Boronic acids facilitate rapid oxime condensations at neutral pH

We report here the discovery and development of boron-assisted oxime formation as a powerful connective reaction for chemical biology. Oximes proximal to boronic acids form in neutral aqueous buffer with rate constants of more than 10⁴ M^–1 s^–1, the largest to date for any oxime condensation. Boron''s dynamic coordination chemistry confers an adaptability that seems to aid a number of elementary steps in the oxime condensation. In addition to applications in bioconjugation, the emerging importance of boronic acids in chemical biology as carbohydrate receptors or peroxide probes, and the growing list of drugs and drug candidates containing boronic acids suggest many potential applications.     

The Synthesis of Viridamine,A Penicillium Viridicatum Mycotoxin

The synthesis of viridamine, involving the condensation of 2-(3,3-dimethylallyi)-4(5)-formylimidazole with cyclo-glycyl-L-valyl is described. Different methods for the preparation of the imidazole intermediate were investigated.     

Synthesis of bis-8-hydroxyquinolines via an imination or a Suzuki-Miyaura coupling approach

Bis-8-hydroxyquinolines represent an important yet underexplored class of potential ligands for the preparation of various coordination polymers, which can be used in a plethora of applications. In this work, the synthesis of two types of bis-8-hydroxyquinolines, prepared via either an imination or a Suzuki-Miyaura coupling approach, as well as their analysis is discussed. Imination was pursued through the condensation of quinolinecarbaldehydes with diamines or aminoquinolines with dialdehydes, and the Suzuki-Miyaura coupling reactions were evaluated using a bromoquinoline substrate and diboronic acids.     

The Chiral Synthesis of Thiazole Amino Acid Enantiomers

An efficient modified Hantzsch reaction is described for the synthesis of optically pure thiazole amino acid derivatives from the corresponding amino acids. The method is exemplified by the synthesis of a derivative of L-(Gln)Thz, the novel chiral thiazole amino acid moiety of dolastatin 3. The Cotton effects of thiazole amino acids correlate well with the absolute stereochemistry of these compounds.     

Molecular and supramolecular dynamics of hybrid organic-inorganic interfaces for the rational construction of advanced hybrid nanomaterials

Today the capability to rationally design and construct hybrid materials utilizing a performance-property driven methodology is strongly dependent on our ability to control the structure and the dynamics of hybrid interfaces. This control needs a deep knowledge of their molecular and supramolecular dynamics that must be evaluated in situ, in the soft matter or colloidal states. For this purpose the use of modern methodologies of characterization such as time resolved synchrotron experiments and advanced pulsed field gradient NMR methods (DOSY) is particularly relevant. In this critical review, two important examples are discussed. They concern, first, the study of surface capping organic components' affinity towards nanoparticle surfaces by DOSY NMR. The knowledge and therefore the tuning of this affinity is paramount because it controls solubility, transferability and stability of colloidal dispersions of nanoparticles (NPs). In the second part, the mechanism of micellar templated formation of hybrid mesophases will be discussed in the frame of the main results obtained via in situ SAXS (107 references).     

Synthesis and Properties of Alkoxy‐ and Alkenyl‐Substituted Peralkylated Imidazolium Ionic Liquids

Novel peralkylated imidazolium ionic liquids bearing alkoxy and/or alkenyl side chains have been synthesized and studied. Different synthetic routes towards the imidazoles and the ionic liquids comprising bromide, iodide, methanesulfonate, bis(trifluoromethylsulfonyl)imide ([NTf₂]^?), and dicyanamide {[N(CN)₂]^?} as the anion were evaluated, and this led to a library of analogues, for which the melting points, viscosities, and electrochemical windows were determined. Incorporation of alkenyl moieties hindered solidification, except for cations with high symmetry. The alkoxy‐derivatized ionic liquids are often crystalline; however, room‐temperature ionic liquids (RTILs) were obtained with the weakly coordinating anions [NTf₂]^? and [N(CN)₂]^?. For the viscosities of the peralkylated RTILs, an opposite trend was found, that is, the alkoxy derivatives are less viscous than their alkenyl‐substituted analogues. Of the crystalline compounds, X‐ray diffraction data were recorded and related to their molecular properties. Upon alkoxy substitution, the electrochemical cathodic limit potential was found to be more positive, whereas the complete electrochemical window of the alkenyl‐substituted imidazolium salts was shifted to somewhat more positive potentials.     

