Showing papers on "Pyranose published in 2015"

Scalable Synthesis of the Potent HIV Inhibitor BMS-986001 by Non-Enzymatic Dynamic Kinetic Asymmetric Transformation (DYKAT)†

Abstract: Described herein is the synthesis of BMS-986001 by employing two novel organocatalytic transformations: 1) a highly selective pyranose to furanose ring tautomerization to access an advanced intermediate, and 2) an unprecedented small-molecule-mediated dynamic kinetic resolution to access a variety of enantiopure pyranones, one of which served as a versatile building block for the multigram, stereoselective, and chromatography-free synthesis of BMS-986001. The synthesis required five chemical transformations and resulted in a 44 % overall yield.

Characterization of a Novel PQQ-Dependent Quinohemoprotein Pyranose Dehydrogenase from Coprinopsis cinerea Classified into Auxiliary Activities Family 12 in Carbohydrate-Active Enzymes

Abstract: The basidiomycete Coprinopsis cinerea contains a quinohemoprotein (CcPDH named as CcSDH in our previous paper), which is a new type of pyrroloquinoline-quinone (PQQ)-dependent pyranose dehydrogenase and is the first found among all eukaryotes. This enzyme has a three-domain structure consisting of an N-terminal heme b containing a cytochrome domain that is homologous to the cytochrome domain of cellobiose dehydrogenase (CDH; EC 1.1.99.18) from the wood-rotting basidiomycete Phanerochaete chrysosporium, a C-terminal family 1-type carbohydrate-binding module, and a novel central catalytic domain containing PQQ as a cofactor. Here, we describe the biochemical and electrochemical characterization of recombinant CcPDH. UV-vis and resonance Raman spectroscopic studies clearly reveal characteristics of a 6-coordinated low-spin heme b in both the ferric and ferrous states, as well as intramolecular electron transfer from the PQQ to heme b. Moreover, the formal potential of the heme was evaluated to be 130 mV vs. NHE by cyclic voltammetry. These results indicate that the cytochrome domain of CcPDH possesses similar biophysical properties to that in CDH. A comparison of the conformations of monosaccharides as substrates and the associated catalytic efficiency (kcat/Km) of CcPDH indicates that the enzyme prefers monosaccharides with equatorial C-2, C-3 hydroxyl groups and an axial C-4 hydroxyl group in the 1C4 chair conformation. Furthermore, a binding study shows a high binding affinity of CcPDH for cellulose, suggesting that CcPDH function is related to the enzymatic degradation of plant cell wall.

Purification and Structural Identification of Polysaccharides from Bamboo Shoots (Dendrocalamus latiflorus)

Abstract: Three kinds of polysaccharides, namely, BSP1A, BSP2A, and BSP3B, were isolated from raw bamboo shoot (Dendrocalamus latiflorus) after purification and classification by DEAE cellulose-52 (ion-exchange chromatography) and Sephadex G-50. The molecular weights of BSP1A, BSP2A, and BSP3B were 10.2, 17.0 and 20.0 kDa, respectively, which were measured through GPC (gel performance chromtatography) methods. BSP1A contained arabinose, glucose, and galactose in a molar ratio of 1.0:40.6:8.7. BSP2A and BSP3B contained arabinose, xylose, glucose, and galactose in molar ratios of 6.6:1.0:5.2:10.4 and 8.5:1.0:5.1:11.1, respectively. The existence of the O-glycopeptide bond in BSP1A, BSP2A, and BSP3B was demonstrated by β-elimination reaction. FTIR spectra of the three polysaccharides showed that both BSP2A and BSP3B contained β-d-pyranose sugar rings. However, BSP1A exhibited both β-d-pyranose and α-d-pyranose sugar rings. Congo red test indicated that BSP1A and BSP2A displayed triple helix structures, but BSP3B did not. NMR spectroscopy revealed that BSP1A may exhibit a β-1,6-Glucan pyran type as the main link, and few 1,6-glycosidic galactose pyranose and arabinose bonds were connected; BSP2A mainly demonstrated →5)β-Ara(1→and→3)β-Gal(1→connection. Furthermore, BSP3B mainly presented →3)β-Glu(1→and→3)β-Gal(1→connection and may also contain few other glycosidic bonds.

