Electrodeposited paint-and-varnish nickel–polymer coatings

Specific features of preparation of paint-and-varnish nickel–polymer coatings by joint cathodic electrodeposition of an amine-containing oligomeric electrolyte and nickel were studied. The coatings obtained exhibit layer-by-layer heterogeneity, with the lowest layer constituted by an intermetallic compound of nickel with iron. The coatings are characterized by higher degree of cross-linking compared to the polymer coatings without nickel. A paint-and-varnish formulation based on a nickel–polymer film-forming agent was developed for electrodeposition of corrosion- and wear-resistant coatings.     

Identification of hydroxymethylpyrazines using mass spectrometry

Pyrazines are well‐known natural products that are present in bacterial odours and food flavouring agents and are used as insect pheromones. Recently, a number of hydroxymethylpyrazines have been identified as thynnine wasp pheromones and orchid semiochemicals that are essential for pollination in sexually deceptive plants. These compounds are present in low amounts in complex blends, making GC–MS (including high‐resolution techniques) the method of choice for their structure elucidation. We report the EI mass spectra for 14 representative compounds and have found that based on characteristic fragmentations, it is possible to distinguish between different positional isomers of hydroxymethylpyrazines. The presence or absence of either [M ? 17]⁺, [M ? 18]^+· or [M ? 19]⁺ fragment species provides characteristic information to allow the distinction between the different isomers. Considering the importance of pyrazines as a group of bioactive natural products, and the recent findings of biological activity for hydroxymethylpyrazines, our results presented here will aid the identification of these compounds in other biological systems. Copyright © 2015 John Wiley & Sons, Ltd.     

Cooperative Lewis Pairs Based on Late Transition Metals: Activation of Small Molecules by Platinum(0) and B(C6F5)3

A Lewis basic platinum(0)–CO complex supported by a diphosphine ligand and B(C₆F₅)₃ act cooperatively, in a manner reminiscent of a frustrated Lewis pair, to activate small molecules such as hydrogen, CO₂, and ethene. This cooperative Lewis pair facilitates the coupling of CO and ethene in a new way.     

Acceleration of Acetal Hydrolysis by Remote Alkoxy Groups: Evidence for Electrostatic Effects on the Formation of Oxocarbenium Ions

In contrast to observations with carbohydrates, experiments with 4‐alkoxy‐substituted acetals indicate that an alkoxy group can accelerate acetal hydrolysis by up to 20‐fold compared to substrates without an alkoxy group. The acceleration of ionization in more flexible acetals can be up to 200‐fold when compensated for inductive effects.     

Structural Characterization of O‐ and C‐Glycosylating Variants of the Landomycin Glycosyltransferase LanGT2

The structures of the O‐glycosyltransferase LanGT2 and the engineered, C? C bond‐forming variant LanGT2S8Ac show how the replacement of a single loop can change the functionality of the enzyme. Crystal structures of the enzymes in complex with a nonhydrolyzable nucleotide‐sugar analogue revealed that there is a conformational transition to create the binding sites for the aglycon substrate. This induced‐fit transition was explored by molecular docking experiments with various aglycon substrates.     

Metal‐Catalyzed “On‐Demand” Production of Carbonyl Sulfide from Carbon Monoxide and Elemental Sulfur

The group 6 molybdenum(II) cyclopentadienyl amidinate (CPAM) bis(carbonyl) complex [Cp*Mo{N(iPr)C(Ph)N(iPr)}(CO)₂] (Cp*=η⁵‐C₅Me₅) serves as a precatalyst for the high‐yielding photocatalytic production of COS from CO and S₈ under near‐ambient conditions (e.g., 10 psi, 25 °C). Further documented is the isolation and structural characterization of several key transition‐metal intermediates which collectively support a novel molybdenum(IV)‐based catalytic cycle as being operative. Finally, in the presence of an excess amount of a primary amine, it is demonstrated that this catalytic system can be successfully used for the “on‐demand” generation and utilization of COS as a chemical reagent for the synthesis of ureas.     

Direct Catalytic Enantio‐ and Diastereoselective Ketone Aldol Reactions of Isocyanoacetates

A catalytic asymmetric aldol addition/cyclization reaction of unactivated ketones with isocyanoacetate pronucleophiles has been developed. A quinine‐derived aminophosphine precatalyst and silver oxide were found to be an effective binary catalyst system and promoted the reaction to afford chiral oxazolines possessing a fully substituted stereocenter with good diastereoselectivities and excellent enantioselectivities.     

Synthesis of potential inhibitors of glycosyltransferases representing UDP-GlcNAc

Based on rational design of the transition state analog inhibitors of glycosyltransferases, four model glycomimetics of this type, viz. benzyl 2-thio-α-dfructofuranoside 1-diethylphosphate (XIa), its β-anomer (XIb), and their ethyl 2-thio analogs — α-anomer (XIIa) and β-anomer (XIIb), were synthesized. In addition, fourteen precursors arising during the synthesis of the desired final model compounds (XI and XII), partially or fully acetylated benzyl and/or ethyl 2-thiofructofuranoside 1-diethyl phosphates, were isolated and characterized with the aim to prepare complete series of glycomimetics, representing donor UDP-GlcNAc designated for biological assays on human GnT’s, viz. GnT-I, Core2GnT, and GnT-V.     

Synthesis and characterization of nano Ag end capped L-cysteine bridged diblock copolymer

The target of the present investigation is synthesis and characterization of an amphiphilic diblock copolymer with antibacterial property. Ring opening polymerization (ROP) of ε-caprolactone (CL) and tetrahydrofuran (THF) was carried out under inert atmosphere by using L-cysteine as a bridging agent in the presence of stannous octoate (SO) as a catalyst. The nano silver end capped diblock copolymer was synthesized by in situ method. Thus obtained nano silver end capped L-cysteine bridged diblock copolymer was characterized by various analytical methods like Fourier transform infrared (FTIR) spectroscopy, nuclear magnetic resonance (NMR) spectroscopy, circular dichroism (CD), fluorescence spectroscopy, gel permeation chromatography (GPC), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), field emission scanning electron microscopy (FESEM), high resolution transmission electron microscopy (HRTEM) and zeta potential. The antimicrobial property of the nano silver end capped diblock copolymer against e-coli was tested.