References of "Wathelet, Jean-Paul"
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See detailDiallyl disulfides: comparison between classical and microwave-assisted synthesis
DETHIER, Bérénice ULg; Richel, Aurore ULg; Laurent, Pascal ULg et al

in Ioannou, Efstathia; Roussis, Vassilios (Eds.) Trends in Natural Products Research: Abstracts of the Phytochemical Society of Europe (2011)

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See detailCurrent perspectives on microwave-enhanced reactions of monosaccharides promoted by heterogeneous catalysts.
Richel, Aurore ULg; Laurent, Pascal ULg; Wathelet, Bernard ULg et al

in Catalysis Today (2011), 167

Involvment of heterogeneous catalysts as promoters of carbohydrate conversions, in synergy with microwaves as the heating source, is reported. This paper deals with the application of ion-exchange resins ... [more ▼]

Involvment of heterogeneous catalysts as promoters of carbohydrate conversions, in synergy with microwaves as the heating source, is reported. This paper deals with the application of ion-exchange resins, zeolites, clays and metal oxides as convenient mediators for key transformations of carbohydrates. A special emphasis is placed on the use of (doped) mineral supports, in solventless conditions, as clean promoters in combination with microwave dielectric heating. [less ▲]

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See detailMicrowave-assisted conversion of carbohydrates. State of the art and outlook.
Richel, Aurore ULg; Laurent, Pascal ULg; Wathelet, Bernard ULg et al

in Comptes Rendus Chimie (2011), 14

The valorisation of carbohydrates arising from the hydrolysis of renewable feedstocks (i.e. lignocellulosic biomass) is nowadays an area of outmost interest. In this context, the implementation of fast ... [more ▼]

The valorisation of carbohydrates arising from the hydrolysis of renewable feedstocks (i.e. lignocellulosic biomass) is nowadays an area of outmost interest. In this context, the implementation of fast, expeditious and cost-effective methodologies for the modification of these naturally occurring compounds is becoming a prerequisite. In this sense, the application of microwaves has gained progressive attention in laboratories for making a range of high-added value sugars derivatives scaffolds. Advantages of microwaves are numerous and include enhancement of reaction rates and yields, combined to improved regio-, chemo- and anomeric selectivities. Summary: 1. Introduction 2. Chemical transformations of monosaccharides Regioselective hydroxyls protections/deprotections Derivatisation at the anomeric position Other derivatisations Microwave-assisted click chemistry Synergy between microwaves and heterogeneous catalysis Enzymatic modifications of monosaccharides 3. Effect of microwave heating on polysaccharides Hydrolysis and pretreatment of cellulose Derivatisation of cellulose 4. Scale-up of microwave-promoted reactions 5. Conclusions [less ▲]

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See detailSynthesis and Surface-Active Properties of Uronic Amide Derivatives, Surfactants from Renewable Organic Raw Materials
Laurent, Pascal ULg; Razafindralambo, Hary ULg; Wathelet, Bernard ULg et al

in Journal of Surfactants and Detergents (2011), 14(1), 51-63

Short chemical syntheses were developed to produce a new set of surfactants from uronic acids derived from widely available raw material. Three different strategies were used to synthesise uronic amide ... [more ▼]

Short chemical syntheses were developed to produce a new set of surfactants from uronic acids derived from widely available raw material. Three different strategies were used to synthesise uronic amide derivatives, the structures of which were totally characterized by spectrometric methods (IR, MS, 1H-RMN and 13C-RMN). The best one, using an acid chloride as synthetic intermediate, furnished the expected amides as a mixture of anomers in 46 to 58 % global yield. Surface-active properties (CMC, g cmc, Tmax, Amin) of homologous series of uronic acid N-alkylamides from C8 to C18 were also assessed. In general, these sugar-based surfactants exhibited good surface-activities, and appeared as valuable non ionic surfactants compared to Triton X-100, the most well-known non ionic surfactant. Increasing the alkyl chain length influenced the CMC values for both glucuronic and galacturonic N-alkylamide derivatives. The galacturonic N-alkylamides decreased g cmc at slower values than their counterpart's glucuronic N-alkylamides. [less ▲]

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See detailNew insights into the transformation of carbohydrates into platform chemicals
Richel, Aurore ULg; Wathelet, Jean-Paul ULg; Paquot, Michel ULg

Poster (2010, October 14)