Engineering of pyranose dehydrogenase for application to enzymatic anodes in biofuel cells

Abstract: In the search for improved glucose oxidising enzymes for biofuel cells, a number of Agaricus meleagris (Am) pyranose dehydrogenase mutants (mPDHs) exhibiting different degrees of glycosylation were produced using site-directed mutagenesis and electrochemically characterised. The response of electrodes modified with different mPDHs is compared in a mediated electron transfer mode, where the electrodes are modified with each of the mutants covalently attached to redox polymers based on polyvinylimidazole-bound osmium complexes using a cross-linking agent. Coating of each of the enzymes onto the graphite electrode surface is also used to screen for their capacity for direct electron transfer. The double mutant PDH exhibits the highest response to glucose at physiological pH in both direct and mediated electron transfer modes, producing a Jmax of ≈800 μA cm(-2) at room temperature and when "wired" to the Os-polymer having the highest formal potential. From the results obtained the double mPDH is proposed as the most suitable candidate for application to bioanode fabrication.

Opening of the 1,6-anhydro bridge with selective reduction of the acetal moiety in levoglucosenone and its derivatives

Abstract: Treatment of levoglucosenone and some its derivatives with chloro(trimethyl)silane and sodium iodide in acetonitrile leads to opening of the 1,6-anhydro bridge and simultaneous reduction of the pyranose ring to pyran.

High-temperature molecular dynamics simulation of cellobiose and maltose

Abstract: Thermochemical conversion of lignocellulosic biomass to renewable fuels and chemicals occurs through high temperature decomposition of the main structural components in plants, including cellulose, hemicellulose, and lignin. Cellulose and hemicellulose comprise mostly carbohydrates. Two disaccharides, maltose and cellobiose, are used as model compounds to explore differences in thermal stability due to the orientation of the glycosidic bond. First principles molecular dynamics and density functional theory have been used to probe the decomposition of these disaccharides during pyrolysis at 700 K. The results suggest that maltose, the α-disaccharide, is less thermally stable. Dynamic bond length analysis for maltose indicates that several CC bonds and the CO bonds on the pyranose ring demonstrate signs of weakening, whereas no such scissile bonds were identified for cellobiose. The higher stability of the cellobiose is believed to originate from the persistence of low-energy hydroxymethyl conformers throughout the simulation which enable strong inter-ring hydrogen bonding. Thermogravimetric and mass spectroscopic experiments corroborate the enhanced thermal stability of cellobiose, wherein the onset of decomposition was observed at higher temperatures for cellobiose than for maltose. © 2015 American Institute of Chemical Engineers AIChE J, 61: 2562–2570, 2015

Reaction of pyranose dehydrogenase from Agaricus meleagris with its carbohydrate substrates.

Abstract: Monomeric Agaricus meleagris pyranose dehydrogenase (AmPDH) belongs to the glucose-methanol-choline family of oxidoreductases. An FAD cofactor is covalently tethered to His103 of the enzyme. AmPDH can double oxidize various mono- and oligosaccharides at different positions (C1 to C4). To study the structure/function relationship of selected active-site residues of AmPDH pertaining to substrate (carbohydrate) turnover in more detail, several active-site variants were generated, heterologously expressed in Pichia pastoris, and characterized by biochemical, biophysical and computational means. The crystal structure of AmPDH shows two active-site histidines, both of which could take on the role as the catalytic base in the reductive half-reaction. Steady-state kinetics revealed that His512 is the only catalytic base because H512A showed a reduction in (kcat /KM )glucose by a factor of 10(5) , whereas this catalytic efficiency was reduced by two or three orders of magnitude for His556 variants (H556A, H556N). This was further corroborated by transient-state kinetics, where a comparable decrease in the reductive rate constant was observed for H556A, whereas the rate constant for the oxidative half-reaction (using benzoquinone as substrate) was increased for H556A compared to recombinant wild-type AmPDH. Steady-state kinetics furthermore indicated that Gln392, Tyr510, Val511 and His556 are important for the catalytic efficiency of PDH. Molecular dynamics (MD) simulations and free energy calculations were used to predict d-glucose oxidation sites, which were validated by GC-MS measurements. These simulations also suggest that van der Waals interactions are the main driving force for substrate recognition and binding.

