Iodine(III)-mediated ethoxychlorination of enamides with iron(III) chloride

The combination of (diacetoxyiodo)benzene and iron(III) chloride in ethanol allows the efficient regioselective ethoxychlorination of a broad range of enamides. Mechanistic studies tend to rule out the involvement of free radical species and point towards the implication of a mixed [chloro(ethoxy)iodo]benzene intermediate.     

Cholesteric bonded stationary phases for high-performance liquid chromatography: synthesis, physicochemical characterization, and chromatographic behavior of a phospho–cholesteric bonded support. A new way to mimic drug/membrane interactions?

Among the various methods exploitable to determine the bioavailability of drugs, reversed-phase liquid chromatography (RPLC) appears to be suited to creation of patterns of prediction. In this context a new stationary phase was designed in this work to reproduce, in terms of chemical structure, as accurately as possible, the main elements of cellular membranes; which include phospholipids and cholesterol molecules. An efficient synthetic pathway was developed to prepare ligands that contain a phosphate head, a long alkyl chain chemically bonded to silica, and a cholesteric moiety, in order to mimic both hydrophilic and hydrophobic interactions, and "membrane-like" organization, respectively. The new stationary phase was characterized by Fourier-transform infra red (FTIR) and (1)H-(13)C, (1)H-(31)P, and (1)H-(29)Si cross-polarization magic-angle-spinning nuclear magnetic resonance (CP MAS NMR) spectroscopy. Its chromatographic behavior has been studied by classical classification tests for RPLC columns. Despite its low surface coverage, the material produced exhibits high shape selectivity, possibly due to the organization of the grafted moieties.     

Alkylammonium-based protic ionic liquids. II. Ionic transport and heat-transfer properties: fragility and ionicity rule

The physicochemical characterization of six alkylammonium-based protic ionic liquids (PILs) is presented. These compounds were prepared through a simple and atom-economic neutralization reaction between a tertiary amine and a Br?nsted acid, HX, where X- is HCOO-, CH3COO-, HF2-. The temperature dependency and the effect of added water on properties such as density, viscosity, ionic conductivity, and the thermal comportment of these PILs were measured and investigated. The results allowed us to classify them according to a classical Walden diagram and to appreciate their great "fragility". PILs have applicable perspectives in replacements of conventional inorganic acids for fuel cell devices and thermal transfer fluids.     

Analysis of high molecular mass proteins larger than 150 kDa using cyanogen bromide cleavage and conventional 2-DE

Proteomic approaches including high-resolution 2-DE are providing the tools needed to discover disease-associated biomarkers in complex biological samples. Although 2-DE is an extremely powerful approach to analyze the proteome, the separation of proteins with extreme molecular masses still remains an issue requiring improvement. Because high molecular mass (HMM) proteins larger than 150 kDa have already been observed to be differentially expressed in several pathologies such as cancer, we developed an original strategy to analyze this part of the proteome that is not easily separated by 2-DE in polyacrylamide gels. This strategy is based on the 2-DE separation of cyanogen bromide (CNBr) fragments of purified HMM protein fractions, and combines techniques including SEC fractionation, TCA precipitation, CNBr cleavage, 2-DE and MS analysis. The method was first tested on a model protein, the BSA. Preliminary results obtained using colonic tissues led to the identification of six HMM proteins with M(r) comprised between 163 and 533 kDa in their reduced state. These results demonstrated that our CNBr/2-DE approach should provide a powerful tool for identification of new biomarkers larger than 150 kDa.     

