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Mise au point de nouvelles méthodes éco-compatibles de modifications chimiques régio et stéréosélectives de saccharides (méthodes d'activation alternatives, catalyse ...)
Synthèse de molécules d'intérêt pour des applications phytosanitaires ou médicales
Mechanosynthesis and Polymerization of Biosourced Styrene Derivatives Based on Building Blocks of Lignin |
Gold-Catalyzed Oxidative Transformation of Free Sugars into Biobased Platform Molecules |
Fast and Efficient Mechanosynthesis of Aldonamides by Aminolysis of Unprotected Sugar Lactones |
Synthesis and interfacial properties of new 6-sulfate sugar-based anionic surfactants |
Physicochemical, foaming and biological properties of lowly irritant anionic sugar-based surfactants |
Insight on the Contribution of Plasmons to Gold-Catalyzed Solar-Driven Selective Oxidation of Glucose under Oxygen |
Nitroxide-Grafted Nanometric Metal Oxides for the Catalytic Oxidation of Sugar |
Impact of the chemical structure on amphiphilic properties of sugar-based surfactants: A literature overview |
First Sustainable Aziridination of Olefins Using Recyclable Copper-Immobilized Magnetic Nanoparticles |
Lactose derivatives as potential inhibitors of pectin methylesterases |
Photocatalyzed Transformation of Free Carbohydrates |
Nitroxide supported on nanometric metal oxides as new hybrid catalysts for selective sugar oxidation |
Gold Catalysis and Photoactivation: A Fast and Selective Procedure for the Oxidation of Free Sugars |
Imidazolium-based titanium substrates against bacterial colonization |
Improvement of Gold-Catalyzed Oxidation of Free Carbohydrates to Corresponding Aldonates Using Microwaves |
Catalytic Synthesis of a New Series of Alkyl Uronates and Evaluation of Their Physicochemical Properties |
On the chiroptical properties of Au(i)–thiolate glycoconjugate precursors and their influence on sugar-protected gold nanoparticles (glyconanoparticles) |
Efficient synthesis of glycosylamines in solventless conditions promoted by mechanical milling |
Chapter 11 Anionic oligosaccharides: synthesis and applications |
Finding and developing new biosourced materials that can compete with the current petro-sourced ones are a top priority in order to transition to a more sustainable society. Although the preparation of biosourced polyesters or polyamides is quite well described, finding biosourced and sustainable alternatives to petro-sourced polystyrene is still challenging. Herein, we report the synthesis of polystyrenes prepared in three steps from vanillin, 4-hydrobenzaldehyde, and syringaldehyde, compounds that can be obtained through lignin depolymerization under oxidative conditions. The synthesis involves the conversion of these biosourced platforms into polymerizable styrene derivatives through a methylation of the hydroxyl group followed by an olefination of the aldehyde function. The monomers were first synthesized under conventional conditions using solvents. Then, the synthesis was improved from the sustainability point of view by using a ball mill under solventless conditions, generating much less waste in the process. The three monomers were then converted into biosourced homopolymers through free radical polymerization in bulk, providing functional polystyrene derivatives with thermal properties comparable to those of common petro-sourced polystyrene.
Due to their easy conversion into high-added value products, sugar lactones and their derivatives are very attractive biobased platform molecules. Yet, conventional transformation of free sugars into such activated compounds is not so handy: a multistep procedure requiring protection/oxidation/lactonization-esterification/deprotection is often necessary. We report herein a procedure allowing one to rapidly and efficiently form lactones/esters directly from free sugars under mild conditions, catalyzed with a small amount (0.36 mol %) of recyclable gold nanocatalyst under oxygen atmosphere. The conditions were optimized using galactose as a model, quantitatively and selectively affording 1,4-galactonolactone in 2 h at room temperature. The procedure was then successfully applied to a variety of hexoses and pentoses leading to excellent conversion (>86%). Due to the equilibrium between lactone regioisomers and ester forms, a mixture of 1,4-lactone, 1,5-lactone and methyl ester can be generally obtained depending on the sugar series. A subsequent reaction of the crudes with benzylamine leads to a total conversion of lactones/esters into corresponding amides, confirming the efficiency of the procedure and paving the way to a one-pot transformation of free sugars into high added value sugar-based derivatives. Based on NMR and ESR analyses, a mechanism of the reaction involving CH3O• radical species seems to be taking shape.