Anionic ring-opening polymerization of five-membered cyclic carbonates derived from aldohexopyranosides

Abstract: To investigate the relationship between the steric structures and polymerizability of five-membered cyclic carbonates, the anionic ring-opening polymerizations of methyl 4,6-O-benzylidene-2,3-O-carbonyl-α-d-galacto- and mannopyranosides (MBCGa and MBGM, respectively), were examined and compared to the results of the already reported glucopyranoside analog (MBCG). The polymerization of MBCGa proceeded without the elimination of CO2 as in the case of MBCG, while MBCM was not polymerized. To estimate the thermodynamic stability of the carbonate rings of these cyclic carbonates, the model reactions using the corresponding hydroxycarbonates were carried out. The ring-closing reactions of the mannopyranoside-based hydroxycarbonate proceeded to produce cyclic carbonate, while the others did not give cyclic carbonates. This should indicate that the carbonate rings of MBCG and MBCGa were less stable than that of MBCM. The single-crystal X-ray structural analysis indicated that the carbonate rings of MBCG and MBCGa have higher angle strains than that of MBCM. This should suggest that the ring strain of the five-membered cyclic carbonate increases by trans-fusing to the pyranose ring.

Prebiotic glycosylation of uracil with electron-donating substituents.

Abstract: Following the suggestion that nucleoside analogues having their nucleobases joined to ribose via a carbon-carbon bond might easily arise prebiotically, the glycosylation of uracil carrying electron-donating substituents (Me, OH, OCH3, NH2) at its 5 or 6 positions was investigated. Of these, only 6-aminouracil gave glycosylated products in greater than 50% yield under simulated prebiotic conditions. The reaction provided four products, three of which were purified by preparative HPLC. The structure of the isolated compounds was determined by high-resolution mass spectrometry and NMR spectroscopy. The glycosylation products were, as expected, C-nucleosides, with the sugar having either a pyranose or a furanose structure, with the ratio depending on the precise conditions, implying reversible addition. Interestingly, the 6-aminouracil riboside displays two hydrogen bonding patterns, the "acceptor-donor-acceptor" pattern of uridine itself and (upon 180° rotation) the "acceptor-donor-donor" hydrogen bonding pattern. The second, in an artificially expanded genetic information system, is trivially called "V" and pairs with a purine analogue that presents the complementary "donor-acceptor-acceptor" hydrogen bonding pattern, trivially called "J."

Tandem mass spectrometric characterization of the conversion of xylose to furfural

Abstract: Thermal decomposition of xylose into furfural under acidic conditions has been studied using tandem mass spectrometry. Two different Bronsted acids, maleic and sulfuric acids, were used to demonstrate that varying the Bronsted acid does not affect the mechanism of the reaction. Two selectively labeled xylose molecules, 1-13C and 5-13C-xyloses, were examined to determine which carbon atom is converted to the aldehyde carbon in furfural. This can be done by using tandem mass spectrometry since collision-activated dissociation (CAD) of protonated unlabeled furfural results in the loss of CO from the aldehyde moiety. The loss of a neutral molecule with MW of 29 Da (13CO) was observed for protonated furfural derived from 1-13C-labeled xylose while the loss of a neutral molecule with MW of 28 Da (CO) was observed for protonated furfural derived from 5-13C labeled xylose. These results support the hypothesis that the mechanism of formation of furfural under mildly hot acidic conditions involves an intramolecular rearrangement of protonated xylose into the pyranose form rather than into an open-chain form.

