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Productions scientifiques

Gaudel-Siri, Anouk.

ACL - Articles dans des revues à comité de lecture

15 références.

  • Baron, M.; Rakotorinina, M. - D.; El Assil, M. I.; Guillaneuf, Y.; Gigmes, D.; Siri, D.; Gaudel-Siri, A.; Flat, J. - J.; Quinebeche, S.; Cassagnau, P.; Beyou, E. Materials Today Communications 2019, 19, 271-276.
    Résumé : For the first time, the melt radical grafting of diethylmaleate (DEM) and maleic anhydride (MA) onto oligoamide-11 (OA11) and polyamide-11 (PA11) was performed in presence of new acyloxyimide derivatives in the temperature range 190 degrees C-250 degrees C in an autoclave and a mini-extruder, respectively. The DEM grafting degree was studied as a function of reaction temperature, the DEM concentration, the acyloxyimide concentration and its chemical structure. The degree of grafting of DEM was determined by H-1 NMR and we obtained a DES (diethylsuccinimate) functionalization degree (FD) as high as 9 mol% onto OA11 when using tBu-NAPI as Habstractor at 230 degrees C. However, the transposition of this grafting reaction at a pilot scale did not permit to obtain such a high DES FD while the morphological study of PA11/EVOH blends with the grafted copolymer did not significantly improve the adhesion between the two phases.

  • Gaudel-Siri, A.; Marchal, C.; Ledentu, V.; Gigmes, D.; Siri, D.; Charles, L. European Journal of Mass Spectrometry 2019, 25 (2), 229-238.
    Résumé : The dissociation behavior of two stable nitroxides, namely 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO center dot) and N-tert-butyl-1-diethylphosphono-2,2-dimethylpropyl nitroxide (SG1(center dot)), subjected as protonated molecules to collisional activation was investigated using a combination of different mass spectrometry experiments and theoretical calculations. Elemental composition of reaction products was derived from accurate mass data measured in high resolution tandem mass spectrometry experiments, primary fragments were distinguished from secondary ions based on both breakdown curves and MS3 data, and H/D exchange experiments were performed to support proposed structures. Postulated fragmentation pathways were then studied in terms of energetic, using the standard B3LYP/6-31G(d) method. While protonation of TEMPO center dot mainly occurred on the oxygen atom of the nitroxyl function, a series of protomers were found for SG1(center dot) with the adducted proton preferentially located onto the P=O group of this phosphorylated species. For both protonated nitroxides, major product ions measured in tandem mass spectrometry arose from reactions occurring at low energy costs via elimination of radical species. Formation of secondary fragments that were detected with low abundance when raising the activation level of both precursor ions could be rationalized with pathways proceeding via high energy transition states.

  • Rakotonirina, M. D.; Baron, M.; Siri, D.; Gaudel-Siri, A.; Quinebeche, S.; Flat, J. - J.; Gigmes, D.; Cassagnau, P.; Beyou, E.; Guillaneuf, Y. Polymer Chemistry 2019, 10 (31), 4336-4345.
    Résumé : Acyloxyimides as a new H-abstracting agent have been developed for the radical grafting of maleic anhydride (MA) onto polyethylene in the melt state. Their model decomposition in DMSO-d6 as well as in tetradecane that mimics polyolefins was performed. These studies confirmed first the complete decomposition of N-acetoxyphthalimide (NAPI) in 1 hour at 180 degrees C by a N-O bond dissociation mechanism and also the patching of the produced macroradicals by the phthalimide group. The reaction was then performed in a mini-extruder at 190-250 degrees C and the hydrogen abstraction ability of N-acyloxyphthalimide (NAP)-, N-acyloxynaphthalimide (NANP)- and N-acyloxysuccinimide (NAS)-based derivatives was demonstrated. Optimal experimental conditions were determined by varying the initial MA content and the degree of grafting of MA was quantified by infrared spectroscopy. The MA grafting degree was as high as 2.98 wt% when using tBu-NAP as the H-abstracting agent at 230 degrees C with only a slight modification of the PE chain structures as proved by rheological experiments while the use of a peroxide (L101) led to a lower grafting degree (1.9 wt%) and a cross-linking of the polymer chains, confirmed by the three-five fold higher complex viscosity.

