A new approach to the spectral study of unstable radicals and ions in solution by the use of an inert gas glovebox system: observation and analysis of the infrared spectra of the radical anion and dianion of p-terphenyl

By using a Fourier-transform infrared spectrometer contained in an inert gas glovebox system (oxygen and water concentrations: <0.1 ppm), high-quality infrared absorption spectra have been observed for the radical anion and dianion of p-terphenyl in tetrahydrofuran solutions. Density functional theory with the B3LYP nonlocal exchange-correlation functional and the 6-311+G** basis set has been used for the calculations of the structures and infrared spectra of the neutral species, radical anion, and dianion of p-terphenyl. The observed infrared spectra of the radical anion and dianion are in good agreement with those calculated by density functional theory. The origin of the strong infrared absorption intensities characteristic of the radical anion and dianion are discussed in terms of changes in electronic structures induced by specific normal vibrations (electron-molecular vibration interaction).     

Electrocatalytic oxidation of alcohols by a carbon-supported Rh porphyrin

A Rh porphyrin on carbon black was shown to catalyze the electro-oxidation of several aliphatic alcohols (ethanol, 1-propanol, and 2-propanol) and benzyl alcohols. The overpotentials for alcohol oxidation were very low. The reaction mechanism and substrate specificity are discussed.     

Electroreductive five- and six-membered cyclization of aromatic β- and γ-imino esters derived from (S)-aspartic acid and (S)-glutamic acid

The electroreduction of aromatic β-dimethylcarbamoyl-β-imino esters, prepared from (S)-aspartic acid, in the presence of chlorotrimethylsilane gave five-membered cyclized products, 1-benzoyl-4-hydroxy-5-aryl-N,N-dimethylpyrrolidine-2-carboxamides and 5-(dimethylcarbamoyl)-2-aryl-1H-pyrrol-3-yl benzoates, depending on the post-treatment after the electroreduction. The electroreduction of aromatic γ-dialkylcarbamoyl-γ-imino and γ-methoxylmethyl-γ-imino esters, prepared from (S)-glutamic acid, and following transformation gave six-membered cyclized products, 1-benzoyl-5-hydroxy-N,N-dialkyl-6-phenylpiperidine-2-carboxamides and 3-hydroxy-6-(methoxymethyl)-2-phenylpiperidin-1-yl)(phenyl)methanones, respectively.     

Polynomial invariants and quandles of twisted links

Bourgoin defined the notion of a twisted link which corresponds to a stable equivalence class of links in oriented thickenings. It is a generalization of a virtual link. Some invariants of virtual links are extended for twisted links including the knot group and the Jones polynomial. In this paper, we generalize a multivariable polynomial invariant of a virtual link to a twisted link. We also introduce a quandle of a twisted link.     

A facile and clean direct cyanation of heteroaromatic compounds using a recyclable hypervalent iodine(III) reagent

The facile and clean direct cyanating reaction of pyrroles and thiophenes has been achieved using a recyclable hypervalent iodine(III) reagent 1b by a simple solid-liquid separation of the products and the reagent.     

Imaging mass spectrometry with silver naeoparticles reveals the distribution of fatty acids in mouse retinal sections

A new approach to the visualization of fatty acids in mouse liver and retinal samples has been developed using silver nanoparticles (AgNPs) in nanoparticle-assisted laser desorption/ ionization imaging mass spectrometry (nano-PALDI-IMS) in negative ion mode. So far, IMS analysis has concentrated on main cell components, such as cell membrane phospholipids and cytoskeletal peptides. AgNPs modified with alkylcarboxylate and alkylamine were used for nano-PALDI-IMS to identify fatty acids, such as stearic, oleic, linoleic, arachidonic, and eicosapentaenoic acids, as well as palmitic acid, in mouse liver sections; these fatty acids are not detected using 2,5-dihydroxybenzoic acid (DHB) as a matrix. The limit of detection for the determination of palmitic acid was 50 pmol using nano-PALDI-IMS. The nano-PALDI-IMS method is successfully applied to the reconstruction of the ion images of fatty acids in mouse liver sections. We verified the detection of fatty acids in liver tissue sections of mice by analyzing standard lipid samples, which showed that fatty acids were from free fatty acids and dissociated fatty acids from lipids when irradiated with a laser. Additionally, we applied the proposed method to the identification of fatty acids in mouse retinal tissue sections, which enabled us to learn the six-zonal distribution of fatty acids in different layers of the retina. We believe that the current approach using AgNPs in nano-PALDI-IMS could lead to a new strategy to analyze basic biological mechanisms and several diseases through the distribution of fatty acids.     

Amycolamicin: A Novel Broad‐Spectrum Antibiotic Inhibiting Bacterial Topoisomerase

The abuse of antibacterial drugs imposes a selection pressure on bacteria that has driven the evolution of multidrug resistance in many pathogens. Our efforts to discover novel classes of antibiotics to combat these pathogens resulted in the discovery of amycolamicin (AMM). The absolute structure of AMM was determined by NMR spectroscopy, X‐ray analysis, chemical degradation, and modification of its functional groups. AMM consists of trans‐decalin, tetramic acid, two unusual sugars (amycolose and amykitanose), and dichloropyrrole carboxylic acid. The pyranose ring named as amykitanose undergoes anomerization in methanol. AMM is a potent and broad‐spectrum antibiotic against Gram‐positive pathogenic bacteria by inhibiting DNA gyrase and bacterial topoisomerase IV. The target of AMM has been proved to be the DNA gyrase B subunit and its binding mode to DNA gyrase is different from those of novobiocin and coumermycin, the known DNA gyrase inhibitors.     

Molecular Recognition by Cyclophane/Guanidinium Supramolecular Receptor Embedded at the Air-Water Interface

In order to develop a supramolecular receptor through a self-assembling process, a site-specific host and an inclusion-type host were mixed as a Langmuir monolayer, and guest binding and pressure-induced fluorescence emission were investigated. A guanidinium amphiphile and several cyclophanes carrying hydrophobic moieties were used as the host molecules; molecular recognition of an aqueous fluorescent guest, 6-p-toluidino-2-naphthalenesulfonic acid (TNS) by binary mixed receptor monolayers was evaluated by a surface pressure-molecular area (π-A) isotherm and a surface fluorescence measurement. An apparent increase in fluorescence intensity was observed when the mixed monolayers of the guanidinium and cyclophane amphiphiles were compressed on an aqueous TNS solution. In contrast, single-component monolayers of the guanidinium or the cyclophane did not show a significant increase in fluorescence emission. In the mixed monolayers, the guest TNS would be bound to the interface by strong electrostatic interaction with the guanidinium, and inclusion of the formed complex probably suppresses the quenching effect in polar medium and/or self-quenching. Experiments with various mixing ratios of these components suggest selective formation of an equimolar cooperative receptor of the guanidinium and the cyclophane. Investigation of the cyclophane structures by fluorescence emission and a competitive binding experiment with another guest were also carried out.