Gaëtan MISLIN
Antony Fairbanks
Quehon, L.; Pourceau, G.; Wadouachi, A.
Catalytic transformation of biomass-derived natural resources into valuable compounds is of great interest for sustainable development. Particularly, sugar acids obtained by selective oxidation of carbohydrates are very valuable molecules in many areas such as detergency, medicine (pharmaceuticals), and cosmetics. The choice of a robust and highly selective catalyst for oxidation of the aldehyde function vs. hydroxy groups is crucial for such transformations of polyhydroxy aldehyde compounds. In this respect, gold nanoparticles have been shown to be highly chemoselective, favouring high yields of the desired glyconic acid. Nevertheless, several key parameters from catalyst design to reaction conditions should be considered to perform highly efficient catalytic transformation. This chapter aims at highlighting the influence of catalyst material properties such as nature of the support, gold nanoparticle size or synthetic method, on the one hand, and of reaction parameters (pH, temperature, nature of the oxidant, ratio between carbohydrate and gold etc.) on the other hand. Particular emphasis is also placed on the versatility of the reaction (application to other mono- and oligosaccharides) and on the use of alternative methods for activating these heterogeneous catalysts.
Quéhon, L.; Bil, A.; Sauvage, F.; Wadouachi, A.; Pourceau, G.
The development of eco-compatible and economically competitive methods enabling carbohydrate transformation into high-added value sugar-based derivatives is highly desirable to promote their valorization as petroleum-based chemical alternatives. We propose in this study a one-pot sequential procedure for the synthesis of sugar amides, used in various areas from detergency to medicine, starting from nonprotected abundant carbohydrates. The use of a small amount of a recyclable gold catalyst (0.36 mol % Au, Au/CeO2) is crucial for promoting the oxidative amidation reaction. In the presence of benzylamine, d-xylose (the main monomer of hemicellulose used as a model) was converted into corresponding benzyl xylonamide in 3 h at room temperature under an O2 atmosphere. The optimized conditions were then successfully applied to a series of abundant carbohydrates (glucose, galactose, and maltose) and a wide range of amines, thus demonstrating the procedure’s versatility. It is established as not sugar-dependent while being compatible with various functional groups such as alkene, alkyne, thiol, and hydroxyl. Finally, the greenness of the procedure was assessed by comparing the synthesis of N-decyl-d-xylonamide using four green metrics, underlining lower waste generation, higher atom economy, and more acceptable reaction conditions in terms of environmental impact.
Demeester, A.; Douma, F.; Cousin, R.; Siffert, S.; Pourceau, G.; Wadouachi, A.; Ponchel, A.; Monflier, E.; Noël, S.
Cobalt-aluminum-layered double hydroxides containing carboxymethyl β-cyclodextrin (CMβCD) were synthesized by coprecipitation and evaluated as a cobalt source for the 4-nitrophenol reduction in an aqueous medium. Several physicochemical techniques (XRD, FTIR, TGA) indicated the intercalation of the anionic cyclodextrin without damages to the hydrotalcite-type structure. These lamellar cobalt-aluminum hybrid materials (CoAl_CMβCD) were evaluated in the 4-nitrophenol reduction and showed higher activities in comparison with the CMβCD-free standard material (CoAl_CO3). To rationalize these results, a set of experimental controls going from physical mixtures of CoAl_CO3 with different cyclodextrins to other cobalt-based materials were investigated, highlighting the beneficial effects of both the layered double hydroxide and CMβCD-based hybrid structures. CMβCD also showed a beneficial effect as an additive during the 4-nitrophenol reduction. CoAl_CO3, dispersed in a fresh CMβCD solution could be re-used for five successive cycles without the loss of activity.
Lu, H.; Pourceau, G.; Briou, B.; Wadouachi, A.; Gaudin, T.; Pezron, I.; Drelich, A.
Two series of sugar esters with alkyl chain lengths varying from 5 to 12 carbon atoms, and with a head group consisting of glucose or galactose moieties, were synthesized. Equilibrium surface tension isotherms were measured, yielding critical micellar concentration (CMC) surface tensions at CMC (γcmc) and minimum areas at the air–water interface (Amin). In addition, Krafft temperatures (Tks) were measured to characterize the ability of molecules to dissolve in water, which is essential in numerous applications. As a comparison to widely used commercial sugar-based surfactants, those measurements were also carried out for four octyl d-glycosides. Impacts of the linkages between polar and lipophilic moieties, alkyl chain lengths, and the nature of the sugar head group on the measured properties were highlighted. Higher Tk and, thus, lower dissolution ability, were found for methyl 6-O-acyl-d-glucopyranosides. CMC and γcmc decreased with the alkyl chain lengths in both cases, but Amin did not appear to be influenced. Both γcmc and Amin appeared independent of the ester group orientation. Notably, alkyl (methyl α-d-glucopyranosid)uronates were found to result in noticeably lower CMC, possibly due to a closer distance between the carbonyl function and the head group.