Three families of anionic sugar-based surfactants bearing a sulfate functional group on the primary position of a monosaccharide were synthesized and their physicochemical properties were compared. The first family corresponds to 6-sulfate derivatives of commercially available octa- and dodecyl β-D-gluco- and galactopyranosides. The second and the third families contain an amide linker between the sulfated monosaccharide (galactose, glucose or xylose) and the hydrophobic alkyl chain. Twelve of the as-synthesized anionic glycolipids, including nine novel sulfated compounds, were investigated for their surface activity at the air/liquid interface and for their self-assembling properties. These sugar-based surfactants show surface properties similar to those of commercial anionic surfactants (SDS and SLES) with good ability to reduce surface tension. The obtained results confirm the interest in these new bio-based molecules for potential substitution of anionic surfactants in various formulations.
Surface-active compounds derived from biomass, especially sugar-based amphiphiles, have received wide attention regarding their biodegradability, low toxicity and ecological acceptability. Compared to nonionic sugar-based surfactants, the anionic ones show significantly better solubility, higher surface activity and foaming performance. Thus they are largely used in personal care formulations and many technological applications. However, anionic surfactants are well known to induce skin and eye irritation. In this study, three sugar-based anionic surfactants, bearing a lipidic chain grafted to the anomeric position of a monosaccharide (glucose or xylose) and a sulfate group on the primary hydroxyl, were synthesized: 6-O-sulfo-N-(β-d-glucopyranosyl) dodecanamide (GlcNC12S), N-dodecyl-6-O-sulfo-d-gluconamide (GlcCC12S) and N-dodecyl-6-O-sulfo-d-xylonamide (XylCC12S). These molecules were investigated in details for their self-assembling behavior, foaming properties and biological effects. All their properties were compared to those of two commercially available anionic surfactants, sodium laureth sulfate (SLES) and sodium dodecylsulfate (SDS). Results revealed that the three anionic glycolipids show surface properties and foaming behavior comparable to those of SDS. Furthermore, their cytotoxic and irritation potentials are significantly lower compared to commercial molecules, which make these renewable molecules potential candidates for replacement of petroleum-based compounds.
A new series of ([2,2,6,6-tetramethylpiperidin-1-yl]oxy) (TEMPO) catalysts supported on nanometric metal oxides (TiO2, AlO2, CeO2) and their efficiency for sugar oxidation are herein described. The preparation of such hybrid catalysts was carried out by modification of a metal oxide surface with a monolayer of phosphonic linker bearing a TEMPO radical. All prepared catalysts were carefully characterized by diffuse reflectance Fourier-transform infrared spectroscopy, thermogravimetric analysis, X-ray diffraction, and transmission electron microscopy. The efficiency of these new hybrid TEMPO supported materials for sugar oxidation was evaluated on methyl α-d-glucoside, as a model carbohydrate. The three hybrid catalysts showed high selectivity, activity, and stability, suggesting a promising potential for rapidly obtaining acid sugar derivatives.
In this review, structure-property trends are systematically analyzed for four amphiphilic properties of sugar-based surfactants: critical micelle concentration (CMC), its associated surface tension (γCMC), efficiency (pC20) and Krafft temperature (TK). First, the impact on amphiphilic properties of the alkyl chain size and the presence of branching and/or unsaturation is investigated. Then, various polar head parameters are explored, such as the degree of polymerization of the sugar unit (mono- or oligosaccharides), the chemical nature of the linker and the sugar configuration. Some systematic comparisons between ethoxylated surfactants and sugar-based surfactants are also carried out. While some structural trends with the impact of alkyl chain length or the polar head size are now well understood, this analysis points out that systematic studies of more specific effects of alkyl chain (e.g. branching, unsaturation, presence of rings, position on the polar head) and polar head (e.g. linker, anomeric configuration, internal stereochemistry, cyclic vs. acyclic sugar residues) were scarcer or not available to date. This work encourages the use of these structural trends in the perspective of developing new bio-based surfactants and their consideration in predictive models. It also highlights the need of further experimental tests to fill remaining gaps notably to explore some specific structural features (such as the introduction of rings in the alkyl chain or the position of the alkyl chain on the polar head) and towards applicative properties (like foaming capacity or wettability).