  • Lescic, S.; Karoui, H.; Hardy, M.; Charles, L.; Tordo, P.; Ouari, O.; Gaudel-Siri, A.; Siri, D. Journal of Physical Organic Chemistry 2017, 30 (10), e3677.
    Résumé : Spin trapping coupled with electron paramagnetic resonance spectroscopy is the most direct method for detection of very low concentrations of free radicals, and it has been intensively used to detect superoxide or alkylperoxyl radicals in biological systems, using cyclic nitrones as spin traps. The half-life time of the ensuing spin adducts depends dramatically on the spin trap structure; however, their mechanism of decay has never been definitely established. We investigated at the MRMP2/CASSCF (MultiReference second-order Moller-Plesset perturbation theory/Complete Active Set Self Consistent Field) level of theory the mechanism of decay of methylperoxyl and tert-butylperoxyl spin adducts formed with various cyclic nitrones. We showed that no transition state can be located for the O-O homolytic cleavage, which yields an intermediate biradical with the following sequence O-center dot-N-C-O-center dot. Then, homolytic cleavage of the N-C bond yields a nitrosoaldehyde, through an early transition state with a very low activation energy. For each nitrone used as spin trap, electrospray ionization mass spectrometry analysis of the spin trapping mixture allowed to detect the presence of the expected nitrosoaldehyde. We generated tert-butylperoxyl spin adducts in toluene, and we found a good correlation between their half-life time and the bond dissociation energy of their peroxidic O-O bond. The theoretical method was then extended to hydroperoxyl spin adducts in water and provided promising results.
    Mots-clés : 2nd-order perturbation-theory, alkylperoxyl spin adducts, biradical, centered radicals, cyclic nitrones, depmpo, dft, dmpo, epr, half-life time, mrmp2/casscf, radical-anion adduct, spin trapping, superoxide, trapping properties.

  • Poulhes, F.; Rizzato, E.; Bernasconi, P.; Rosas, R.; Viel, S.; Jicsinszky, L.; Rockenbauer, A.; Bardelang, D.; Siri, D.; Gaudel-Siri, A.; Karoui, H.; Hardy, M.; Ouari, O. Organic & Biomolecular Chemistry 2017, 15 (30), 6358–6366.
    Résumé : Three new DEPMPO-based spin traps have been designed and synthesized for improved superoxide detection, each carrying a cyclodextrin (CD) moiety but with a different alkyl chain on the phosphorus atom or with a long spacer arm. EPR spectroscopy allowed us to estimate the half-life of the superoxide spin adducts which is close to the value previously reported for CD-DEPMPO (t(1/2) approximate to 50-55 min under the conditions investigated). The spectra are typical of superoxide adducts (almost no features of the HO center dot adduct that usually forms with time for other nitrone spin traps such as DMPO) and we show that at 250 mu M, the new spin trap enables the reliable detection of superoxide by 1 scan at the position opposite to the corresponding spin trap without the CD moiety. The resistance of the spin adducts to a reduction process has been evaluated, and the superoxide spin adducts are sensitive to ascorbate and glutathione (GSH), but not to glutathione peroxidase/GSH, reflecting the exposed nature of the nitroxide moiety to the bulk solvent. To understand these results, 2D-ROESY NMR studies and molecular dynamics pointed to a shallow or surface self-inclusion of the nitrone spin traps and of nitroxide spin adducts presumably due to the high flexibility of the permethyl-beta-CD rim.
    Mots-clés : conjugate, cyclic nitrone, depmpo, epr, in-vivo, inclusion, metabolic stability, radical adducts, resonance, trapping properties.

