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Réductions énantiosélectives de cétones (approches synthétiques du stémoamide et de ses analogues)

PARIS-BIUSJ-Thèses (751052125) / SudocPARIS-BIUSJ-Physique recherche (751052113) / SudocSudocFranceF

Kinetic study of azobenzene E/Z isomerization using liquid chromatography and ion mobility-mass spectrometry

International audienceAzobenzene molecular switches can interconvert both photochemically and thermally. Due to the great interest focused toraised by azobenzene’s photochromic properties, their fast identification has become a challenge. Usually identified using UV-VIS spectrophotometry, we propose different coupling to MS such as ion mobility spectrometry (IMS) and liquid chromatography (LC) to study the Z to E isomerisation. This process, known as thermal back relaxation, spontaneously occurs in the dark, where the metastable E isomer relaxes towards the thermodynamically more stable Z form. In the specific case of cyclic azobenzene, three isomers were isolated: two stable diastereomers with Z stereochemistry and an unstable E conformer .Analyses of isomers by tandem mass spectrometry were carried out on azobenzene sample using different metallic salts and generating ternary complexes without allowing differentiation of isomers. An upstream separation dimension was then necessary to characterize each isomer. For these compounds, IMS-MS and LC-(UV)-MS were evaluated in parallel to study the kinetics of thermal Z to E isomerisation. On one hand, baseline separation of Z isomers was achieved in IMS-MS from [M+Ag]+ ions, while the E conformer was differentiated from the dimers [2M+Ag]+. On the other hand, LC separation of the three isomers was achieved in less than 10 minutes. These methodologies can be applied to different systems in order to determine the thermal back relaxation kinetic of unstable isomers. However, IMS-MS method will be preferred for fast systems as it allowed isomers separation in the millisecond time scale

Kinetic study of azobenzene E/Z isomerization using ion mobility-mass spectrometry

National audienc

Kinetic study of azobenzene E/Z isomerization using ion mobility-mass spectrometry

International audienceIntroductionAzobenzene molecular switches can interconvert both photochemically and thermally. Due to their important development, their fast identification has become a challenge. Usually identified using UV-VIS spectrophotometry, we propose different coupling to MS such as ion mobility spectrometry and liquid chromatography to study the thermal Z to E back relaxation kinetic of isomers.MethodsDifferent synthetized isomerically pure azobenzenes were analysed in MS/MS using different cation adducts. LC experiments were performed using a 1260 series Infinity system packed with a Kinetex XB C-18 column coupled to an ion trap mass analyser (AmaZon speed ETD). Ion mobility-mass spectrometry experiments were carried out on a hybrid instrument (Synapt G2-Si HDMS) equipped with an ESI source. ResultsAnalyses of isomers by tandem mass spectrometry were carried out on different azobenzene pairs and an azobenzene sample consisting of three isomers. Differentiation of isomers was achieved for isomer couples using MS/MS. An upstream separation dimension was necessary to characterise the sample with three isomers. For these compounds, IMS-MS and LC-(UV)-MS were evaluated in parallel to study the kinetic of thermal Z to E isomerisation. Baseline separation of two isomers was achieved in IMS-MS from [M+Ag]+, while the third isomer was differentiated from [2M+Ag]+. In addition, LC separation of the three isomers was achieved in less than 10 minutes. These methodologies can be applied to different systems in order to determine their thermal back relaxation kinetic. IMS-MS and MS/MS methods will be preferred for fast systems as they allowed differentiation in the millisecond scale.Novel AspectFor the first time, the thermal back relaxation kinetic of azobenzene isomers is studied using hyphenated techniques (IMS and LC) to MS and MS/MS

Design of Light-Sensitive Triggers for Endothelial NO-Synthase Activation

A specific light trigger for activating endothelial Nitric Oxide-Synthase (eNOS) in real time would be of unique value to decipher cellular events associated with eNOS activation or to generate on demand cytotoxic levels of NO at specific sites for cancer research. We previously developed novel tools called nanotriggers (NT), which recognized constitutive NO-synthase, eNOS or neuronal NOS (nNOS), mainly via their 2’ phosphate group which is also present in NADPH in its binding site. Laser excitation of NT1 bound to eNOS triggered recombinant NOS activity and released NO. We recently generated new NTs carrying a 2’ or 3’ carboxylate group or two 2’ and 3’ carboxylate moieties replacing the 2’ phosphate group of NADPH. Among these new NT, only the 3’ carboxylate derivative released NO from endothelial cells upon laser activation. Here, Molecular Dynamics (MD) simulations showed that the 3’ carboxylate NT formed a folded structure with a hydrophobic hub, inducing a good stacking on FAD that likely drove efficient activation of nNOS. This NT also carried an additional small charged group which increased binding to e/nNOS; fluorescence measurements determined a 20-fold improved affinity upon binding to nNOS as compared to NT1 affinity. To gain in specificity for eNOS, we augmented a previous NT with a “hook” targeting variable residues in the NADPH site of eNOS. We discuss the potential of exploiting the chemical diversity within the NADPH site of eNOS for reversal of endothelial dysfunction in cells and for controlled generation of cytotoxic NO-derived species in cancer tissues

Triphenylphosphine Photorelease and Induction of Catalytic Activity from Ruthenium-Arene Complexes Bearing a Photoswitchable <i>o</i>‑Tosylamide Azobenzene Ligand

The reactivity of cationic arene ruthenium complexes bearing a photoswitchable <i>o</i>-tosylamide azobenzene ligand toward various phosphorus nucleophiles was investigated. The resulting phosphine-ruthenium complexes containing an azobenzene ligand were isolated as the <i>Z</i> isomer. Under appropriate reaction conditions, quantitative triphenylphosphine photorelease from the complex was achieved through <i>Z</i> → <i>E</i> isomerization of the ligand. This process was applied to the photoinitiation of the catalytic aza-Morita–Baylis–Hillman reaction

Triphenylphosphine Photorelease and Induction of Catalytic Activity from Ruthenium-Arene Complexes Bearing a Photoswitchable <i>o</i>‑Tosylamide Azobenzene Ligand

The reactivity of cationic arene ruthenium complexes bearing a photoswitchable <i>o</i>-tosylamide azobenzene ligand toward various phosphorus nucleophiles was investigated. The resulting phosphine-ruthenium complexes containing an azobenzene ligand were isolated as the <i>Z</i> isomer. Under appropriate reaction conditions, quantitative triphenylphosphine photorelease from the complex was achieved through <i>Z</i> → <i>E</i> isomerization of the ligand. This process was applied to the photoinitiation of the catalytic aza-Morita–Baylis–Hillman reaction

Optimizing the formation of biocompatible gold nanorods for cancer research: Functionalization, stabilization and purification

International audienc

Photoswitchable Arene Ruthenium Complexes Containing o‑Sulfonamide Azobenzene Ligands

A series of arene ruthenium complexes containing <i>o</i>-sulfonamide azobenzene ligands were synthesized and found to exhibit uncommon coordination pattern with an exocyclic NN bond. Upon irradiation, these complexes cleanly undergo <i>E</i> → <i>Z</i> photoisomerization followed by thermal <i>Z</i> → <i>E</i> isomerization (upon resting in the dark) whose rate is dependent on the solvent, the nature of the arene group, the sulfonamide moiety, and azobenzene substitution, as revealed by structure–property studies