFR PNSFR may find potential use for various flame-retardant polyurethanes.     

Substrate‐Dependent H/D Kinetic Isotope Effects and the Role of the Di(μ‐oxo)diiron(IV) Core in Soluble Methane Monooxygenase: A Theoretical Study

Soluble methane monooxygenase (sMMO) is an enzyme that converts alkanes to alcohols using a di(μ‐oxo)diiron(IV) intermediate Q at the active site. Very large kinetic isotope effects (KIEs) indicative of significant tunneling are observed for the hydrogen transfer (H‐transfer) of CH₄ and CH₃CN; however, a relatively small KIE is observed for CH₃NO₂. The detailed mechanism of the enzymatic H‐transfer responsible for the diverse range of KIEs is not yet fully understood. In this study, variational transition‐state theory including the multidimensional tunneling approximation is used to calculate rate constants to predict KIEs based on the quantum‐mechanically generated intrinsic reaction coordinates of the H‐transfer by the di(μ‐oxo)diiron(IV) complex. The results of our study reveal that the role of the di(μ‐oxo)diiron(IV) core and the H‐transfer mechanism are dependent on the substrate. For CH₄, substrate binding induces an electron transfer from the oxygen to one Fe^IV center, which in turn makes the μ‐O ligand more electrophilic and assists the H‐transfer by abstracting an electron from the C?H σ orbital. For CH₃CN, the reduction of Fe^IV to Fe^III occurs gradually with substrate binding and H‐transfer. The charge density and electrophilicity of the μ‐O ligand hardly change upon substrate binding; however, for CH₃NO₂, there seems to be no electron movement from μ‐O to Fe^IV during the H‐transfer. Thus, the μ‐O ligand appears to abstract a proton without an electron from the C?H σ orbital. The calculated KIEs for CH₄, CH₃CN, and CH₃NO₂ are 24.4, 49.0, and 8.27, respectively, at 293 K, in remarkably good agreement with the experimental values. This study reveals that diverse KIE values originate mainly from tunneling to the same di(μ‐oxo)diiron(IV) core for all substrates, and demonstrate that the reaction dynamics are essential for reproducing experimental results and understanding the role of the diiron core for methane oxidation in sMMO.     

A2E‐Mediated Photochemical Modification to Fibronectin and its Implications to Age‐Related Changes in Bruch's Membrane

Lipofuscin accumulates normally with age and is more pronounced in retinal dystrophies such as age‐related macular degeneration. The major bis‐retinoid component of lipofuscin is A2E. In addition to cell damage effects by A2E, we have previously demonstrated that blue‐light–mediated A2E leads to modifications in the basement membrane protein laminin. Therefore, the purpose of this study was to advance the understanding of A2E photooxidation effects on fibronectin, the major glycoprotein of Bruch's membrane. In this study, A2E was irradiated with blue light in the presence of a fibronectin peptide consisting of amino acids from the integrin binding region. The modification sites were identified via LC/MS. Our research indicated that blue light irradiation caused cleavage throughout the A2E molecule closest to the pyridinium ring, and attached to the fibronectin peptide preferentially at lysine and arginine residues. All of these reactions are similar to the Maillard reaction. Altogether this study suggests that blue‐light–irradiated A2E modifies peptides and forms advance glycation endproducts. Furthermore, these results can be used to identify modifications that occur in Bruch's membrane in vivo.     

Synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives

Different approaches for the synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives from simple amino acids have been investigated. A library of 33 precursors for the preparation of N-hydroxy pyrazinones was obtained in moderate to good yields.     

Imino ene-type reaction of enamines with N-sulfonylimines and application to diastereoselective synthesis of N-sulfonyl-1,3-diamines

Enamines react rapidly with N-sulfonylimines to afford imino ene-type adducts. The reaction proceeds even at −78 °C in the presence of acetic acid and shows high diastereoselectivity. Acid hydrolysis of imino ene-type products affords β-amino ketones, and reduction with NaBH₃CN furnishes N-sulfonyl-1,3-diamines with high diastereoselectivities. The stereochemistry of these transformations is considered based on transition state models.     

