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The boronic acid functionalization metal-organic frameworks (MOFs), as unique boronate affinity adsorbents, have desired specific molecular affinity for the separation and enrichment of cis-diol-compounds. Herein, the boronic acid functionalized Zn-based MOF adsorbent (MOF-BA) was synthesized through a simple one-step microwave method and used for the recognition and isolation of steviol glycosides (SGs). This MOF-BA exhibits the same spherical structure and isostructure with the parent framework composed only of the primitive ligand as verified by SEM and XRD characterization. It was confirmed that changing the ratio of ligands could achieve the adjustability of the boron content in the framework. At the same time, the MOF-BA-1.0 showed a suitable pore size (4.69 nm), and the presence of boric acid functional groups showed favorable selectivity for stevioside (STV). The static adsorption results showed that adsorption performances of rebaudioside A (RA) and STV from crude sugar solution (5.0 mg [mL.sup.-1], pH 8) on MOF-BA-1.0 were investigated at 303 K for 15 h. The adsorption capacities for STV and RA were 42.93 mg [g.sup.-1] and 22.96 mg [g.sup.-1], respectively, and the adsorption selectivity ([[alpha].sub.STV/RA]) reached 4.35. The adsorption isotherm and kinetic data of MOF-BA-1.0 for RA and STV obeyed the Langmuir isotherm model and pseudo second order kinetic model, respectively. The study demonstrated that MOF-BA-1.0 adsorbent could be used as a potential adsorbent to purify the active ingredients of stevia and obtain a high concentration of RA products. Key words: boronic acid functionalized metal organic framework (MOF-BA), separation, stevioside, rebaudioside A. Les réseaux métallo-organiques (MOF, metal-organic frameworks) fonctionnalisés par un acide boronique, employés comme adsorbants possédant une affinité pour un boronate en particulier, présentent une affinité moléculaire spécifique qui est souhaitable pour effectuer la séparation et l'enrichissement des composés cis-diol. Dans le présent article, nous avons synthétisé un adsorbant consistant en un MOF à base de Zn fonctionnalisé par un acide boronique (MOF-BA) au moyen d'une méthode simple en une étape, fondée sur les micro-ondes, et nous avons utilisé cet adsorbant pour effectuer la reconnaissance et l'isolation des glycosides du stéviol (GS). Ce MOF-BA présente la même structure sphérique et isostructure que le MOF parent, qui se compose uniquement du ligand primitif, tel que le confirme la caractérisation par microscopie électronique à balayage (MEB) et par diffraction des rayons (DRX). Nous avons démontré qu'il est possible de moduler la teneur du bore dans le MOF en variant le rapport des ligands. Par ailleurs, le MOF-BA-1.0 présentait une taille de pores appropriée (4,69 nm), et la présence de groupes fonctionnels àbase d'acide borique a conféré à ce composé une sélectivité favorable pour le stévioside (STV). Les performances d'adsorption statique sur le MOF-BA-1.0 du rébaudioside A (RA) et du stévioside (STV) dans une solution de sucre brut (5,0 mg [mL.sup.-1], pH 8) ont été évaluées à 303 K pendant 15 h. Les résultats ont montré que la capacité d'adsorption du STV et du RA était respectivement de 42,93 mg [g.sup.-1] et de 22,96 mg [g.sup.-1], et que la sélectivité d'adsorption ([[alpha].sub.STV/RA]) atteignait 4,35. L'isotherme d'adsorption et les données cinétiques du MOF-BA-1.0 pour l'adsorption du RA et du STV obéissaient au modèle de l'isotherme de Langmuir et au modèle cinétique de pseudo-second ordre, respectivement. L'étude a permis de montrer que le MOF-BA-1.0 pouvait éventuellement servir d'adsorbant pour purifier les ingrédients actifs du stévia et obtenir une concentration élevée de RA. [Traduit par la Rédaction] Mots-clés: réseau métallo-organique fonctionnalisé par un acide boronique (MOF-BA), séparation, stévioside, rébaudioside A., Introduction Steviol glycosides (SGs) extracted from Stevia rebaudiana Bertoni leaves are a high-quality natural sweetener and dietary supplement. (1,2) Owing to their high sweetness (250-450 times sweeter than sugar), zero [...]