The synthesis of furanic compounds from carbohydrates has become exciting in chemistry and in catalysis studies, because it represents one of the major routes for achieving sustainable energy supply and ... [more ▼]

The synthesis of furanic compounds from carbohydrates has become exciting in chemistry and in catalysis studies, because it represents one of the major routes for achieving sustainable energy supply and chemicals production.1 In particular, 5-hydroxymethylfurfural (5-HMF) and 2-furfural (2-F) occupy a pivotal place and are recognised as versatile and multi-functional starting points for the synthesis of a panel of precursors. Microwaves have readily appeared as a powerfull technique for accelerating reaction rates and increasing selectivities in the field of carbohydrate chemistry.3 In particular, their involvment in combination with heterogeneous catalysts have opened new vistas in the production of bio-oxygenated platform chemicals. The state of the art and main outlook of this strategy are reported here. [less ▲]

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See detailTowards the synthesis of mannose derivatives of natural phenolic compounds
Sainvitu, Pauline ULg; Nott, Katherine ULg; Richard, Gaetan ULg et al

Poster (2010, October 14)

The aim of this project is to graft a sugar moiety onto polyfunctional natural phenolic compounds. This should enhance their water solubility. The choice of an adequate sugar such as mannose could provide ... [more ▼]

The aim of this project is to graft a sugar moiety onto polyfunctional natural phenolic compounds. This should enhance their water solubility. The choice of an adequate sugar such as mannose could provide cellular recognition. The synthesis route was first tested on cinnamyl alcohol which is structurally close to the base pattern of natural phenolic compounds. Two compounds are tested to catalyse the glycosilation between cinnamyl alcohol and D-mannose. The first one is an enzyme, the -glucosidase from almond, and the second one is a mineral acid catalyst immobilized on silica. Results show that -glucosidase is able to synthetize cinnamyl mannoside from mannose and cinnamyl alcohol. Furthermore, enzyme-catalyzed route lead to only one product and is so more specific than the chemical route where several products are observed. The obtaining of one product with a unique structure is interesting for the fundamental study of structure-function relationships (Interaction of the product with model membranes by Isothermal Titration Calorymetry and with the Langmuir Trough technique). In a future work, the reaction will be tested with more complex molecules (for example coniferyl alcohol). [less ▲]

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See detailDevelopment of biological control formulations incorporating components of plant origin
Heuskin, Stéphanie ULg; Lorge, Stéphanie; Verheggen, François ULg et al

in Journée Scientifique annuelle de la Société Royale de Chimie: Jeudi 14 octobre 2010, Gembloux Agro-Bio Tech, Université de Liège, Chimie verte (2010, October 14)

Semiochemicals – informative molecules used in insect-insect or plant-insect interactions – have been considered within various integrated pest management IPM strategies. Herein, two sesquiterpenoids: E-β ... [more ▼]

Semiochemicals – informative molecules used in insect-insect or plant-insect interactions – have been considered within various integrated pest management IPM strategies. Herein, two sesquiterpenoids: E-β-farnesene and E-β-caryophyllene have been formulated for their potential properties as aphid enemies attractants. Indeed, E-β-farnesene, the alarm pheromone of many aphid species [1], has also been identified as a kairomone by attracting and inducing oviposition of aphid predators (Episyrphus balteatus De Geer (Diptera: Syrphidae)) [2-5] and by attracting aphid parasitoids (Aphidius ervi Haliday (Hymenoptera: Braconidae)) [6, 7]. E-β-caryophyllene was identified as a potential component of the aggregation pheromone of the Asian ladybird, Harmonia axyridis Pallas [8, 9]. The two products have been purified from essential oils of Matricaria chamomilla L. (Asteraceae) and Nepeta cataria L. (Lamiaceae) [10, 11]. Natural and biodegradable slow-release devices have been investigated in order to deliver these molecules. Moreover, due to their sensitivity to oxidation, the sesquiterpenes needed to be protected. For this purpose, alginate (hydrophilic matrix with low oxygen permeability) was used as polymer for the formulations: the main objective was to hold and deliver semiochemical substances in a controlled way. Consequently, a careful selection of alginates was realised for encapsulation. Formulated beads showed different structural and encapsulation properties depending on factors such as polymer concentration, ionic strength, type and concentration of cross-linker ion,... The gel structure influenced diffusion properties. Alginate formulations were characterized by texturometry and by confocal microscopy in order to observe the distribution of semiochemicals in alginate network. The last step consisted in studying release rate of semiochemicals in laboratory-controlled conditions by adapted trapping and Fast-GC procedures [10,11]. [less ▲]