Cano, M. E.; Lindgren, Å.; Rosendahl, J.; Johansson, J.; Garcia-Martin, A.; Galan, M. L.; Kovensky, J.; Chinga-Carrasco, G.
Biomass-derived oligo- and polysaccharides may act as elicitors, i.e., bioactive molecules that trigger plant immune responses. This is particularly important to increase the resistance of plants to abiotic and biotic stresses. In this study, cellulose nanofibrils (CNF) gels were obtained by TEMPO-mediated oxidation of unbleached and bleached kraft pulps. The molecular structures were characterized with ESI and MALDI MS. Analysis of the fine sequences was achieved by MS and MS/MS of the water-soluble oligosaccharides obtained by acid hydrolysis of the CNF gels. The analysis revealed the presence of two families: one corresponding to homoglucuronic acid sequences and the other composed by alternating glucose and glucuronic acid units. The CNF gels, alone or with the addition of the water-soluble oligosaccharides, were tested on Chili pepper (Capsicum annuum). Based on the characterization of the gene expression with Next Generation Sequencing (NGS) of the C. annuum's total messenger RNA, the differences in growth of the C. annuum seeds correlated well with the downregulation of the pathways regulating photosynthesis. A downregulation of the response to abiotic factors was detected, suggesting that these gels would improve the resistance of the C. annuum plants to abiotic stress due to, e.g., water deprivation and cold temperatures.
Production d’hydrogène vert à partir de biomasse lignocellulosique par voie photocatalytique
Profil recherché : Etudiant diplômé d’un M2 chimie (ou en cours) avec un goût prononcé pour le travail à l’interface chimie organique/inorganique et la synthèse à la paillasse. Des connaissances en chimie de la biomasse et/ou en photochimie seraient un plus.
Synthèse de Nouveaux Dérivés de Cyclodextrines Assistée par l’Intelligence Artificielle
Profil recherché : Master 2/ingénieur en chimie, avec une expérience en chimie organique ou chimie supramoléculaire. - forte motivation à la fois pour la synthèse organique et la caractérisation physico-chimique des molécules (RMN et SM). Compétences: - bonnes connaissances chimie moléculaire. - maîtrise des techniques de caractérisation des molécules organiques.
Michalska-Walkowiak, J.; Sn Antonio, E.; Coumes, F.; Rieger, J.; Terrasson, V.; Pourceau, G.; Wadouachi, A.; Jeux, V.
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.
Khanchouch, T.; Vallin, A.; Alali, U.; Benazza, M.; Abidi, R.; Bonnet, V.
Abstract Type 2 diabetes mellitus is a metabolic dreadful disease caused by an uncontrolled glucose level in the bloodstream, particularly high after a meal. Inhibitors of glucosidases, involved in the digestion of carbohydrates, can regulate this post-prandial increase in glucose concentration. The traditional drugs act as competitive inhibitors of both pancreatic α-amylase and α-glucosidases and this unselective inhibition is behind severe gastrointestinal side effects related to the concomitant inhibition of α-amylase. We described herein some perglycosylated cyclodextrins as efficient and selective inhibitors of α-glucosidase with low micromolar IC50 (3.64-7.98 μM) compared to the acarbose (IC50 212 μM), clinically used for patients suffering from type 2 diabetes. On the other hand, they do not inhibit α-amylase (IC50>500 μM). Structure/activity relationship rationalization suggests multiple interactions between the described inhibitors and α-glucosidase, which support the existence of both active site and allosteric interactions.
Synthèse de matériaux multifonctionnels basés sur les carbohydrates pour le développement de l’énergie durable, la santé et l’environnement
Profil recherché : Titulaire d’un Master en chimie organique ou en chimie des matériaux. Connaissances indispensables en caractérisation de molécules (RMN, spectrscopie, etc.). 1) Gout pour l’expérimentation 2) Travail en équipe 3) Rigueur et soin expérimental et dans le traitement des données 4) Maîtrise de l'anglais lu, écrit et parlé 5) Aptitudes rédactionnelles et orales français/anglais
Synthèse de matériaux fonctionnels basés sur les carbohydrates pour le développement de l’énergie durable, la santé et l’environnement
Profil recherché : Titulaire d’un Master en chimie organique ou en chimie des matériaux. Connaissances indispensables en caractérisation de molécules (RMN, spectrscopie, etc.). 1) Gout pour l’expérimentation 2) Travail en équipe 3) Rigueur et soin expérimental et dans le traitement des données 4) Maîtrise de l'anglais lu, écrit et parlé 5) Aptitudes rédactionnelles et orales français/anglais