Cell active inhibitors of glycoside processing enzymes are valuable research tools that help us understand the physiological roles of this diverse class of enzymes. endo-N-Acetylglucosaminidases have gained increased attention for their important roles in both mammals and human pathogens; however, metabolically stable cell active inhibitors of these enzymes are lacking. Here, we describe a divergent synthetic strategy involving elaboration of a thiazoline core scaffold. We illustrate the potential of this approach by using the copper catalysed azide-alkyne click (CuAAC) reaction, in combination with a suitable catalyst to avoid poisoning by the thiazoline moiety, to generate a targeted panel of candidate inhibitors of endo-N-acetylglucosaminidases and chitinases. Key words: enzyme inhibitor, glucosaminidase, substrate-assisted catalysis, thiazoline. Les inhibiteurs d'enzymes de transformation des glycosides actifs en milieu cellulaire constituent des outils de recherche precieux qui aident a comprendre les roles physiologiques de cette classe diversifiee d'enzymes. On a decouvert que les endo-N-acetylglucosaminidases jouaient un role important chez les pathogenes affectant tant les mammiferes que les humains. Cependant, on ne dispose pas d'inhibiteurs de ces enzymes qui soient stables et actifs en milieu cellulaire. Dans le present article, nous decrivons une strategie de synthese divergente faisant intervenir l'elaboration d'une structure centrale a base de thiazoline. Au moyen d'une reaction catalysee par le cuivre de type << clic >> entre un azoture et un alcyne dans laquelle nous avons employe un catalyseur compatible afin d'eviter qu'il soit empoisonne par le fragment thiazoline, nous illustrons le potentiel de cette approche pour generer une serie ciblee de composes susceptibles d'inhiber les endo-N-acetylglucosaminidases et les chitinases. [Traduit par la Redaction] Mots-cles: inhibiteur enzymatique, glucosaminidase, catalyse assistee par le substrat, thiazoline., Introduction endo-N-Acetylglucosaminidases, including chitinases and hyaluronidases, are responsible for hydrolyzing the glycosidic bonds of 2-acetamido-2-deoxy-[beta]-D-glucopyranose (GlcNAc) residues found within oligosaccharides and polysaccharides. (1) These enzymes, along with muramidases, which process [...]

ARTICLE INFO Keywords: Black cohosh Actaea racemosa Cimicifuga racemosa Stability Shelf life Analysis Clinical ABSTRACT Concurrent to a clinical trial of black cohosh for menopausal hot flashes, the long-term stability [...]

Polyyne glycosides are a class of natural products that have been found in terrestrial plants, fungi, and marine algae. Many display interesting and potentially useful biological activities, which in some cases has initiated synthetic efforts toward their formation. This review provides a comprehensive report of polyyne glycosides isolated from natural sources, as well as the synthesis of these molecules and their analogues. Key words: polyynes, polyacetylenes, carbohydrates, natural products. Les glycosides de polyyne correspondent a une classe de produits naturels qu'on retrouve dans les plantes terrestres, les champignons et les algues marines. Plusieurs presentent des activites biologiques interessantes et potentiellement utiles qui, dans certains cas, ont conduit a l'initiation d'efforts de synthese orientes vers leur formation. Cette revue fournit un rapport approfondi sur les glycosides de polyyne isoles de sources naturelles et sur les efforts de synthese de ces molecules et de leurs analogues. Mots-cles : polyynes, polyacetylenes, hydrates de carbone, produits naturels. [Traduit par la Redaction], Introduction Polyynes (1) have long been known to exist in natural sources, and thousands have been isolated in the past century from a wide range of terrestrial plant species, fungi, [...]

The synthesis of 2-azidoacetyl-2-deoxy-5-fluoro-[beta]-D-gluopyranosyl fluoride is described as an activity-based proteomics probe for profiling these exo-glycosidases. The general strategy involving 5-fluoro inactivators can be used for profiling proteomes and also identifying glycoside hydrolases of medical importance or having desirable properties for biotechnology.

