Synthèse et études structurales de nouveaux [alpha/aza]-oligomères et cyclooligomères, vers de nouveaux foldamères

Abstract : This work describes the synthesis and structural analysis of mixed oligomers and their cyclic analogues containing an alternation of [alpha]-acid residues and [alpha]-azaamino acids moieties. The first chapter deals with the “in solution” synthesis of 1:1-[[alpha]/aza]-oligomers and 2:1 [[alpha]/aza] oligomers respectively, obtained by oligomerization of the properly deprotected azadipeptide Boc-Ala-azaPhe-OMe azadipeptide and Boc-Phe-Ala-OMe-azaPhe tripeptide. For the first family series with L aminoacids, yields dimerization and trimerization are moderate due to the low nucleophilicity of the amine azadipeptidic partner. Concerning the 2:1-[[alpha]/aza]-oligomers of variable sizes, they were isolated with very good yields whatever the nature L and / or D of the [alpha]-aminoacid residues of the azatripeptide. This chapter also presents the conformational study of these oligomers by NMR and IR spectroscopy, molecular modeling and in some cases by X-ray diffraction. Analysis of the 1:1 [[alpha]/aza] oligomers reveals mainly an self-assembly in solution with alternation of [beta]- and [gamma]-turns stabilized by intramolecular hydrogen bonds. Examination of the 2:1 [[alpha]/aza] oligomers in homochiral series (L) evidenced a main conformation with repetitive [beta] turns. Regarding the heterochiral series (DLDL….), it is an alternation of [beta]- and [gamma]-turns which is observed. The second chapter is devoted to the solution synthesis in solution and conformational study of cyclic analogues oligomers presented in the first chapter. 2: 1-[[alpha]/aza]-cyclooligomers are mostly discussed because their synthesis by intramolecular peptide coupling is more effective than the 1:1 [[alpha]/aza]-cyclooligomers. The formation of nanotubes due to the stacking of the homochiral (L) 2:1-[[alpha]/aza]-cyclohexamers has been shown in the solid state and suggested in solution. Furthermore, in heterochiral series, the gelling properties of some organic solvents suggest a self-assembly in solution
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Zhou Zhou. Synthèse et études structurales de nouveaux [alpha/aza]-oligomères et cyclooligomères, vers de nouveaux foldamères. Autre. Université de Lorraine, 2014. Français. ⟨NNT : 2014LORR0300⟩. ⟨tel-01751410⟩

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