自由基加成/关环反应合成1,3-二氢吲哚-2-酮的研究进展

近两年来,关于自由基加成/关环反应合成1,3-二氢吲哚-2-酮的报道屡见不鲜.它们大多以N-芳基取代的丙烯酰胺类化合物为底物,在各种不同的金属、无金属和光的催化作用下,与不同的自由基反应,可以一步生成3,3-二取代的吲哚-2-酮衍生物.该类方法现已成为合成含氮五元杂环的一个重要手段,用来合成1,3-二氢吲哚-2-酮及其衍生物.目前对自由基加成/关环反应合成该类化合物的研究多集中在不同催化手段引发不同的自由基和反应机理上.按催化剂类型的不同,对近年来自由基加成/关环反应合成吲哚-2-酮的研究进展进行了综述.     

Optimization and Evaluation of 5-Styryl-Oxathiazol-2-one Mycobacterium tuberculosis Proteasome Inhibitors as Potential Antitubercular Agents

This is the first report of 5-styryl-oxathiazol-2-ones as inhibitors of the Mycobacterium tuberculosis (Mtb) proteasome. As part of the study, the structure–activity relationship of oxathiazolones as Mtb proteasome inhibitors has been investigated. Furthermore, the prepared compounds displayed a good selectivity profile for Mtb compared to the human proteasome. The 5-styryl-oxathiazol-2-one inhibitors identified showed little activity against replicating Mtb, but were rapidly bactericidal against nonreplicating bacteria. (E)-5-(4-Chlorostyryl)-1,3,4-oxathiazol-2-one) was most effective, reducing the colony-forming units (CFU)/mL below the detection limit in only seven days at all concentrations tested. The results suggest that this new class of Mtb proteasome inhibitors has the potential to be further developed into novel antitubercular agents for synergistic combination therapies with existing drugs.     

Coupling‐Reagent‐Free Synthesis of Dipeptides and Tripeptides Using Amino Acid Ionic Liquids

A general method for the synthesis of dipeptides has been developed, which does not require any coupling reagents. This method is based on the reaction of readily available HCl salts of amino acid methyl esters with tetrabutylphosphonium amino acid ionic liquids. The isolation procedure of stepwise treatment with AcOH is easy to carry out. The method was extended to the synthesis of tripeptide, tyrosyl‐glycyl‐glycine, present in IMREG‐1, also.     

Waterborne polyurethane/NiAl‐LDH/ZnO composites with high antibacterial activity

Novel waterborne polyurethane (WPU) composites based on NiAl‐LDH and ZnO were successfully synthesized by in‐situ polymerization. The nanostructured NiAl‐LDH/ZnO was first grafted by isophorone diisocyanate (IPDI), forming the NiAl‐LDH/ZnO‐NCO complex with ―NCO group on the surface, which promotes its homogeneous dispersion in WPU matrix. The microstructure and particle distribution of the composites were characterized. The mechanical properties and the water resistance of the composites were improved. Furthermore, the composites also exhibit significant antibacterial activity towards G(?) Escherichia coli and G(+) Staphylococcus aureus. Copyright © 2015 John Wiley & Sons, Ltd.     

Oligo(ethylene oxide)-functionalized trialkoxysilanes as novel electrolytes for high-voltage lithium-ion batteries

Oligo(ethylene oxide)-functionalized trialkoxysilanes were synthesized through hydrosilylation reaction by reacting trialkoxysilane with oligo(ethylene oxide) allyl methyl ether using PtO₂ as a catalyst. The physical properties of these compounds, such as viscosity, dielectric constant, and ionic conductivity, were characterized. Among them, [3-(2-(2-methoxyethoxy)ethoxy)-propyl]triethoxysilane (TESM2) exhibited a commercial viable ionic conductivity of 1.14 mS cm^?1 and a wide electrochemical window of 5.2 V. A preliminary investigation was conducted by using TESM2 as an electrolyte solvent for high-voltage applications in lithium-ion batteries. Using 1 M LiPF₆ in TESM2 with 1 vol% vinyl carbonate as an electrolyte, LiCoO₂/Li half-cell delivered a specific capacity of 153.9 mAh g^?1 and 90 % capacity retention after 80 cycles (3.0–4.35 V, 28 mA g^?1); Li_1.2Ni_0.2Mn_0.6O₂/Li₄Ti₅O₁₂ full cell exhibited the initial capacity of 161.3 mAh g^?1 and 86 % capacity retention after 30 cycles (0.5–3.1 V, 18 mA g^?1).