  • Thetiot-Laurent, S.; Gosset, G.; Clement, J. - L.; Cassien, M.; Mercier, A.; Siri, D.; Gaudel-Siri, A.; Rockenbauer, A.; Culcasi, M.; Pietri, S. Chembiochem 2017, 18 (3), 300–315.
    Résumé : There is increasing interest in measuring pH in biological samples by using nitroxides with pH-dependent electron paramagnetic resonance (EPR) spectra. Aiming to improve the spectral sensitivity (Delta a(x)) of these probes (i.e., the difference between the EPR hyperfine splitting (hfs) in their protonated and unprotonated forms), we characterized a series of novel linear alpha-carboxy, alpha'-diethoxyphosphoryl nitroxides constructed on an amino acid core and featuring an (alpha or alpha')-C-H bond. In buffer, the three main hfs (a(N), a(H), and a(P)) of their EPR spectra vary reversibly with pH and, from a(P) or a(H) titration curves, a two-to fourfold increase in sensitivity was achieved compared to reference imidazoline or imidazolidine nitroxides. The crystallized carboxylate 10b (pK(a) approximate to 3.6), which demonstrated low cytotoxicity and good resistance to bioreduction, was applied to probe stomach acidity in rats. The results pave the way to a novel generation of highly sensitive EPR pH markers.
    Mots-clés : EPR spectroscopy, intracellular ph, living cells, magnetic-resonance, molecular dynamics, n-oxide, nitroxide, oxidative stress, p-31 nmr, rat-liver, ring nitroxides, sensors, spin labels, stomach acidity, substituted nitroxides.

  • Quintard, A.; Cheshmedzhieva, D.; Duque, M. del M. S.; Gaudel-Siri, A.; Naubron, J. - V.; Genisson, Y.; Plaquevent, J. - C.; Bugaut, X.; Rodriguez, J.; Constantieux, T. Chemistry-a European Journal 2015, 21 (2), 778-790.
    Résumé : The organocatalytic enantioselective conjugate addition of secondary beta-ketoamides to alpha,beta-unsaturated carbonyl compounds is reported. Use of bifunctional Takemoto's thiourea catalyst allows enantiocontrol of the reaction leading either to simple Michael adducts or spirocyclic aminals in up to 99% ee. The origin of the enantioselectivity has been rationalised based on combined DFT calculations and kinetic analysis. This study provides a deeper understanding of the reaction mechanism, which involves a predominant role of the secondary amide proton, and clarifies the complex interactions occurring between substrates and the catalyst.

  • Bardelang, D.; Casano, G.; Poulhes, F.; Karoui, H.; Filippini, J.; Rockenbauer, A.; Rosas, R.; Monnier, V.; Siri, D.; Gaudel-Siri, A.; Ouari, O.; Tordo, P. Journal of the American Chemical Society 2014, 136 (50), 17570-17577.
    Résumé : The flexible tetranitroxide 4T has been prepared and was shown to exhibit a nine line EPR spectrum in water, characteristic of significant through space spin exchange (J(ij)) between four electron spins interacting with four nitrogen nuclei (J(ij) >= a(N)). Addition of CB[8] to 4T decreases dramatically all the J(ij) couplings, and the nine line spectrum is replaced by the characteristic three line spectrum of a mononitroxide. The supramolecular association between 4T and CB[8] involves a highly cooperative asymmetric complexation by two CB[8] (K-1 = 4027 M-1; K-2 = 202 800 M-1; alpha = 201) leading to a rigid complex with remote nitroxide moieties. The remarkable enhancement for the affinity of the second CB[8] corresponds to an allosteric interaction energy of approximate to 13 kJ mol(-1), which is comparable to that of the binding of oxygen by hemoglobin. These results are confirmed by competition and reduction experiments, DFT and molecular dynamics calculations, mass spectrometry, and liquid state NMR of the corresponding reduced complex bearing hydroxylamine moieties. This study shows that suitably designed molecules can generate allosteric complexation with CB[8]. The molecule must (i) carry several recognizable groups for CB[8] and (ii) be folded so that the first binding event reorganizes the molecule (unfold) for a better subsequent recognition. The presence of accessible protonable amines and H-bond donors to fit with the second point are also further stabilizing groups of CB[8] complexation. In these conditions, the spin exchange coupling between four radicals has been efficiently and finely tuned and the resulting allosteric complexation induced a dramatic stabilization enhancement of the included paramagnetic moieties in highly reducing conditions through the formation of the supramolecular 4T@CB[8](2) complex.