The discovery of molecules that can inhibit the action of phytopathogens is essential to find alternative to current pesticides. Pectin methylesterases (PME), enzymes that fine-tune the degree of methylesterification of plant cell wall pectins, play a key role in the pathogenicity of fungi or bacteria. Here we report the synthesis of new lactoside derivatives and their analysis as potential PME inhibitors using three plants and one fungal PME. Because of its structure, abundance and reduced cost, lactose was chosen as a case study. Lactoside derivatives were obtained by TEMPO-mediated oxidation of methyl lactoside, followed by an esterification procedure. Three derivatives were synthesized: sodium (methyl-lactosid)uronate, methyl (methyl-lactosid)uronate and butyl (methyl-lactosid)uronate. The inhibition of the plant and pathogen enzyme activities by lactoside derivatives was measured in vitro, showing the importance of the substitution on lactose: methyl (methyl-lactosid)uronate was more efficient than butyl (methyl-lactosid)uronate. These results were confirmed by docking analysis showing the difference in the interaction between lactoside derivatives and PME proteins. In conclusion, this study identified novel inhibitors of pectin remodeling enzymes.
A new series of supported organocatalysts, prepared by a simple method, were used for selective sugar oxidation. This approach is based on the immobilization of a nitroxide derivative through a carboxylic function on nanometric metal oxides (TiO2, Al2O3 and CeO2), allowing the recovery of the catalyst. These hybrid materials were carefully characterized by Diffuse Reflectance FT-IR spectroscopy (DRIFT), ThermoGravimetric Analysis (TGA), X-Ray Diffraction (XRD), Brunauer-Emmet-Teller surface area measurements (B.E.T.), elemental and electrochemical analyses, showing different characteristics and behaviors depending on the nature of the metal oxide used. The activity of the supported nitroxide catalyst was evaluated on methyl α-d-glucoside oxidation, used as model reaction. In all cases, high catalytic activity was highlighted, with up to 25 times less nitroxyl radical required for complete conversion than under homogeneous conditions. The influence of several experimental conditions such as the use of phosphate buffer and recyclability of the catalyst were also investigated.
A fast and efficient methodology for the selective oxidation of sugars into corresponding sodium aldonates is herein reported. Hydrogen peroxide was used as a cheap oxidant and electron scavenger, in the presence of only 0.003-0.006 mol % of gold in basic conditions. Three photocatalysts were studied, namely Au/Al2O3, Au/TiO2 and Au/CeO2, the latter being the most efficient (TOF > 750 000 h-1) and perfectly selective. Only 10 minutes exposition under standard incident sunlight irradiation (A.M.1.5G conditions - 100 mW/cm2) affords total conversion of glucose into the corresponding sodium gluconate. Demonstrating its versatility, this methodology was successfully applied to a variety of oligosaccharides leading to the corresponding aldonates in quantitative yield and high purity (>95%) without any purification step. The photocatalyst was recovered by simple filtration and re-used 5 times leading to the same conversion and selectivity after 10 min of illumination.
Nosocomial infections are often induced by the presence of pathogenic organisms on the surface of medical devices or hospital equipment. Chemical modifications of the surface are recognized as efficient strategies to prevent bacterial adhesion but they may have a negative impact on the material's interaction with living tissues. Here we have developed a photoactivated method for the modification of titanium substrates. A photoinduced technique employing a grafting-onto process has been successfully performed to covalently anchor an imidazolium-derivative siloxane onto titanium surfaces. Imidazolium surfaces showed higher bacteria-repellency performances than native titanium substrates, achieving more than 98% anti-adhesion efficiency against Escherichia coli after 24 h of incubation. In addition, these surfaces allowed for the adhesion and viability of osteoblasts cells without evidence of cytotoxicity.
An efficient microwave-assisted methodology for the oxidation of free carbohydrates to corresponding aldonates is described. Supported gold catalyst, hydrogen peroxide and a mineral base were used to perform the oxidation reaction in water under microwave irradiation. These conditions combined with Au/Al2O3 catalyst allowed to reach in 10 minutes a quantitative conversion of glucose.The catalyst was highly selective and reusable and only 0.004 mol % of gold compared to sugar was used. The reaction was performed using a variety of substrates (mono or oligosaccharides, neutral or acidic sugars) and good to excellent conversion yields and selectivity to corresponding aldonates were obtained. After filtration and freeze-drying, sodium or potassium aldonates were obtained without any purification. Thanks to very high turn-over frequencies (up to 438 000 h-1), this methodology improves significantly the previously described methods for the gold-catalyzed oxidation of carbohydrates.
A mecanosynthesis of glycosylamines under solventless conditions was established. This environmentally friendly approach optimized with L-rhamnose, was investigated using a variety of amines and other carbohydrates. High reaction yields and simple work-up allow the clean and fast synthesis of a variety of glycosylamines and glycosyl-(di)-amines.