3 research outputs found
Preparation and applications of new xylosides containing functionalised aglycons for organic synthesis and asymetric homogeneous catalysis
Le D-(+)-xylose est un pentose abondamment présent dans la biomasse (environ 25 à 30% de la matière sèche). Il représente donc un synthon issu des agro-ressources régionales très intéressant à étudier et à valoriser pour des applications dans différents domaines. Le D-xylose peut facilement être transformé en xyloside par une réaction de glycosylation chimique avec divers alcools fonctionnalisés. Ces xylosides visés présentant des parties aglycones avec des fonctions chimiques modulables serviront de matières premières pour les travaux envisagés au cours de la thèse. Dans un premier temps, la chiralité intrinsèque du xylose sera exploitée dans le développement de nouvelles copules chirales pour des transformations stéréosélectives en chimie organique. Les objectifs de cette partie concerneront la synthèse de nouveaux allènes chiraux à partir de propargyl xylosides et leurs transformations vers de nouvelles molécules plus élaborées. Par la suite, la synthèse de phospholes chiraux à base de xylose sera envisagée pour des applications en catalyse homogène énantiosélective. Une troisième voie de valorisation consistera à préparer de nouveaux ligands à amphiphilie modulable pour la complexation de cations d'or (I) et d'or (III) pour des applications biologiques.D-(+)xylose is a pentose abundantly present in biomass (around 25 to 30% of dry material). It presents a ver
Diastereoselective synthesis of axially chiral xylose-derived 1,3-disubstituted alkoxyallenes: scope, structure and mechanism
International audienceThe deprotonation of differently substituted propargyl xylosides with s-BuLi/TMEDA followed by protonation with t-butanol at-115 °C provided a range of new axially chiral 1,3-disubstituted alkoxyallenes in a diastereoselective way. Numerous reaction parameters such as solvent, temperature or protonating agent were examined as well as protecting groups on the xyloside moiety and the influence of the substituents on the alkyne part. The configuration of the main dia-stereoisomer of 3-methyl-1-xyloside-allene was determined for the first time by single crystal X-ray diffraction analysis and nOe NMR experiments. Furthermore, DFT calculations on the propargyl/allenyl lithium intermediates formed in the course of the deprotonation reaction provided new structural insights of these complexes. The subsequent protonation process with alcohols was investigated by theoretical surface exploration, revealing the importance of the approach of the alcohol towards the lithium compounds on the reaction outcome
Diastereoselective Synthesis of Axially Chiral Xylose-Derived 1,3-Disubstituted Alkoxyallenes: Scope, Structure, and Mechanism
International audienceThe deprotonation of differently substituted propargyl xylosides with s-BuLi/TMEDA followed by protonation with t-butanol at-115 °C provided a range of new axially chiral 1,3-disubstituted alkoxyallenes in a diastereoselective way. Numerous reaction parameters such as solvent, temperature or protonating agent were examined as well as protecting groups on the xyloside moiety and the influence of the substituents on the alkyne part. The configuration of the main dia-stereoisomer of 3-methyl-1-xyloside-allene was determined for the first time by single crystal X-ray diffraction analysis and nOe NMR experiments. Furthermore, DFT calculations on the propargyl/allenyl lithium intermediates formed in the course of the deprotonation reaction provided new structural insights of these complexes. The subsequent protonation process with alcohols was investigated by theoretical surface exploration, revealing the importance of the approach of the alcohol towards the lithium compounds on the reaction outcome