Experimental study of the influence of low frequency flow modulation on the whistling behavior of a corrugated pipe

It is well known that airflow in a corrugated pipe can excite whistling at the frequencies of the pipe's longitudinal acoustic modes. This short contribution reports on the results of experiments where a low frequency, oscillating flow with velocity magnitudes of the same order as the airflow has been added. Depending on the oscillation strength, it has been found that this flow may silence the pipe or move the whistling to higher harmonics. It is also shown that the low frequency oscillation itself may excite higher frequency whistling sounds in the pipe.     

Highly phosphorescent perfect green emitting iridium(iii) complex for application in OLEDs

A novel iridium complex, [bis-(2-phenylpyridine)(2-carboxy-4-dimethylaminopyridine)iridium(iii)] (N984), was synthesized and characterized using spectroscopic and electrochemical methods; a solution processable OLED device incorporating the N984 complex displays electroluminescence spectra with a narrow bandwidth of 70 nm at half of its intensity, with colour coordinates of x = 0.322; y = 0.529 that are very close to those suggested by the PAL standard for a green emitter.     

Grazing incident small angle x-ray scattering study of polymer thin films with embedded ordered nanometer cells

Analysis of nanostructures is of increasing importance with advances of nanotechnology. Embedded nanostructures in thin films in particular are of recent interest. Grazing incident small angle x-ray scattering (GISAXS) has been recognized to be a powerful method to probe such embedded nanostructures; however, quantitative analysis of scattering pattern is not always trivial due to complex refraction and reflection at surface and interfaces. We prepared nanocellular thin films using block copolymer template with carbon dioxide (CO(2)); CO(2) "bubbles" were formed in the CO(2)-philic block domains. Such nanocellular structures were analyzed by GISAXS and simulated using distorted wave Born approximation (DWBA). Unlike traditional transmission x-ray scattering, GISAXS requires a careful choice of incident angle to analyze the form factor of scatters embedded in a thin film. Nevertheless, the GISAXS measurements under optimized geometry with quantitative calculations using DWBA revealed that the nanocells are spherical and aligned in a single layer of hexagonal lattice and are surrounded by CO(2)-philic block domains.     

On-line solid-phase extraction with on-support derivatization for high-sensitivity liquid chromatography tandem mass spectrometry of estrogens in influent/effluent of wastewater treatment plants

A solid-phase extraction coupled to liquid chromatography/tandem mass spectrometry for the determination of estrogens in sewage influent and effluent has been performed. The possibility of preparing estrogen derivatives directly on a solid-phase extraction bed in which the targeted analytes have been previously isolated and pre-concentrated was explored. This method uses an Oasis HLB column (2.1 mm x 20 mm i.d.) for on-line sample cleanup and derivatization support, and a Sunfire C(18) column (150 mm x 2.1 mm i.d.) with a mobile phase consisting of acetonitrile-water-formic acid for separation. After sample introduction, some matrix interferences are removed by washing up SPE column with methanol-water. Phenolic hydroxyl group of estrogens is subsequently derivatized with dansyl chloride. Reaction takes place in the on-line solid-phase extraction column. The excess of reagent and other matrix interferences are then removed by a second washing. Dansylated estrogens are further back eluted and analyzed with HPLC-MS-MS. The optimized on-line protocol is emphasized owing to a low limit of quantification (1 ng L(-1)) is achieved with only around 1 mL of sample and a low sensitive MS instrument. Developed strategy has been demonstrated to be an improvement over existing methods due to its greater sensitivity and the low volume of matrix used and the total analysis time (extraction, derivatization, analysis) is less than 17 min.