  • Gaudel-Siri, A.; Campolo, D.; Mondal, S.; Nechab, M.; Siri, D.; Bertrand, M. P. Journal of Organic Chemistry 2014, 79 (19), 9086-9093.
    Résumé : This article reports a theoretical study to explain how the intrinsic property of chirality is retained throughout the radical cascade rearrangement of an enantiopure chiral enyne-allene (bearing one stereogenic center) selected as a model for this family of reactions. Calculations at the MRPT2/6-31G(d)//CASSCF(10,10)/6-31G(d) level of theory were used to determine the entire reaction pathway which includes singlet state diradicals and closed-shell species. The cascade process involves three elementary steps, i.e., by chronological order: Myers-Saito cycloaromatization (M-S), intramolecular hydrogen atom transfer (HAT), and recombination of the resulting biradical. The enantiospecificity of the reaction results from a double transmission of the stereochemical information, from the original center to an axis and eventually from this axis to the final center. The first two steps lead to a transient diradical intermediate which retains the chirality via the conversion of the original static chirogenic element into a dynamic one, i.e., a center into an axis. The only available routes to the final closed-shell tetracyclic product imply rotations around two sigma bonds (sigma(C-C) and sigma(C-N), bonds beta and alpha respectively). The theoretical calculations confirmed that the formation of the enantiomerically pure product proceeds via the nonracemizing rotation around the sigma(C-C) pivot. They ruled out any rotation around the second sigma(C-N) pivot. The high level of configurational memory in this rearrangement relies on the steric impediment to the rotation around the C-N bond in the chiral native conformation of the diradical intermediate produced from tandem M-S/1,5-HAT.

  • Audran, G.; Bremond, P.; Marque, S. R. A.; Gaudel-Siri, A.; Siri, D.; Santelli, M. Tetrahedron Letters 2013, 54 (48), 6607-6610.
    Résumé : Epoxidation of vinylallenes (1,2,4-pentatrienes) can lead to cyclopent-2-enones. Various experimental results suggest that these reactions are concerted and that vinylallene oxides undergo a concerted and thermal ring-closing reaction to give cyclopentenones. In 1977, this view has been supported by the epoxidation of a non-racemic 4-methyl-2,3,5-hexatriene to give a non-racemic 2,5-dimethy1-2-cyclopenten-1-one. Indeed, for the cyclization of (3E)-4-methyl-2,3-epoxy-2,3,5-hexatriene or (4-E)-4-methyl-3,4epoxy-2,3,5-hexatriene into 2,5-dimethy1-2-cyclopenten-1-one, a transition structure for the concerted rearrangement was located, and IRC calculations showed it linked together. The activation barrier predicted at the B3LYP/6-311++G(3df,3pd)//B3LYP/6-31G(d) level of theory is 80.9 or 124.2 kJ mol(-1), respectively and the reaction is exothermic by 127.2 or 89.2 kJ mol(-1), respectively. (C) 2013 Elsevier Ltd. All rights reserved.

  • Campolo, D.; Gaudel-Siri, A.; Mondal, S.; Siri, D.; Besson, E.; Vanthuyne, N.; Nechab, M.; Bertrand, M. P. Journal of Organic Chemistry 2012, 77 (6), 2773-2783.
    Résumé : Memory of chirality (MOC) and deuterium-labeling studies were used to demonstrate that the cascade rearrangement of enediyne-connected amino esters la and 1b evolved through. exclusive 1,5- or 1,6-hydrogen atom transfer, subsequent to 1,3-proton shift and Saito-Myers cyclization, depending on the structure of the staffing material. These results were independently confirmed by DFT theoretical calculations performed on model monoradicals. These calculations clearly demonstrate that in the alanine series, 1,5-hydrogen shift is kinetically favored over 1,6-hydrogen shift because of its greater exergonicity. In the valine series, the bulk of the substituent at the nitrogen atom has a major influence on the fate of the reaction. N-Tosylation increases the barrier to 1,5-hydrogen shift to the benefit of 1,6-hydrogen shift. The ready availability of 1,6- hydrogen atom tansfer was explored as a potential route for the enantioselective synthesis of naphthoazepines.

