Laboratoire P.A.S.T.E.U.R

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Taming Nickel-Catalyzed Suzuki-Miyaura Coupling: A Mechanistic Focus on Boron-to-Nickel Transmetalation

ACS Catal. 2018, 8, 4812−4823

 

The mechanism of boron-to-nickel transmetalation, the key step of the nickel-catalyzed Suzuki-Miyaura (SM) coupling, was examined both experimentally and theoretically. Dinuclear μ -hydroxo-bridged complexes formed by reaction of trans[ArNi(PR3)2X] with hydroxide are not directly involved in transmetalation, but they rather act as a resting state for the catalyst. The base/boronic acid ratio is the crucial parameter, as it modulates the extent of formation of these dinuclear species and thus tunes the catalytic activity. These findings explain some limitations encountered in practical applications of nickel-catalyzed S-M couplings and suggest how to tailor the experimental conditions in order to overcome these difficulties.

Fluorogenic Probing of Membrane Protein Trafficking

Bioconjugate Chem. 2018

 

Methods to differentially label cell-surface and intracellular membrane proteins are indispensable for understanding their function and the regulation of their trafficking. We present an effi cient strategy for the rapid and selective fluorescent labeling of membrane proteins based on the chemical-genetic fl uorescent marker FAST (fluorescence activating and absorption-shifting tag). Cell-surface FASTtagged proteins could be selectively and rapidly labeled using fluorogenic membrane-impermeant 4-hydroxybenzylidene rhodanine (HBR) analogs. This approach allows the study of protein trafficking at the plasma membrane with various fluorometric techniques, and opens exciting prospects for the high-throughput screening of small molecules able to restore disease-related trafficking defects.

A novel diarylethene-based photoswitchable chelator for reversible release and capture of Ca2+ in aqueous media

Nadia Dozova,Guillaume Pousse, Bogdan Barnych, Jean-Maurice Mallet, Janine Cossy, Bernard Valeur, Pascal Plaza

 

DOI:10.1016/j.jphotochem.2018.04.029

 

A photochromic calcium chelator is reported to reversibly reduce its affinity for calcium upon photoswitching in aqueous media.

 

 

Fast and complete electrochemical conversion of solutes contained in microvolume water droplets

Electrochemistry Communications 86 (2018) 145–148

 

An elegant hanging-droplet or meniscus-based setup is proposed to carry out quantitative electrolyses from either an organic (hydroquinone) or an inorganic (permanganate) substrate. These examples validate the concept of using such easily accessible, fast (1–3 min) and low-cost operating conditions not only for preparative applications (electrosynthesis), but also for pedagogical purposes in minute samples.

Electrochemical switching fluorescence emission in rhodamine derivatives

Electrochimica Acta 260 (2018) 589-597

 

Three rhodamine derivatives exhibiting electrofluorochromic properties were investigated by cyclic voltammetry and UVeVis/fluorescence spectroelectrochemistry. Rhodamine 101 (Rh101, compound 1) was used as a reference model. In compound 2, the carboxylate anion of Rh101 was replaced by an alkyne moiety to allow further functionalization. The compound 3 was prepared from 2 by conversion of the alkyne to a triazole group bearing an alkyl chain with an alcohol function. These three rhodamine derivatives exhibited similar electrochemical behaviors. Their mono-electronic reductions produced the corresponding radical species which were stable on the time-scale of cyclic voltammetry. Additional reduction of electrogenerated radicals produced unstable anions which underwent subsequent chemical reaction, most likely protonation. Based on cyclic voltammetry investigations, absorption and fluorescence spectroelectrochemistry were then performed on compounds 1, 2, 3 and their parent reduced radicals 1a, 2a, 3a. UVeVis spectroelectrochemistry, combined with TD-DFT calculation, confirmed the formation of radicals upon mono-electronic reduction of starting rhodamines. Fluorescence spectroelectrochemistry showed that, contrary to their parent molecules, electrogenerated radicals were non-fluorescent. Electrochemical fluorescence extinction was successfully achieved with all studied compounds. Moreover, compound 1 underwent on/off switching between fluorescent and nonfluorescent states repeatedly. Also, recovery of fluorescence in compound 3 was observed, which open interesting opportunities for the development of versatile rhodamine-based probes.