Unexpected furanose/pyranose equilibration of N-glycosyl sulfonamides, sulfamides and sulfamates

Abstract: De-protected arabino N-glycosyl sulfamides, sulfonamides and sulfamates were found to mutarotate and convert from the furanose to the thermodynamically more stable pyranose form in aqueous solution. The presence of a strongly electron withdrawing group in the alkyl chain stopped mutarotation and furanose/pyranose equilibration, allowing the isolation of the first unprotected furanose N-glycosyl sulfonamide.

Comparative Antibacterial Activities of Some Monosaccharide and Disaccharide Benzoates

Abstract: For comparative antibacterial studies a number of furanose ( 3 , 5 ), pyranose ( 7 , 9 , 11 , 13 ), and disaccharide benzoates ( 14 , 15 ) were prepared by direct benzoylation method. Synthesized benzoates ( 3 , 5 , 7 , 9 , 11 , 13 - 15 ) along with some starting materials were screened for in vitro antibacterial activity against ten human pathogenic bacteria viz. Bacillus subtilis, Bacillus cereus, Bacillus megaterium, Staphylococcus aureus, Escherichia coli, INABA ET (Vibrio), Pseudomonas species, Salmonella paratyphi, Salmonella typhi, and Shigella dysenteriae. The study revealed that the pyranose benzoate derivatives ( 7 , 9 , 11 , 13 ) were more prone towards antibacterial functionality than that of the furanose benzoate ( 3 , 5 ) and disaccharide benzoates ( 14, 15 ). DOI: http://dx.doi.org/10.17807/orbital.v7i2.699

Stability of conformationally locked free fructose: theoretical and computational insights

Abstract: Despite many experimental and theoretical investigations, a quantitative explanation of the factors governing the stability of sugars is rather scarcely attempted in the literature. A quantitative understanding of such factors is important for correlating the stability of these molecules with their function. Recent experimental–theoretical studies report the global minimum structure of fructose and provide qualitative information about the predominant factors that determine the overall stability. In the present work, we quantitatively show that the relative stability of different conformers of fructose in the gas phase, albeit somewhat approximately, can be obtained in terms of the collective effect of (i) the sum of the energies of all the hydrogen bonds in a given conformer, (ii) the strain energy of a bare fructose ring, and (iii) the sum of anomeric stabilization (endo + exo) energies. The combined effect of these three factors is indeed useful for explaining the conformational landscape of fructose. The calculated relative stability of fructose is in good agreement with the one obtained from the relative energies of these sugar molecules. The large energetic gap between pyranose and furanose conformers is also well-explained. It is concluded that the small ring strain, the sufficiently large sum of the energies of the intramolecular hydrogen bonds and the higher stabilization due to anomeric interactions in β-fructo-pyranose make it a conformationally locked predominant structure in the gas phase.

Synthesis of 1,2,3-triazole-linked glycohybrids in the gluco-, gulo-, and allopyranose series

Abstract: Ketone derived from diacetone-α-D-glucose is a suitable starting material for the synthesis of 3-C-linked glycohybrids containing 1,2,3-triazole moiety as an intersugar linkage. The pyranose tautomers of 3-deoxy-3-(1,2,3-1H-triazol-1-yl)glucose, 3-C-[(1,2,3-1Htriazol-1-yl)methyl]allose and 3-C-[(1,2,3-1H-triazol-1-yl)methyl]gulose moieties are released upon the acidic hydrolysis of the corresponding O-isopropylidene-protected furanosyl-type synthetic intermediates. Some of the title compounds show a rare property of activating β-galactosidase from Escherichia coli.

Pyranose glycals in the generation of skeletal diversity

Abstract: The presence of an unsaturation in a pyranose derivative provides a powerful handle for the creation of new compounds displaying a variety of molecular skeletons. This contribution focuses on investigations related to the use of pyranose glycals in the creation of skeletally-diverse derivatives that have appeared in the literature during the last eight years.