  • Duque, M. del M. S.; Basle, O.; Isambert, N.; Gaudel-Siri, A.; Genisson, Y.; Plaquevent, J. - C.; Rodriguez, J.; Constantieux, T. Organic Letters 2011, 13 (13), 3296-3299.
    Résumé : The secondary amido group of a-substituted beta-ketoamides plays a crucial role in the control of the reactivity and spatial arrangement (selectivity) in the organocatalyzed Michael addition to unsaturated carbonyls. This results in an unprecedented activation mode of substrates through H-bonding interactions allowing the construction of enantiomerically enriched functionalized all-carbon quaternary centers and spiroaminals of high synthetic potential.

  • Hamadouche, M.; Gaudel-Siri, A.; Pons, J. - M.; El Abed, D. Journal of Molecular Structure-Theochem 2010, 956 (1-3), 33-37.
    Résumé : Triazolinic compounds are often unstable and lead to degradation products, mainly by ring opening. Among six 1,2,3-triazolines (T1-T6) synthesized by 1,3-dipolar cycloaddition, three triazolines (T1-T3) have been experimentally isolated. This work is a theoretical study at the MP2/6-311+G(d,p)//B3LYP/6-31+G(d,p) level of the relative stability of this series of triazolinic systems. Geometry and NBO analysis of the triazolinic rings show substituent effects on ring stability but are not completely satisfying. Then, whole reaction profiles (cycloaddition and ring opening) are calculated. While activation enthalpies and TS geometries of the first step are similar, activation enthalpies and TS geometries of the second step show some differences and partly explain relative stabilities. (C) 2010 Elsevier B.V. All rights reserved.

  • Lansalot, M.; Guillaneuf, Y.; Luneau, B.; Acerbis, S.; Dufils, P. - E.; Gaudel-Siri, A.; Gigmes, D.; Marque, S. R. A.; Tordo, P.; Bertin, D. Macromolecular Reaction Engineering 2010, 4 (6-7), of (M) over bar (n) = 210 000 g.mol(-1) with a living fraction of 60%. Finally, new SG1-based nitroxides were used to perform the polymerization at 75 degrees C. Since these nitroxides were too constrained, the decrease in k(c) caused a loss of control and livingness for high-(M) over bar (n) polymers.
    Résumé : The synthesis of high-molecular-weight living/controlled polystyrene by NMP was studied. The combination of Ac2O and alkoxyamines based on nitroxides TEMPO, TIPNO, and SG1 was tested at 130 degrees C. With TEMPO and TIPNO, dipole/dipole interactions led to a decrease in nitroxide concentration and an acceleration of the reaction. To minimize thermal auto-initiation and thus obtain high-(M) over bar (n) PS, the temperature was lowered. At 90 degrees C, the use of BlocBuilder yielded

  • Mathew, S. C.; By, Y.; Berthault, A.; Virolleaud, M. - A.; Carrega, L.; Chouraqui, G.; Commeiras, L.; Condo, J.; Attolini, M.; Gaudel-Siri, A.; Ruf, J.; Rodriguez, J.; Parrain, J. - L.; Guieu, R. Organic & Biomolecular Chemistry 2010, 8 (17), 3874-3881.
    Résumé : The synthesis of new C-6 1,2,3-triazole adenosine derivatives via microwave assisted 1,3-dipolar cycloaddition as key step is described. The binding on membranes of cells that over express A(1) adenosine receptors (A(1)AR) was also evaluated. Among them, four compounds increased cAMP production, in a dose-dependent manner acting as antagonists of the A(1)AR, while two compounds act as agonists.