Glycosidation of fructose-containing disaccharides using MCM-41 material as the catalyst

Catalytic Upgrading of Biomass-Derived Sugars with Acidic Nanoporous Materials: Structural Role in Carbon-Chain Length Variation

Shifting from petroleum-based resources to inedible biomass for the production of valuable chemicals and fuels is one of the significant aspects in sustainable chemistry for realizing the sustainable development of our society. Various renowned biobased platform molecules, such as 5-hydroxymethylfurfural, furfural, levulinic acid, and lactic acid, are successfully accessible from the transformation of biobased sugars. To achieve the specific reaction routes, heterogeneous nanoporous acidic materials have served as promising catalysts for the conversion of bio-sugars in the past decade. This Review summarizes advances in various nanoporous acidic materials for bio-sugar conversion, in which the number of carbon atoms is variable and controllable with the assistance of the switchable structure of nanoporous materials. The major focus of this Review is on possible reaction pathways/mechanisms and the relationships between catalyst structure and catalytic performance. Moreover, representative examples of catalytic upgrading of biobased platform molecules to biochemicals and fuels through selective C-C cleavage and coupling strategies over nanoporous acidic materials are also discussed.

Synthesis of novel perfluoroalkylglucosides on zeolite and non-zeolite catalysts

Perfluoroalkylglucosides comprise a very important class of fluorine-containing surfactants. These compounds can be synthesized by using the Fisher reaction, starting directly from glucose and the required perfluoroalcohols. We wish to report on the use of zeolite catalysts of different structure and composition for the synthesis of perfluoroalkylglucosides when using glucose and 1-octafluoropentanol as substrates. Zeolites of different pore architecture have been chosen (ZSM-5, ZSM-12, MCM-22 and Beta). Zeolites were characterized by XRD, nitrogen sorption, scanning electron microscopy (SEM) and solid-state ²⁷Al MAS NMR spectroscopy. The activity of the zeolite catalysts in the glycosidation reaction was studied in a batch reactor at 100 °C below atmospheric pressure. The performance of zeolites was compared to other catalysts, an ion-exchange resin (Purolite) and a montmorillonite-type layered aluminosilicate. The catalytic performance of zeolite Beta was the highest among the zeolites studied and the results were comparable to those obtained over Purolite and montmorillonite type catalysts.

A nanospherical ordered mesoporous Lewis acid polymer for the direct glycosylation of unprotected and unactivated sugars in water

The design of robust solid catalysts which can selectively synthesize highly functionalized carbohydrate derivatives from unprotected and unactivated simple sugars in water is an outstanding challenge. Herein we describe the preparation of a novel nanospherical ordered mesoporous Lewis acid polymer (Sc(OTf)2-NSMP) by functionalizing the mesoporous phenol-formaldehyde polymer framework with scandium triflate groups. In the C-glycosylation reaction between D-glucose and dimedone with the Sc(OTf)2-NSMP catalyst, the conversion was 99% and the yield of xanthone-C-glucoside reached 92% after 2 days, which exceeded the previous best results. It was shown that other xanthone glycosides can be obtained from various sugars with moderate to good yields. Furthermore, the catalyst can be easily recovered and reused at least seven times without loss of catalytic activity.

Alkali Metal Cationization of Alkyl Glucosides under Electrospray Ionization Conditions

Alkyl glucosides have been studied by electrospray ionization mass spectrometry. The effect of the hydrophobic and the hydrophilic parts of these compounds on the stability of [M + Na]+ ions has been evaluated by mass spectra at growing cone voltages. The longer the hydrophobic or the hydrophilic part, the higher the stability of these ions. It has been also found that solvent used affects the abundances of [M + Na]+ ions. In order to check if the radii of alkali metal ions influence the stability of their adducts with the compounds studied, the mass spectra have been recorded for solution containing lithium and potassium ions. The cations of smaller radius form more stable adducts, especially with the compounds having longer hydrophobic parts.

Biologically-inspired peptide reagents for enhancing IMS-MS analysis of carbohydrates

The binding properties of a peptidoglycan recognition protein are translated via combinatorial chemistry into short peptides. Non-adjacent histidine, tyrosine, and arginine residues in the protein's binding cleft that associate specifically with the glycan moiety of a peptidoglycan substrate are incorporated into linear sequences creating a library of 27 candidate tripeptide reagents (three possible residues permutated across three positions). Upon electrospraying the peptide library and carbohydrate mixtures, some noncovalent complexes are observed. The binding efficiencies of the peptides vary according to their amino acid composition as well as the disaccharide linkage and carbohydrate ring-type. In addition to providing a charge-carrier for the carbohydrate, peptide reagents can also be used to differentiate carbohydrate isomers by ion mobility spectrometry. The utility of these peptide reagents as a means of enhancing ion mobility analysis of carbohydrates is illustrated by examining four glucose-containing disaccharide isomers, including a pair that is not resolved by ion mobility alone. The specificity and stoichiometry of the peptide-carbohydrate complexes are also investigated. Trihistidine demonstrates both suitable binding efficiency and successful resolution of disaccharides isomers, suggesting it may be a useful reagent in IMS analyses of carbohydrates.

Thermotropic liquid crystalline glycolipids

Are the liquid crystalline properties of the materials of living systems important in biological structures, functions, diseases and treatments? There is a growing consciousness that the observed lyotropic, and often thermotropic liquid crystallinity, of many biological materials that possess key biological functionality might be more than curious coincidence. Rather, as the survival of living systems depends on the flexibility and reformability of structures, it seems more likely that it is the combination of softness and structure of the liquid-crystalline state that determines the functionality of biological materials. The richest sources of liquid crystals derived from living systems are found in cell membranes, of these glycolipids are a particularly important class of components. In this critical review, we will examine the relationship between chemical structure and the self-assembling and self-organising properties of glycolipids that ultimately lead to mesophase formation.

A Model for the Structure of MCM-41 Incorporating Surface Roughness

The surface area of MCM-41 mesoporous silica, estimated by several models in the literature, is significantly less than the value derived from BET analysis of nitrogen adsorption at 77.4 K. In the past, the difference has been attributed to several reasons including the errors involved in the BET analysis of the multilayer-capillary condensation region and the heterogeneity of the walls. In the present work, we present an alternate model of MCM-41 based on molecular simulations that gives surface area values that are in closer agreement to those determined by experiment. The model incorporates bulk heterogeneity of the material, surface hydroxyls, and most importantly, physical deformations or indentations of the pore surface. The model predicts small-angle X-ray diffraction (XRD) and wide-angle X-ray scattering (WAXS) results that are consistent with experimental data as well as surface areas and pore volumes that compare favorably with published experimental results. The simulation results are consistent with the hypothesis that the interstitial space in MCM-41 is relatively amorphous despite the regular arrangement of the mesopores. The surface roughness associated with the amorphous structure increases the surface area beyond the nominal value produced by assuming smooth cylindrical pores.