A novel liquid chromatography tandem mass spectrometry method for quantification of buprenorphine, norbuprenorphine, and glucuronidated conjugates was developed and validated. Analytes were extracted from meconium using buffer, concentrated by solid-phase extraction and quantified within 13.5 min. In order to determine free and total concentrations, specimens were analyzed with and without enzyme hydrolysis. Calibration was achieved by linear regression with a 1/x weighting factor and deuterated internal standards. All analytes were linear from 20 to 2000 ng/g with a correlation of determination of >0.98. Accuracy was [greater than or equal to]85.7% with intra-assay and interassay imprecision [less than or equal to] 13.9 and 12.4%, respectively. There was no interference from 70 licit and illicit drugs and metabolites. Buffer extraction followed by SPE yielded recoveries of [greater than or equal to]85.0%. There was suppression of ionization by the polar matrix; however, this did not interfere with sensitivity or analyte quantification due to inclusion of deuterated internal standards. Analytes were stable on the autosampler, at room temperature, at 4[degrees]C, and when exposed to three freeze/thaw cycles. This sensitive and specific method can be used to monitor in utero buprenorphine exposure and to evaluate correlations, if any, between buprenorphine exposure and neonatal outcomes.

Studies have shown that S-benzoxazolyl (SBox) glycosides are stable toward major protecting group manipulations used in carbohydrate chemistry. Selective and chemoselective activations of the SBox moiety are shown to be feasible, which is demonstrated by preparing many oligosaccharide sequences.

A range of S-benzoxazolyl (SBox) glycosides are prepared. The mechanistic aspects of the SBox moiety activation for glycosylation through different pathways are examined in the presence of thiophilic, electrophilic, or metal-based promoters.

The characterization of active and non-active histidines demonstrates its role in probing the electrostatic interactions along the reaction pathway of a glycoside hydrolase. The results show that histidine play very significant structural and functional roles in the hydrolase because of its diverse ionization behaviors.

[alpha]-Deuterium kinetic isotope effects ([alpha]-DKIEs) are used for mechanistic studies on the [beta]-selective glycosidation of trimethylene oxide (TMO) from mannosyl iodides. The transition structure geometries for these reactions have shown that the KIEs are consistent with very loose [S.sub.N]2-like processes.

The characterization of amylomaltase from the hyperthermophilic bacterium Thermus thermophilus HB8 (Tt AMase), the roles of the putative catalytic residues and the identification of acceptor subsites +2 and +3 in the active site are reported. The results have shown that the main catalytic machinery is the same for glycoside hydrolase family 77 (GH77) and GH13, whereas the properties of acceptor subsite +2 has distinguished the two families.

The umu test method was used to evaluate mutagenic potential of 6 major kavalactones and different solvent fractions of kava roots, leaves, and stem peelings. The study results suggest that organic solvent extraction of kava leaves might yield potentially toxic compounds like flavonoids that damage DNA directly or indirectly and to ensure the potentially toxic components below tolerance levels in the kava products a reliable analytical method are required for product quality control.

Endolysins have been found to be capable of cleaving most bonds in peptidoglycan. Study is presented to show that the minimum peptide sequence necessary in a substrate for the phage B30 lysin is DL-gamma-Glu-Lys-D-Ala-Ala-Ala.

The access to piperidine homoazasugars (dideoxyiminoheptitols) from pyranoses through formal one-carbon chain elongation and exchange of the ring oxygen with the NH group is described. Cleavage of the thiazole residue attached to C2 of the piperidine ring reveals the formyl group, which is reduced to hydroxymethyl to give the target homoazasugar.

Molecular modeling studies were conducted comparing the active site regions of T4-Pdg and the Escherichia coli formamidopyrimidine DNA glycosylase (Fpg) to test whether comparable residues and mechanisms might be operative for other base excision repair (BER) glycosylase:AP lyases. Analyses revealed that His71 in Fpg, when mutated, is an essential residue for the biologically required turnover of the Fpg AP-lyase covalent enzyme-product species.