Online large volume sample staking preconcentration and separation of enantiomeric GHRH analogs by capillary electrophoresis

A capillary electrophoresis method is proposed to analyze the four most well-known growth hormone–releasing hormone (GHRH) analogs that are misused by athletes. Dimethyl-β-cyclodextrin used as a chiral selector allowed, for the first time, the separation of those basic peptide analogs, including enantiopeptides (sermorelin and CJC-1293) that differ by the chirality of only one amino acid. To increase the method sensitivity, electrokinetic preconcentration methods have been investigated. The large volume sample stacking with polarity switching (PS-LVSS) method with an injected sample volume corresponding to 80% of the capillary one was found superior to the sweeping in terms of signal enhancement factor (SEF). Acid and organic solvent addition to the sample (0.1 mM phosphoric acid with 30% methanol) led to a twofold signal improvement, when compared to water as a matrix. We increased capillary dimensions to provide a signal enhancement through the injection of a larger sample volume. Finally, using a combination of the optimized PS-LVSS preconcentration with the chiral capillary zone electrophoresis (CZE), the GHRH analogs were separated and limits of detection between 75 and 200 ng/mL were reached. This method was successfully applied to urine after a desalting step. An optimized C18 SPE was used for that purpose in order to provide low sample conductivity (<130 µS/cm) and preserve the efficiency of LVSS preconcentration. SEF of 640 was obtained with desalted urine spiked with sermorelin by comparison to the CZE (without preconcentration) method.     

Design of oxide nanoparticles by aqueous chemistry

The elaboration of nanoparticles designed for technological applications in various fields such as catalysis, optics, magnetism, electronics… needs the strict control of their characteristics, especially chemical composition, crystalline structure, size, and shape. These characteristics bring the physical properties (color, magnetism, band gap…) of the material, and also the surface to volume ratio of particles which is of high importance when they are used as a chemically active or reactive support, in catalysis for instance. The nanoparticles may have also to be surface functionalized by various species, and/or dispersed in aqueous or non aqueous media. We will show that the aqueous chemistry of metal cations is a very versatile and attractive way for the design of oxide nanomaterials, allowing the control of size, shape, and crystalline structure for polymorphic materials. Aqueous surface chemistry, including adsorption of various species, may be used to modify the morphology of nanoparticles. In some cases, redox processes can be involved to control the morphology of nanoparticles. Technologically important nanomaterials such as titania, alumina, and iron oxides are studied.     

Multiwalled carbon nanotubes@octavinyl polyhedral oligomeric silsesquioxanes nanocomposite preparation via cross-linking reaction in acidic media

Multiwalled carbon nanotubes have unique properties allowing their use in a wide range of applications—from microelectronics to biomedical and polymer fields. Nevertheless, a crucial aspect for their use resides in the ease of handling them during the process. Here, we report a facile route to prepare multiwalled carbon nanotubes@octavinyl polyhedral oligomeric silsesquioxanes (MWCNT@POSS) nanocomposite. The method involves the formation of a covalent bond between carboxylated MWCNTs and OV-POSS using acid-catalyzed electrophilic addition reaction. The resulting nanocomposite have been characterized by Fourier transform infrared spectroscopy (FTIR), powder X-Ray diffraction (PXRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and thermogravimetric analysis (TGA). The results confirmed that the formation of MWCNT@POSS nanocomposite did not deteriorate MWCNT structure or morphology. Here, we used a 1:1 ratio of carboxylated MWCNTs and OV-POSS and the POSS content in the nanocomposite was 39.5 wt%.     

Anionic, in situ generation of formaldehyde: a very useful and versatile tool in synthesis

A very simple, safe and powerful method for the in situ generation of formaldehyde at low temperature in anhydrous conditions is described. This new tool avoids the use of gaseous formaldehyde and is suitable for basic carbon nucleophiles which cannot be generated in aqueous reaction media. Various substrates, including organolithium reagents and enolates, underwent smooth hydroxymethylation showing the versatility of this process. A Wittig reaction was also carried out in high yield. [reaction: see text]     

Functionalization of silicon surfaces with Si-C linked beta-cyclodextrin monolayers

Vinyl-terminated heptapodyl beta-cyclodextrins react with hydrogenated silicon surfaces to generate covalently-bound molecular recognition devices.