Gwladys Pourceau

Chapter 11:Anionic oligosaccharides: synthesis and applications

Anionic oligosaccharides are largely involved in physiological and pathological processes. The controlled production of these biomolecules is crucial for the comprehension of the biological mechanisms in which they are involved, but it is still challenging and troublesome. This chapter reviews the recent protocols (since 2008) described in literature for the obtaining of anionic oligosaccharides by de novo synthesis and by polysaccharide depolymerisation. An overview on recent applications is also presented.

On the chiroptical properties of Au(I)–thiolate glycoconjugate precursors and their influence on sugar-protected gold nanoparticles (glyconanoparticles)

Chiral gold nanoparticles passivated with glycoconjugates were prepared. By extensive washing, they lost their chiroptical activity, whereas highly luminescent compounds isolated from the washing reproduced the original ellipticity. A systematic characterization of these compounds, Au(I) precursors and glyconanoparticles allowed us to unravel the origin of the observed chiroptical activity.

Efficient synthesis of glycosylamines in solventless conditions promoted by mechanical milling

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.

Predictive Model Based on the Evidence Theory for Assessing Critical Micelle Concentration Property

In this paper, we introduce an uncertain data mining driven model for knowledge discovery in chemical database. We aim at discovering relationship between molecule characteristics and properties using uncertain data mining tools. In fact, we intend to predict the Critical Micelle Concentration (CMC) property based on a molecule characteristics. To do so, we develop a likelihood-based belief function modelling approach to construct evidential database. Then, a mining process is developed to discover valid association rules. The prediction is performed using association rule fusion technique. Experiments were conducted using a real-world chemical databases. Performance analysis showed a better prediction outcome for our proposed approach in comparison with several literature-based methods.

Nitroxide supported on nanometric metal oxides as new hybrid catalysts for selective sugar oxidation

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.

Catalytic Synthesis of a New Series of Alkyl Uronates and Evaluation of Their Physicochemical Properties

Large quantities (>3 g) of a new series of alkyl uronates were synthesized in two steps from commercial methyl hexopyranosides. Firstly, several tens of grams of free methyl α-d-glucopyranoside were selectively and quantitatively oxidized into corresponding sodium uronate using 2,2,6,6-tetramethyl-1-piperidinyloxy free radical (TEMPO)-catalyzed oxidation. Hydrophobic chains of different length were then introduced by acid-mediated esterification with fatty alcohols (ethyl to lauryl alcohol) leading to the desired alkyl glucuronates with moderate to good yields (49%–72%). The methodology was successfully applied to methyl α-d-mannopyranoside and methyl β-d-galactopyranoside. Physicochemical properties, such as critical micelle concentration (CMC), equilibrium surface tension at CMC (γcmc), solubility, and Krafft temperature were measured, and the effect of structural modifications on surface active properties and micelle formation was discussed.