The attempted synthesis of the 2-acetamido and 2-amino derivatives of salacinol, a naturally occurring glycosidase inhibitor is described. Reaction of the protected acetamidothioarabinitol gave the corresponding sulfonium sulfate, which underwent ring opening to give an acyclic amido sulfate.

A different method is developed and partly optimized for the stereoselective synthesis of glycosyl amides based on the traceless Staudinger ligation of glycosyl azides with triaryl phosphines diphenylphosphanyl-phenyl esters. The funtionalized phosphine reagents employed in this reaction could be easily prepared on multigram scale.

The gene corresponding to the N-terminal glycoside hydrolase family 43 (GH43) module is expressed in Escherichia coli and the gene product is characterized. The results have shown that exo-beta-1,3-galactanases are one of the components of cellulosomes and that the enzymes are widely distributed in nature.

The structures of inactive mutants D144a and E78Q of the glycoside hydrolase family 8 (GH- 8) endo- beta-1,4-D-xylanase (pXyl) from the Antarctic bacterium Pseudoalteromonas haloplanktis TAH3a in complex with its substrate xylopentaose (at 1.95 Angstrom resolution) and product xylotriose (at 1.9 A resolution) is determined. Analysis of the crystal structures of the pXyl mutants D144A and E78Q in complex with substrate and product, indicates that substrate specificity in GH- 8 xylanases is determined by structural features at subsites +2, -1, and -2.

A novel approach to the synthesis of urea glycosides in aqueous media is explored. The method was successfully applied to establish an unknown route for the synthesis of urea-tethered neoglycoconjugates and pseudooligosaccharides in water.

Two mutants of human O-GlcNAcase, D174A and D175A are generated and structure-reactivity studies of the D174A mutant enzyme reveals severely impaired catalytic activity while the D175A mutant enzyme shows a significant decrease in catalytic efficiency with substrates bearing poor leaving groups. These results clearly identify Asp(super 174) as the residue that polarizes the 2-acetamido group for attack on the anomeric center and Asp(super 175) as the residue that functions as the general acid/base catalyst.

Comparative molecular dynamics simulations of n-octyl-beta-D-galactopyranoside (beta-C8Gal) and n-octyl-beta-D-glucopyranoside (beta-C8Glc) micelles in aqueous solution are performed to examine the influence of carbohydrate stereochemistry on glycolipid properties at the atomic level. The simulations have predicted the differences in hydrogen bonding for the two headgroup stereochemistrics, including a small difference in inter-headgroup interactions, which might contribute to the higher Tm and Tc values of beta-C8Gal surfactants relative to beta-C8Glc in lyotropic systems.

A stereoselective synthesis of C-glycoside analogue of is achieved starting from tetra-O-benzyl-D-galacropyranosyl lactone. Amino acid beta-D-galactosyl-(5R,2S)-hydroxylysine was incorporated in a flycopeptide from type II collagen known to be crucial for the response of autoimmune T cells obtained in models of rheumatoid arthritis.

The intrinsic conformer specific vibrational spectra of two subunits of the core pentasaccharide of N-linked glycans, the alpha(1,3) and alpha(1,6) dimannosides is recorded in the gas phase. These measurements and computational studies are used to enable their conformational assignment and identify characteristic vibrational signatures associated with particular conformational families, including those that do or do not display inter-ring hydrogen bonding across the glycosidic linkage.

The synthesis of two enantiomerically pure iminosugars, analogues of 1-L-deoxynojirimycin and 1-D-deoxymannojirimycin is achieved and their evaluation as glycosidase inhibitors is presented. Glycosidases are widely distributed in microorganisms, plants, and animals, and they selectively hydrolyze glycosidic bonds and play important roles in crucial biological pathways, including polysaccharide and glycoconjugate anabolism and catabolism, cellular recognition, and eukaryotic glycoprotein processing.

Monofunctional base excision repair enzymes (BER) are DNA glycosylases that hydrolyze N-glycoside bonds to create a common product from disparate types of DNA damage and remove the damaged nucleobase by glycosyl transfer. Direct transition state (TS) analysis of uracil DNA glycosylase and indirect TS analyses of related reactions, like the ricin-catalyzed reactions, help in a better understanding of BER enzymes.

