Chloration et S-oxydation du benzo[b]thiophène par l'hypochlorite de tertiobutyle. Mécanisme de la réaction

In the reaction with benzothiophene, t-butyl hypochlorite acts simultaneously as a smooth oxidizing agent and as a chlorinating agent since it is a source of both hypochlorous acid and chlorine. The mixture of all the products obtained imply that the reaction intermediate is the unstable benzothiophene I-oxide which was shown to be present by the stop flow technique. The chlorine formed traps the highly reactive benzothiophene 1-oxide in situ to give the observed products.     

Etude par RMN et rayons X de sesquicarbure d'uranium

We have measured the position and linewidth of the ¹³C NMR signal in U₂ C₃ between 4 and 300 K. This study confirms the existence of an electronic transition around 50 K which brings possibly a non magnetic fundamental state. This transition involves no crystallographic distorsion and no lattice parameter anomaly.     

In-capillary non-covalent labeling of insulin and one gastrointestinal peptide for their analyses by capillary electrophoresis with laser-induced fluorescence detection

The potential of the commercially available dye sypro orange for in-capillary derivatization was evaluated for the detection of insulin and one gastrointestinal peptide (Arg-Arg-gastrin) by capillary electrophoresis with laser induced fluorescence (CE-LIF). The fluorescent emission intensity (lambda(ex) = 488 nm, lambda(em) = 610 nm) of this probe is very low in aqueous medium, and increases strongly in less polar solvent, e.g. methanol. The hydrophobic character of the two analyzed peptides is too low to induce sufficient interaction with the fluorescent probe for good sensitivity when the latter is alone in the background electrolyte. Thus, the potential of several neutral, zwitterionic, cationic and anionic surfactants to favor probe/peptide interactions has been evaluated. It was demonstrated that a borate buffer (pH 8.5) containing tetradecyltrimethylammonium bromide (TTAB) in sub-micellar conditions can be considered as the most suitable buffer for insulin CE-LIF analysis. In addition, the method showed a good linearity between insulin concentration and the peak area of the labeled insulin, allowing quantitative measurements. The sensitivity achieved so far is comparable with that achieved with UV absorption detection, but even at this level it is interesting for microchip analysis, in which fluorescence detection is much more commonly available than UV absorption detection.     

Discovery of powerful uranyl ligands from efficient synthesis and screening

New tripodal gem-(bis-phosphonates) uranophiles were discovered by a screening method that allowed for the selection of ligands with strong uranyl-binding properties in a convenient microtiter-plate format. The method is based on competitive uranium binding by using Sulfochlorophenol S as chromogenic chelate. This dye compound was found to present high uranyl complexation properties and allowed to highlight ligands presenting association constants for UO(2+)(2) up to 10(18) at pH 7.4 and 10(20) at pH 9. A collection of 40 known ligands including polycarboxylate, hydroxamate, catecholate, hydroxypyridonate and hydroxyquinoline derivatives was tested. Also screened was a combinatorial library prepared from seven amine scaffolds and eight acrylates bearing diverse chelating moieties. Among these 96 tested candidates, a tripod derivative bearing gem-bis-phosphonates moieties was found to present the highest complexation properties over a wide range of pH and was further studied.