Catalyse dans l'eau en présence de cyclodextrine native ou modifiée (Application au couplage croisé de type Suzuki)

Depuis quelques années, les acteurs du secteur de la chimie se sont donnés pour mission prioritaire de concevoir des produits et des procédés chimiques plus respectueux de l environnement afin de répondre aux préoccupations environnementales. Ainsi, les douze principes du concept de la chimie verte sont nés. L un de ces principes est de substituer, lors des synthèses, les solvants organiques, généralement toxiques, par des solvants plus éco-compatibles comme l eau et d un point de vue plus général, la catalyse joue un rôle majeur dans cette politique de chimie verte puisqu elle permet de réduire la consommation d énergie, de diminuer la quantité des réactifs utilisés ainsi que les procédés de séparation par augmentation de la sélectivité. Cependant, la faible solubilité dans l eau des substrats organiques ne permet pas l obtention de bons rendements. Afin de pallier ce problème, la catalyse par transfert de phase inverse peut être utilisée. La synthèse de nouveaux catalyseurs organométalliques solubles dans l eau a donc été envisagée. Ces catalyseurs seront dérivés de cyclodextrine et pourront également assurer le transport du substrat en phase aqueuse par reconnaissance supramoléculaire.For a few years, the priority task for actors of the chemical field has been the design of greener products and greener chemical processes to meet the environmental concerns. Thus, the twelve principles of the green chemistry were set. One of them is to substitute toxic organic solvents for more eco-compatible solvents, such as water, during chemical synthesis. More generally speaking, catalysis plays a significant role in this green chemistry policy as it enables to enhance energy saving, to reduce the quantity of the used compounds and to reduce as well the separation processes by increasing the selectivity. However, the low solubility of organic substrates in water prevents from having profitable yields. To tackle the issue, the catalysis by inverse phase transfer can be used. Therefore, the synthesis of new water soluble organometallic catalysts was considered. These catalysts will be derivates of cyclodextrin and will allow carrying the substrate in aqueous phase by supramolecular recognition.COMPIEGNE-BU (601592101) / SudocSudocFranceF

Ordering of Saturated and Unsaturated Lipid Membranes near Their Phase Transitions Induced by an Amphiphilic Cyclodextrin and Cholesterol

When inserted in membranes of dimyristoyl phosphatidylcholine (DMPC), methylated β-cyclodextrins with one (TrimβMLC) or two (TrimβDLC) lauryl acyl chains grafted onto the hydrophilic cavity exert a "cholesterol-like ordering effect", by straightening the acyl chains in the fluid phase at temperatures near the chain melting transition. This effect may be related to pretransitional events such as the "anomalous swelling" known to occur with saturated phosphatidylcholine membranes. To investigate this model, order profiles and bilayer thicknesses of DMPC and unsaturated 1-palmitoyl-2-oleoyl-phosphatidylcholine (POPC) membranes containing amphiphilic cyclodextrins or cholesterol were determined by deuterium NMR. The pure lipid membranes display both a qualitatively similar chain ordering upon cooling in the fluid phase, more important at the chain extremity, which gets more pronounced near their fluid-to-gel transitions. Both membranes show a bilayer thickness increase by ∼0.5 Å just above their transition, as observed previously with saturated phosphatidylcholines of various chain lengths. Membrane-insertion of 5% TrimβMLC or cholesterol induces an important ordering of the DMPC acyl chains just above the transition, which is also more pronounced at the chain extremity. There is an additional increase of the bilayer thickness, most probably due to a deep insertion of these amphiphilic molecules, facilitated by increased bilayer softness in the anomalous swelling regime. These effects are more important with TrimβMLC than with cholesterol. By contrast, no enhanced acyl chain ordering was observed when approaching the transition of TrimβMLC-containing POPC membranes, as a possible consequence of an eventual lack of anomalous swelling in unsaturated lipid membranes. Insertion of higher concentrations of TrimβMLC was found to induce a magnetic orientation of the DMPC membranes in the fluid phase with 10% of this derivative, coupled with the appearance of a broad isotropic component when the concentration is raised to 20%. No membrane orientation or isotropic component was detected with TrimβMLC-containing POPC membranes

A green approach to the synthesis of novel phytosphingolipidyl β-cyclodextrin designed to interact with membranes

This work reports the synthesis of a new family of mono-substituted amphiphilic cyclodextrins using a green methodology. Reactions using greener and safer catalysts with more environmentally friendly purification solvents were performed. Four unreported mono-substituted cyclodextrins bearing a phytosphingolipidyl chain and a fatty acid chain (C10, C12, C14 and C18) were successfully obtained with a promising yield

Étude par RMN de la reconnaissance chirale par des cyclodextrines modifiées

Le mono-3A, 6A-anhydro-cyclomaltohcptaose est un analogue de la β-cyclodextrine présentant une réduction totale de symétrie induisant des propriétés de reconnaissance chirale remarquables. Une étude structurale par RMN a été effectuée sur un complexe d’inclusion formé avec un atropo-isomère, la dothiépine. Cette étude a montré que chaque énantiomère forme un complexe d’inclusion de structure et d’affinité différentes

Substituent effect on redox potential of terephthalate-based electrode materials for lithium batteries

The substituent effect on the redox potential of lithium terephthalate was studied using symmetrical dilithium disubstituted-terephthalates incorporating bromo, methoxy and amino groups. All the terephthalate derivatives have been synthesized and evaluated as anode material for lithium-ion batteries. The electrochemical results revealed an increase in the reduction potential in the case of bromo and methoxy groups and almost the same in the case of amino group compared to unmodified dilithium terephthalate. In addition, a very first tendency between the 13C chemical shifts and FTIR signal of the carbonyl and the reduction potential of the studied disubstituted-terephthalates was formulated. Keywords: Organic anode materials, Substituent effect, Structure-property relationships, Lithium batterie

Enantioselectivity improvement induced by β-cyclodextrin in the NaBH4 reduction of acetophenone through the formation of a three-component inclusion β-cyclodextrin–acetophenone–triethylamine complex

International audienc