A general procedure for the stereoselective synthesis of 2-deoxy-2-iodo-hexo- and -hepto-pyranosyl glycosides from furanoses is reported. This methodology provides a new avenue for accessing 2-deoxy-oligosaccharides.

Two xyloglucan-specific endo-beta-1,4-glucanases (xyloglucanases [XEGs]), XEG5 and XEG74, are isolated from the gram-positive bacterium Paenibacillus species strain KM21 and the genes encoding these XEGs are cloned and sequenced. The analysis using various oligosaccharide structures has shown that unique structures of xyloglucan oligosaccharides can be prepared with XEG74.

The enzyme beta-xylosidase from Trichoderma reesei, a member of glycosil hydrolase family 3 (GH3), is a glycoside hydrolase which acts at the glycosidic linkages of 1,4-Beta-xylooligosaccharides and that also exhibits alpha-L-arabinofuranosidase activity on 4-nitrophenyl Alpha-L-arabinofuranoside. Enzyme forms monomers in solution and derive that low-resolution molecular envelope of the Beta-xylosidase from small-angle X-ray scattering (SAXS) data using the ab ignition simulated annealing algorithm.

Glycosyl disulfides that are shown for the first time to be effective glycosyl donors are discussed. Glycosyl disulfide donors use in latent active reactivity tuning strategies due to their ability to easily alter the nature of the aglycon and the ability to differently activate donors that differ only in their aglycon simply through altering continues.

A constrained method on how the chosen mathematical constraints, which are derived from the normal modes of six-membered rings, enable the study of conformational transition among selected pyranose conformations in both static and dynamic calculations is presented. The results demonstrate that the method is able to stimulate accurate trajectories for the chair inversion of several pyranose conformation and to calculate free-energy barrier that are in excellent agreement with both established static calculations and experimental data.

(6(super A)R,6(super D)R)-6(super A),6(super D)-Di-C-cyano-beta-cyclodextrin and 6(super A),6(super D)-di-C-cyano-alpha-cyclodextrin are synthesized and shown to catalyze hydrolysis of aryl glycosides into glucose and phenol with a reaction following Michaelis-Menten kinetics. Cyclodextrin cyanohydrins are shown to be remarkably efficient artificial enzymes catalyzing close to 10(super4).

A number of methods for the total synthesis of bicyclic perhydrofuropyran nucleosides as N-analogues of the naturally occurring malayamycin A are described in a study. Formation of the N-nucleosides relied on the activation of thioglycosides, proceeding through sulfonium intermediates.

A quartz-crystal microbalance (QCM) technique is applied to analyze effects of site-directed mutagenesis of a glycosidase (isomalto-dextranase) on the hydrolysis mechanism of the substrate binding and the catalytic process. An estimate of the reaction mechanism is made in which Asp266 acts as only a general acid in the catalytic process, Asp198 acts as both nuclephile in the catalytic process and binding the substrate, and Asp313 acts as only the substrate binding.

An approach to the pyranopyran ring system that is found in many natural products, including thyrsiferol, is described. The route entails the assembly of an alpha, beta-unsaturated ketone from geraniol and dihydropyran from acetyl acetaldehyde dimethyl acetal and their titanium(III)-promoted coupling to afford a respectable 60% yield of keto alcohol.

1,2-cyclopropanated sugars are reacted with various alcohols, thiols and sodium azide to produce 2-C-branched O-, S-glycosides and glycosyl azides in good to excellent yields. The mechanism controlling the competitive 1,2-cyclopropanation and beta-elimination process is discussed.

A coupling of 2-O-arylmethylated D-glucose-derived thioglycosides with various alcohols in the presence of CF(sub 3)SO(sub 3)(super -)(S(super +)Me(sub 2)SMe (DMTST) as an activator is described. When the aryl group is the 9-anthracenylmethyl group, a highly stereoselective formation of the unusual C-glycosides in good yields via neighboring group participation of the 9-anthracenylmethyl group followed by coupling with a variety of alcohols is observed.

