Evelyne Chelain
Centre national de la recherche scientifique
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Featured researches published by Evelyne Chelain.
Journal of Organometallic Chemistry | 2001
Henri Rudler; Virginie Comte; Eva Garrier; Moncef Bellassoued; Evelyne Chelain; Jacqueline Vaissermann
Abstract Potassium enolates derived from saturated and unsaturated bis(trimethylsilyl) ketene acetals react with tricarbonylchromium complexes of anisole and diphenylether to give, in addition to α-arylcarboxylic acids, the mono adducts, lactones, arising from a double exo nucleophilic addition. The latter were not observed in the case of benzenetricarbonylchromium. The intermediate dienol ethers could be isolated and fully characterized by X-ray crystallography. The influence of the nature of the substituents on the ketene acetals, of the nature of the oxidant, and of the nature of the ester enolates on the course of the reaction has been established and will be discussed.
Organic Letters | 2012
Julien Simon; Evelyne Chelain; Thierry Brigaud
The organolithium species addition to 2-hydroxymethyl fluorinated oxazolidines (Fox) provides a highly diastereoselective and straightforward route for the synthesis of enantiopure trifluoromethyl β-amino alcohols quaternarized at the β-position.
Biopolymers | 2015
Alexandra Botz; Vincent Gasparik; Emmanuelle Devillers; Anais R. F. Hoffmann; Lucie Caillon; Evelyne Chelain; Olivier Lequin; Thierry Brigaud; Lucie Khemtémourian
The extracellular deposition of insoluble amyloid fibrils resulting from the aggregation of the amyloid‐β (Aβ) is a pathological feature of neuronal loss in Alzheimers disease (AD). Numerous small molecules have been reported to interfere with the process of Aβ aggregation. Compounds containing aromatic structures, hydrophobic amino acids and/or the α‐aminoisobutyric acid (Aib) as β‐sheet breaker elements have been reported to be effective inhibitors of Aβ aggregation. We synthesized two peptides, one containing the Aib amino acid and the other including its trifluoromethylated analog (R)‐α‐Trifluoromethylalanine ((R)‐Tfm‐Alanine) and we evaluated the impact of these peptides on Aβ amyloid formation. The compounds were tested by standard methods such as thioflavin‐T fluorescence spectroscopy and transmission electron microscopy but also by circular dichroism, liquid state nuclear magnetic resonance (NMR) and NMR saturation transfer difference (STD) experiments to further characterize the effect of the two molecules on Aβ structure and on the kinetics of depletion of monomeric, soluble Aβ. Our results demonstrate that the peptide containing Aib reduces the quantity of aggregates containing β‐sheet structure but slightly inhibits Aβ fibril formation, while the molecule including the trifluoromethyl (Tfm) group slows down the kinetics of Aβ fibril formation, delays the random coil to β‐sheet structure transition and induces a change in the oligomerization pathway. These results suggest that the hydrophobic Tfm group has a better affinity with Aβ than the methyl groups of the Aib and that this Tfm group is effective and important in preventing the Aβ aggregation.
Amino Acids | 2016
Emmanuelle Devillers; Julien Pytkowicz; Evelyne Chelain; Thierry Brigaud
Considering the increasing importance of fluorinated peptides, the development of efficient and reliable synthetic methods for the incorporation of unnatural fluorinated amino acids into peptides is a current matter of interest. In this study, we report the convenient Boc/benzyl and Cbz/tert-butyl protection of both enantiomers of the quaternarized amino acid α-trifluoromethylalanine [(R)- and (S)-α-Tfm-Ala]. Because of the deactivation of the nitrogen atom of this synthetic amino acid by the strong electron withdrawing trifluoromethyl group, the peptide coupling on this position is a challenge. In order to provide a robust synthetic methodology for the incorporation of enantiopure (R)- and (S)-α-trifluoromethylalanines into peptides, we report herein the preparation of dipeptides ready to use for solid phase peptide synthesis. The difficult peptide coupling on the nitrogen atom of the α-trifluoromethylalanines was performed in solution phase by means of highly electrophilic amino acid chlorides or mixed anhydrides. The synthetic effectiveness of this fluorinated dipeptide building block strategy is illustrated by the solid phase peptide synthesis (SPPS) of the Ac-Ala-Phe-(R)-α-Tfm-Ala-Ala-NH2 tetrapeptide.
Chemical Communications | 1999
Moncef Bellassoued; Evelyne Chelain; Jérôme Collot; Henri Rudler; Jacqueline Vaissermann
Bis(trimethylsily)ketene acetals of the general structure 2 (R1 = H, Me, R2 = Me, Et, Pri, CMe=CH2) react at –78 °C in the presence of ButOK with a series of arenechromium tricarbonyl complexes 3 to give as expected, after oxidation with I2 followed by silica gel chromatography, arylcarboxylic acids 7. In the case of anisolechromium tricarbonyl 8, besides the m-methoxyarylcarboxylic acids, tetrahydrobenzofuran-2,5-diones 11, are formed as the result of a double nucleophilic addition.
ChemBioChem | 2018
Charlène Gadais; Emmanuelle Devillers; Vincent Gasparik; Evelyne Chelain; Julien Pytkowicz; Thierry Brigaud
In order to achieve accurate determination of the local hydrophobicity increases in peptide sequences produced by incorporation of trifluoromethylated amino acids (TfmAAs), the chromatographic hydrophobicity indexes (ϕ0) of three series of tripeptides containing three unnatural trifluoromethylated amino acids have been measured and compared with those of their non‐fluorinated analogues. The hydrophobic contribution of each fluorinated amino acid was quantified by varying the position and the protection of (R)‐ and (S)‐α‐trifluoromethylalanine (TfmAla), (R)‐trifluoromethylcysteine (TfmCys), and (S)‐trifluoromethionine (TFM) in a short peptide sequence. As a general trend, strong increases in hydrophobicity were precisely measured, even exceeding the high hydrophobic contribution of the natural amino acid isoleucine. This study validates the incorporation of trifluoromethylated amino acids into peptide sequences as a rational strategy for the fine‐tuning of hydrophobic peptide–protein interactions.
Journal of the American Chemical Society | 1992
Evelyne Chelain; Régis Goumont; Louis Hamon; A. Parlier; Michele Rudler; Henri Rudler; Jean Claude Daran; Jacqueline Vaissermann
Journal of the American Chemical Society | 1993
Evelyne Chelain; Andrée Parlier; Max Audouin; Henri Rudler; Jean Claude Daran; Jacqueline Vaissermann
Tetrahedron-asymmetry | 2011
Julien Simon; Thi Thuan Nguyen; Evelyne Chelain; Nathalie Lensen; Julien Pytkowicz; Grégory Chaume; Thierry Brigaud
European Journal of Organic Chemistry | 2007
Sylvie Dhulut; Arnaud Bourin; Marie-Isabelle Lannou; Etienne Fleury; Nathalie Lensen; Evelyne Chelain; Ange Pancrazi; Janick Ardisson; Jacques Fahy