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See detailSynthèse assistée par Micro-ondes de dérivés d'acides uroniques
Laurent, Pascal ULg; Richel, Aurore ULg; Wathelet, Bernard ULg et al

Poster (2010, October 14)

At the moment, biorefining is increasingly seen as a promising alternative to petrochemical sector since it targets both the replacement of part of petroleum as a source of energy and the development of ... [more ▼]

At the moment, biorefining is increasingly seen as a promising alternative to petrochemical sector since it targets both the replacement of part of petroleum as a source of energy and the development of chemicals from the biomass, such as detergents, phytopharmaceutics, solvents, plastics, etc. The valorisation of carbohydrates arising from the hydrolysis of renewable feedstocks is therefore an area of outmost interest. In this context, uronic acids such as glucuronic acid (GlcA) or galacturonic acid (GalA) derived from widely available raw material such as hemicellulose or pectins represent important biocompatible and bioresorbable starting material. The quest of highly effective, environmentally friendly and straightforward chemical strategies to transform totally O-unprotected uronic acids into high valuable materials remains actually a particularly challenging task. A new strategy enabling the quantitative “one-pot” production of water-soluble monosubstituted D-glucofuranosidurono-6,3-lactones from unprotected D-glucuronic acid (D-GlcA) involving microwaves and an inexpensive siliceous-based promoter will be described. The use of a heterogeneous acid catalytic systems consisting of sulfuric acid impregnated onto silica (H2SO4/SiG60) or onto carbon (H2SO4/C), offers a green alternative to unrecyclable liquid sulfuric acid and permit the developpment of a truly eco-friendly green process, as these supported acids were readily separated from liquid products, without neutralization, by decantation or filtration, thus minimizing energy consumption and wastes. Faced with environmental concerns, this solventless methodology offers attractive features, including short reaction times, high yields and easy set-up and workup. [less ▲]

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See detailCARBOHYDRATE-BASED SURFACTANTS FOR FORMING AND STABILIZING COLLOIDAL SYSTEMS AS EMULSIONS AND FOAMS
Razafindralambo, Hary ULg; Blecker, Christophe ULg; Richel, Aurore ULg et al

in Abstracts book of 5th edition of world congress on emulsions (2010, October 12)

Carbohydrate-based surfactants (CBS) constitute a class of amphiphilic molecules with particular and common interests. These surface-active compounds can be produced from the most abundant renewable ... [more ▼]

Carbohydrate-based surfactants (CBS) constitute a class of amphiphilic molecules with particular and common interests. These surface-active compounds can be produced from the most abundant renewable materials allowing large product concept possibilities, and may occur in a large structural range with one or more hydrophilic head groups and hydrophobic chains with various linkers/spacers, thanks to numerous reactive functional groups in their basic structure. It is then possible to design a quasi-unlimited number of new compounds by (bio)-synthesis from various raw materials. This structural diversity can generate a wide range of properties, which could be developed in food and non-food applications. Our challenge is now to find out the most suitable molecular structures for the post-development of CBS, mainly for colloidal systems like emulsion, foam, and suspension. A pre-screening of the dynamic and equilibrium interfacial tensions and interfacial rheology properties of various CBS prepared by chemical, enzymatic, or chemo-enzymatic synthesis routes from the derivatives of bio-renewable substrates is carried out. Then, the characterization of emulsifying and foaming properties of pre-selected molecules is performed. These investigations are completed by the characterization of thermal properties of liquid suspensions and powders. Homologous series of two derivative compounds of glucuronic and galacturonic acids with mono- or bicatenar hydrophobic chains and different linkages (linear or cyclic ester, amide) have been chosen as CBS starting compounds. These were full characterized by spectroscopic techniques (RMN, SM, IR). The effect of the hydrophobic chain length and number, polar head group, and the linker on whole properties investigated is easily deduced. [less ▲]

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See detailBiological control formulations incorporating essential oils' components
Heuskin, Stéphanie ULg; Lorge, Stéphanie; Wathelet, Jean-Paul ULg et al

in Lochynski, Stanislaw; Wawrzenczyk, Czeslaw (Eds.) 41th International Symposium on Essential Oils - Programme and Book of Abstracts (2010, September)