Polarizing plate and liquid crystal display device

Abstract: A polarizing plate (3) in which the total thickness of a first protective film (11), a polarizing film (12), and a second protective film (13) is 90 [mu]m or less The moisture permeability of the first protective film (11) is equal to or less than 400 g/m224 hr The second protective film (13) contains a cellulose ester and a retardation-lowering agent The retardation-lowering agent contains a sugar ester obtained by esterifying, using an aliphatic acyl group, all or some of the OH groups in a compound (A) having a furanose structure or a pyranose structure or a compound (B) in which two to twelve furanose structures and/or pyranose structures are bonded together The second protective film (13) has an Ro of 0 to 10 nm and an Rt of -10 to +10 nm

Synthesis of 1,2,3-Triazole-Linked Glycohybrids in the Gluco-, Gulo-, and Allopyranose Series

Abstract: Ketone derived from diacetone-α-D-glucose is a suitable starting material for the synthesis of 3-C-linked glycohybrids containing 1,2,3-triazole moiety as an intersugar linkage. The pyranose tautomers of 3-deoxy-3-(1,2,3-1H-triazol-1-yl)glucose, 3-C-[(1,2,3-1Htriazol-1-yl)methyl]allose and 3-C-[(1,2,3-1H-triazol-1-yl)methyl]gulose moieties are released upon the acidic hydrolysis of the corresponding O-isopropylidene-protected furanosyl-type synthetic intermediates. Some of the title compounds show a rare property of activating β-galactosidase from Escherichia coli.

Reactivity of damaged pyrimidines: formation of a Schiff base intermediate at the glycosidic bond of saturated dihydrouridine.

Abstract: DNA glycosylases catalyze the first step of the base excision repair (BER) pathway. The chemistry used by these enzymes for deglycosylation has been largely considered as the chemistry of the oxocarbenium ion, e.g., direct rupture of the C1′–N1 bond resulting in an oxocarbenium ion intermediate. Here we present mechanistic studies revealing the 2′-deoxyribose isomerization and subsequent deglycosylation processes in two pyrimidine lesions: 5,6-dihydro-2′-deoxyuridine (dHdU) and 5,6-dihydrothymidine (dHT), formed via ionizing radiation damage to 2′-deoxycytidine and thymidine, respectively, under anoxic conditions. Acid or heat treatment of these two lesions leads to the production of two pairs of C1′ epimers containing a pyranose and a furanose, respectively, indicating that both lesions favor the rupture of the C1′–O4′ bond, resulting in a Schiff base intermediate at the N-glycosidic bond. Such a Schiff base intermediate was trapped and characterized by either Pd-catalyzed hydrogenation or thiol-mediated...

One-pot synthesis of bicyclic sugar oxazolidinone from D-glucosamine

Abstract: Herein we report a one-pot and efficient method for the synthesis of a 1,2-cis fused furanoside bicyclic oxazolidinone derivative of D-glucosamine via pyranose to furanose conversion and concomitant cyclization involving the N-Troc group. The D-glucosamine oxazolidinone derivative was efficiently transformed into oxazolidinones of D-xylosamine, D-allosamine and D-ribosamine.

Polysaccharide-based materials

Abstract: There is provided a plastic or gel material comprising a mixture of: (a) a compound of formula (I) or a mixture of two or more compounds of formula (I), (M a+ )c(X b- )d or a hydrate thereof, wherein c and d can be 1, 2 or 3, M a+ is a Group I or II metal cation, X b- is a monovalent, bivalent or trivalent anion; (b) one or more uncharged organic compounds, each of which compounds comprises at least one oxygen atom and at least one hydrogen atom that is capable of forming a hydrogen bond with X b- ; and (c) one or more polysaccharides, wherein each polysaccharide is a polymer of pyranose monomers, at least 30% of which monomers are in the α-anomeric conformation. There is also provided articles formed from such materials, uses of such materials and processes for forming such materials.

