Asymmetric intermolecular Pauson-Khand reactions of unstrained olefins: the (o-dimethylamino)phenylsulfinyl group as an efficient chiral auxiliary

The first asymmetric version of intermolecular Pauson-Khand reactions of unstrained alkenes is described. Generally simple acyclic alkenes exhibit low reactivity and regioselectivity in intermolecular Pauson-Khand reactions; however, o-(dimethylamino)phenyl vinyl sulfoxide reacts under very mild conditions with a wide variety of terminal alkynes in a completely regioselective and highly stereoselective manner. The utility of the resulting 5-sulfinyl-2-cyclopentenones in asymmetric synthesis is illustrated by a very short enantioselective synthesis of the antibiotic (-)-pentenomycin I.     

The mass spectrometric study on aminohydroxamic acids‐based metallacrowns

Electrospray ionization mass spectrometry (MS) has been widely used to detect noncovalent interactions in supramolecular compounds, especially in biological systems. In our work, we present the application of the electrospray ionization MS technique to characterize the metallamacrocycles, known as metallacrowns. This project involves investigations of the aminohydroxamic acids structure and chirality influence on formation of ternary 12‐metallacrown‐4 complexes. For our experiments, we used a series of β‐aminohydroxamic acids and derivatives of histidinehydroxamic acid. A high stability of the studied supramolecular systems in the gas phase was confirmed by MS/MS experiments. We also proposed the fragmentation pathways for the studied compounds. Obtained results reveal that the ternary 12‐metallacrown‐4 formation process is not selective, and ligands of various structures and chiralities can be incorporated into these systems. Copyright © 2014 John Wiley & Sons, Ltd.     

hcp‐Co Nanowires Grown on Metallic Foams as Catalysts for Fischer–Tropsch Synthesis

The Fischer–Tropsch synthesis (FTS) is a structure‐sensitive exothermic reaction that enables catalytic transformation of syngas to high quality liquid fuels. Now, monolithic cobalt‐based heterogeneous catalysts were elaborated through a wet chemistry approach that allows control over nanocrystal shape and crystallographic phase, while at the same time enables heat management. Copper and nickel foams have been employed as supports for the epitaxial growth of hcp‐Co nanowires directly from a solution containing a coordination compound of cobalt and stabilizing ligands. The Co/Cu_foam catalyst was tested for Fischer–Tropsch synthesis in a fixed‐bed reactor, showing stability and significantly superior activity and selectivity towards C5+ compared to a Co/SiO₂‐Al₂O₃ reference catalyst under the same conditions.     

Thermal and physical properties of ZrO2–AlO(OH) nanopowders synthesised by microwave hydrothermal method

Journal of Thermal Analysis and Calorimetry - Industrially relevant nanopowder was synthesised by microwave hydrothermal synthesis to obtain well-controlled composition (ZrO2–AlO(OH) system)...     

Thermal and spectral analysis of copolymers with sulphur groups

Journal of Thermal Analysis and Calorimetry - The paper presents the synthesis, structure and polymerization of S-phenyl 2-methylprop-2-enethioate (PSM). This compound was prepared in the reaction...     

Njaoamine I,a cytotoxic polycyclic alkaloid from the Haplosclerida sponge Haliclona (Reniera) sp.

A new cytotoxic polycyclic alkaloid containing a quinoline moiety, njaoamine I (1) has been isolated from the methanol extract of the sponge Haliclona (Reniera) sp. collected at Okuza Island, Tanzania. The structure of compound 1 was determined by 1D and 2D NMR and HRMS data analysis. Its relative configuration was elucidated by a NOESY experiment and confirmed by comparison of its NMR spectral data to those of njaoamines A–H. Moreover, njaoamine G (2) was also detected by LC/MS analysis of the methanol extract. Njaoamine I (1) displays cytotoxic activity against a panel of three human tumor cell lines in the micromolar range.     

Influence of constant magnetic field on electrodeposition of metals,alloys, conductive polymers,and organic reactions

The paper presents and summarizes some research on constant magnetic field effects in chemistry. Metals and alloys electrodeposited under constant magnetic field have greater thickness and smoother surface with finest grains. Metallic materials deposited under the influence of uniform magnetic field may have stronger corrosion resistance, than those obtained without the presence of magnetic field. Constant magnetic field also causes an increase of the electropolymerization rate and yield of some organic reactions. Our research also shows that the presence of constant magnetic field affects the electrodeposition process of alloys and their morphology to a great extent. The effects of magnetic field on metals, alloys, composites, polymers and other materials are due to the Lorentz force and the magnetohydrodynamic effect. It is possible that the further development of magnetoelectrodeposition will allow for using the constant magnetic field to improve the properties of metal coatings, alloys, polymers, and other materials in the industry.     

Enantioselective approach to indolizidine and quinolizidine scaffolds. Application to the synthesis of peptide mimics

An enantioselective approach to substituted indolizidine and quinolizidine frameworks has been developed. Key steps of the synthesis are the enantioselective, palladium-catalyzed N-allylation of an imide, the nucleophilic allylation of an acyliminium ion and a ring closing metathesis. This general strategy has been applied to the synthesis of indolizidine peptide mimics, starting from a chiral imide derived from l-aspartic acid. It was observed that the preexisting stereogenic center of this substrate has a moderate influence on the stereoselectivity of the electrophilic allylation, which is mainly determined by the sense of chirality of the catalyst.     

The structure of fosfomycin salts in solution and in the solid state by nuclear magnetic resonance spectroscopy and DFT calculations

Two samples of fosfomycin salts, the calcium and the disodium ones, were used to record their NMR spectra both in solution and in the solid state. The existence of fosfomycin in a neutral and two ionized structures (mono and dianion) was considered to interpret the spectra that were solved using the GIAO calculated chemical shifts of the minimum energy conformations. Although the starting materials were dianions, the spectra in solution show the presence of monoanions.     

Conformational search and spectroscopic analysis of bis-β-d-glucopyranosyl azacrown derivative

1,10-N,N′-bis-(β-d-ureidoglucopyranosyl)-4,7,13-trioxa-1,10-diazacyclopentadecane is a new, recently synthesized compound, which exhibits complexation ability towards drugs. In the present study various theoretical methods, including molecular mechanics, computer simulations, semiempirical and DFT calculations, are applied to find the lowest energy conformers of this molecule in vacuo and in aqueous solution. For the most stable structures the vibrational frequencies as well as the C and H chemical shifts were computed. Along with the theoretical investigation the IR in the KBr discs and the NMR spectra in water and in pyridine were experimentally recorded. It is shown that in the lowest energy structures the two glucosyl units are placed on the same side of the diazacrown ring with their mutual orientations favoring formation of hydrogen bonds. The “open” structure, in which no such hydrogen bonds can be formed, is found to have much higher energy. The computed and measured IR spectra and NMR chemical shifts are compared and discussed in detail. The most stable structures are analyzed with respect to the possible mechanism of complexation of drugs.