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See detailOptimisation of slow-release formulations as biological control devices
Heuskin, Stéphanie ULg; Lorge, Stéphanie; Debatty-Mestdagh, Michelle et al

Poster (2010, May 05)

E-β-Farnesene, the alarm pheromone of many aphid species and β-caryophyllene, recently identified as one of the possible component of the aggregation pheromones of the Asian ladybeetles Harmonia axyridis ... [more ▼]

E-β-Farnesene, the alarm pheromone of many aphid species and β-caryophyllene, recently identified as one of the possible component of the aggregation pheromones of the Asian ladybeetles Harmonia axyridis Pallas, are considered as two sesquiterpenes attractive for aphids’ predators and parasitoids, Epysirphus balteatus De Geer and Aphidius ervi Haliday, respectively. In the present research, alginate gel beads formulations were optimised as semiochemical slow-release devices. The formulations were evaluated in terms of volatiles release capacity, protection efficiency of sesquiterpenes against oxidation, and biological activity towards Epysirphus balteatus and Aphidius ervi. Moreover, the sesquiterpenes used in the formulations were obtained from natural matrices. Indeed, they were purified by flash chromatography fractionation of essential oils of Matricaria chamomilla L. and Nepeta cataria L., for obtaining E-β-farnesene and β-caryophyllene, respectively. The purities of the fractions were determined by means of a fast GC analytical method optimised for a good resolution of terpenes in less than five minutes. The experiments can conclude that the alginate gel beads formulations are efficient as biological control devices considering the results obtained with the various biological tests led on predators and parasitoids. Moreover, the sesquiterpenes are more protected when formulated in alginate beads than without formulation. The devices allow also a slow-release of semiochemicals during a long time (at least 40 days) depending on physico-chemical parameters (temperature, relative humidity). A mathematical modelisation of semiochemicals release is presently in study. [less ▲]

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See detailInfluence de l'ajout de co-solvant pour l'estérification du D-mannose et de l'acide D-glucuronique assistée par les lipases
Richard, Gaetan ULg; Brognaux, Alison ULg; Nott, Katherine ULg et al

Poster (2010, May)

En parallèle à la production de biocarburant, le second objectif du bioraffinage est la transformation des sucres issus de l’hydrolyse de la lignocellulose en produits d’intérêt, qui se substitueront aux ... [more ▼]

En parallèle à la production de biocarburant, le second objectif du bioraffinage est la transformation des sucres issus de l’hydrolyse de la lignocellulose en produits d’intérêt, qui se substitueront aux produits de la vie courante issus du pétrole. L’une des voies de valorisation envisageable est la synthèse de molécules amphiphiles par greffage de chaînes grasses sur le sucre. Ces composés trouveraient alors des applications dans de très nombreux domaines utilisant les tensioactifs (alimentaire, détergence, peinture,…) . Dans le cadre du programme d’excellence TECHNOSE et du projet d’Action de Recherche Concertées SUPERZYM, deux sucres ont été testés : un polyol, le D-mannose, et un sucre acide, l’acide D-glucuronique. Afin de conférer un caractère amphiphile à la molécule, les lipases ont été utilisées en tant qu’outils d’estérification. Ces triglycérides hydrolases sont en effet capables de catalyser ce type de réaction, et de nombreux exemples dans la littérature démontrent le fort potentiel industriel de ces enzymes , . L’estérification du D-mannose et de l’acide D-glucuronique a donc été mise en œuvre en présence de la lipase de Candida antarctica B (Novozyme 435). La réaction est effective, mais l’ajout de co-solvants tels que la pyridine ou le DMSO améliore les vitesses initiales et les rendements de la réaction. Ces améliorations seront discutées et comparées sur ce poster. [less ▲]

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See detailMicrowave-assisted conversion of carbohydrates. State of the art and outlook.
Richel, Aurore ULg; Laurent, Pascal ULg; Wathelet, Bernard ULg et al

Conference (2010, May)

The valorisation of carbohydrates arising from the hydrolysis of renewable feedstocks (i.e. lignocellulosic biomass) is nowadays an area of outmost interest. In this context, the implementation of fast ... [more ▼]