Aldehydic Nature and Conformation of 3,6-Anhydro-L-galactose Monomer

Abstract: We investigated the aldehydic nature and conformation of 3,6-anhydro-L-galactose (L-AnG) by using enzymes that bind L-AnG in a reactive conformation. We found that L-AnG, but not L-galactose, can be oxidized by E. coli L-lactaldehyde dehydrogenase (Ec_LADH); this observation suggests that L-AnG is an aldehyde belonging to the a-hydroxyaldehyde family. Because the native enzyme that catalyzes oxidation of L-AnG to its carboxylate is LAnG dehydrogenase (L-AnGDH), we compared the crystal structure and amino-acid sequences of Ec_LADH with those of L-AnGDHs. This analysis revealed that the two oxygen atoms in the a-hydroxyaldehyde moiety of L-AnG are essential for the reactions of Ec_LADH and LAnGDHs. A chemical database search indicated that two configurations of L-AnG are possible: a trans arrangement in which C-2 and C-5 hydroxyl groups are on the opposite side and a cis arrangement in which these groups are on the same side. Manual docking of the two forms of L-AnG into the active site of Pseudoalteromonas atlantica LAnGDH (Pa_L-AnGDH) revealed that only the trans LAnG configuration can be fitted into the active site of Pa_L-AnGDH. The identification of trans L-AnG suggests the existence of three L-AnG conformations: bicyclic pyranose, opened pyranose, and open-chain aldehyde. The conformation of L-AnG monomer (open-chain aldehyde) differs from that in agarose (bicyclic pyranose) or agarobiose (opened pyranose) because a five-membered anhydro ring is free to move and can find its most stable conformation. This study validates the assumption of trans-type open-chain aldehyde conformation of L-AnG that was applied in our previous studies.

Bioelectrochemical Behavior of the Composite PVP-Os/chitosan as a Mediator with Different Types of Enzymes at Graphite Electrode

Abstract: Chitosan was cross-linked to an osmium redox polymer, poly(4-vinylpyridine) osmium bipyridyl [PVP-Os-(bpy)2-Cl], to form PVP-Os-(bpy)2-Cl/chitosan composite known to make a porous and hydrophilic film with an enzyme. In this work we demonstrate such a composite is a useful trestle, for hosting various sugars oxidizing enzymes to construct biosensors. Glucose sensing ability has been proven with the following glucose oxidizing redox enzymes; Aspergillus niger glucose oxidase (AnGOX), Myriococcum thermophilum cellobiose dehydrogenase, (MtCDH), glycosylated Agaricus meleagris pyranose dehydrogenase (gAmPDH), fragmented deglycosylated Agaricus meleagris pyranose dehydrogenase (fdgAmPDH), and Aspergillus sp. glucose dehydrogenase (AspGDH), as well as recombinant Glomerella cingulata glucose dehydrogenase (rGcGDH).

Metal-ion Interactions with Sugars: Crystal Structure of Bis(4-dehydro-L-arabinose) Calcium Methanol Bishydrate

Abstract: The crystal structure of the metal-organic frame Ca(C5H9O5)2·CH3OH·2H2O (1) has been synthesized and characterized. Complex 1 belongs to a tetragonal P43212 space group. In complex 1, the sugar moiety shows a beta-L configuration of pyranose form. The calcium(II) is eight-coordinated, binding to four such sugar moieties, via O(1), O(2) of two molecules and O(3), O(4) of the other two, with the 4-hydroxy group being deprotonated. The water and methanol molecules are not coordinated to the calcium ion.

Cobalt(III) Complexes of D‐Galactosylamine

Abstract: The β-pyranose isomer of D-galactosylamine (1) formed complexes with three different cobalt(III) fragments. Crystals containing the dication [Co(tren)(β-D-Galp1N2H–1-κ2N1,O2)]2+ (3) showed coordination through the anomeric amino group (N1) and the deprotonated hydroxy group (O2) of the 4C1 β-pyranose form, which is also the major isomer of free galactosylamine. The cationic complexes [Co(fac-dien)(β-D-Galp1N2H–1-κ2N1,O2)]2+ (4) and [Co(phen)2(β-D-Galp1N2H–1-κ2N1,O2)]2+ (5) were analysed by NMR spectroscopy and showed the same coordination mode as 3. In terms of available ligand isomers it was shown that 1 exhibits an anomeric equilibrium in solution of both pyranose and both furanose forms as is typical for the parent glycose, galactose.