The first synthesis of (plusmn)-C-aryl-6-fluoro and -6,6-difluoro olivosides is described through the allylic mono- and difluorides produced by regioselective fluorination of hydroxyalkyl and oxoalkyl derivatives respectively. A preliminary study points out the efficiency of the straightforward sequence in C-alkyl series.

The role of the catalytic lysine (Lys 249) in breaking the glycosidic bond of 8-oxoguanine in the enzyme human 8-oxoguanine DNA glycosylase is examined. It has investigated several different reaction mechanisms to discover plausible ways where the lysine could assist in breaking the glycosidic bond.

Frondosides [A.sub.2]-1 (1), [A.sub.2]-2 (2), [A.sub.2]-3 (3), and [A.sub.2]-6 (4) are new monosulfated holostane pentaosides isolated from the sea cucumber Cucumaria frondosa. Their structures have been elucidated on the basis of spectral data (2D NMR and MS). Frondoside [A.sub.2]-2 (2) contains an [alpha],[beta]-unsaturated ketone fragment in the side chain of the aglycon, unique for triterpene glycosides of sea cucumbers. Key words: Cucumaria frondosa, sea cucumbers, frondosides, triterpene glycosides.

An efficient strategy for the generation of HS-like fragments [GlcA -beta-(1,4)-GlcNAc] and related dimerized (gemini) disaccharides via n-pentynyl glycoside formation is reported. When a convergent synthetic approach was utilized, construction of target molecules was achieved through a combination of chemoselective protection/deprotection protocols, imidate and n-pentenyl glycosylation, and functional group manipulations followed by ozonolysis and reductive amination.

The utilization of both intermediates as possible precursors to spirocyclic mimics of DNA building blocks was shown to generate appreciable levels of the Alpha-anomers. In select cases where Ch2Cl2 served as solvent, the proportion of the latter end-products was very predominant.

The reaction of alpha vinyl oxirane prepared through a new route to the D-gulal system, with O-nucleophiles and C-nucleophiles affords in a completely sterreoselective way, the corresponding 2-unsaturated alpha O-and C-glycosides having the same configuration as the starting epoxide.

The synthesis of thioglycoside derived UDP-sugar derivatives as potential substrate based inhibitors is reported. Four glycosylthiomethyl phosphonates are also prepared to mimic the naturally occurring glycosyl phosphates, which play a vital role in the carbohydrate metabolism.

An evaluation is made of whether the well-known deactivating effect of a 4,6-acetal protection group on glycosyl transfer is caused by torsional or an electronic effect from fixation of the 6-OH in the tg conformation. Kinetic results from acid-catalyzed glycoside hydrolysis of three methyl glycosides and spontaneous dinitrophenyl glycoside hydrolysis confirmed the existence of a disarming torsional effect.

A study shows that beta-glycosides of D-GlcNAc can be readily transformed into unsaturated aldehyde derivatives. It is found that these glycosides provide attachment of the CMP (cytidine monophosphate) residue to the generated hydroxy group.

The structure of the formed ortho esters determined by X-ray single cystallographic analysis and molecular modeling studies are presented. By comparing the structures of these ortho esters stability between two possible isomers caused by spiro ring systems in their molecules are also discussed.

The preparation of beta-glycosides by the reductive cleavage of spiro sugar ortho esters is based on preparation of various combinations of sugar lactones and beta-diol type sugars. The remarkable high beta-selectivity was observed at the anomeric centers of the resulting disaccharides.

The indolo[2,3-alpha]carbazole glycosides are potent antitimor antibiotics undergoing chinical trials for the treatment of a several types of cancer. AT2433-A1 is the most complex member of the family of compounds possesing a unique disaccharide with a sensitive aminodeoxysugar and an unsymmetric aglycon.

Molecular dynamics simulations of the disaccharide alpha-D-Manp-(1->3)-beta-D-Glep-OMe are performed in vacuo and water solution and hetronucelar scalar coupling constants are also measured across the glycosidic linkage. From MD simulations of parameters deducible from NMR experiments it can be concluded that the disaccharide can be described as having a single major conformation of limited flexibility.