The valorisation of carbohydrates arising from the hydrolysis of renewable feedstocks (i.e. lignocellulosic biomass) is nowadays an area of outmost interest. In this context, the implementation of fast, expeditous and cost-effective methodologies for the modification of these naturally occurring compounds is becoming a prerequisite. In this sense, the application of microwaves has gained progressive attention in laboratories for making a range of high-added value sugars derivatives scaffolds. Its advantages are numerous and include enhacement of reaction rates and yields combined to improved regio-, chemo- and anomeric selectivities. Since the first publications of Gedye et Giguere in 1986, the use of microwave has progressively emerged as a popular non conventional heating source in the field of organic synthesis.1 Nevertheless, its application in the area of carbohydrate chemistry is less documented.2, 3 Although research in this field is still in its infancy, recourse to microwaves often provides, with remarkable yields and atom efficiency, new carbohydrate-based structures that are not easily available by any another means (or only via painstaking multi-step protocols). This communication proposes therefore selected, recent and non exhaustive illustrations of the application of microwaves to promote famous carbohydrates “model” reactions. The scale-up of such microwave-assisted reactions is also presented. [less ▲]

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See detailMicrowave – assisted synthesis of carbohydrate compounds, focus on uronic acid derivatives.
Laurent, Pascal ULg; Richel, Aurore ULg; Wathelet, Bernard ULg et al

Poster (2010, May)

At the moment, biorefining is increasingly seen as a promising alternative to petrochemical sector since it targets both the replacement of part of petroleum as a source of energy and the development of ... [more ▼]

At the moment, biorefining is increasingly seen as a promising alternative to petrochemical sector since it targets both the replacement of part of petroleum as a source of energy and the development of chemicals from the biomass, such as detergents, phytopharmaceutics, solvents, plastics, etc. The valorisation of carbohydrates arising from the hydrolysis of renewable feedstocks is therefore an area of outmost interest. In this context, uronic acids such as glucuronic acid (GlcA) or galacturonic acid (GalA) derived from widely available raw material such as hemicellulose or pectins represent important biocompatible and bioresorbable starting material. The quest of highly effective, environmentally friendly and straightforward chemical strategies to transform totally O-unprotected uronic acids into high valuable materials remains actually a particularly challenging task. A new strategy enabling the quantitative “one-pot” production of water-soluble monosubstituted D-glucofuranosidurono-6,3-lactones from unprotected D-glucuronic acid (D-GlcA) involving microwaves and an inexpensive siliceous-based promoter will be described. The use of a heterogeneous acid catalytic systems consisting of sulfuric acid impregnated onto silica (H2SO4/SiG60) or onto carbon (H2SO4/C), offers a green alternative to unrecyclable liquid sulfuric acid and permit the developpment of a truly eco-friendly green process, as these supported acids were readily separated from liquid products, without neutralization, by decantation or filtration, thus minimizing energy consumption and wastes. Faced with environmental concerns, this solventless methodology offers attractive features, including short reaction times, high yields and easy set-up and workup. [less ▲]

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See detailLipase-assisted synthesis of potential bio-based surfactants starting from lignocellulosic carbohydrates
Richard, Gaetan ULg; Nott, Katherine ULg; Paquot, Michel ULg et al

Poster (2010, April)

Surfactants constitute an important class of compounds with a lot of applications, especially in the food and beverage industries (emulsion forming and stabilization, antiadhesive and antimicrobial ... [more ▼]

Surfactants constitute an important class of compounds with a lot of applications, especially in the food and beverage industries (emulsion forming and stabilization, antiadhesive and antimicrobial activities)1. With the prospect of synthesising new active compounds, white biotechnology offers efficient tools. Indeed, the use of enzymes as biocatalysts provides an interesting synthetic route in comparison to the chemical way that often requires high reaction temperatures and suffers from a lack of specificity, resulting in complex mixtures. Among all the biocatalysts available, lipases represent a class of industrial interest 2,3. In parallel, the starting material is also an important parameter : due to the depletion of petroleum reserves, its ever increasing price and various environmental aspects, the use of renewable or biomass resources is inevitable. Within the frame of a biorefinery project, we focused on the lipase-assisted modification of uronic acids. These carbohydrates can be obtained from lignocellulosic material, and, in the presence of fatty alcohols, the Candida antarctica lipase B catalyses the synthesis of amphiphilic compounds. Owing to the initial conditions used and the addition of co-solvents, we optimized the synthesis of these bio-based potential surfactants, and obtained a panel of various structures depending to the acyl acceptor used. The poster will present the details of these syntheses. [less ▲]

Detailed reference viewed: 21 (1 ULg)