Showing papers on "Pyranose published in 2018"
TL;DR: By monitoring fluctuations in ionic current, it is shown that an engineered α-hemolysin nanopore modified with a boronic acid reacts reversibly with d-glucose as the pyranose isomer and d-fructose as either the furanose (β-d-fructofuranose) or the p Pyranose or the fructopyranosed isomer.
Abstract: Monosaccharides, such as d-glucose and d-fructose, exist in aqueous solution as an equilibrium mixture of cyclic isomers and can be detected with boronic acids by the reversible formation of boronate esters. The engineering of accurate, discriminating and continuous monitoring devices relies on knowledge of which cyclic isomer of a sugar binds to a boronic acid receptor. Herein, by monitoring fluctuations in ionic current, we show that an engineered α-hemolysin (αHL) nanopore modified with a boronic acid reacts reversibly with d-glucose as the pyranose isomer (α-d-glucopyranose) and d-fructose as either the furanose (β-d-fructofuranose) or the pyranose (β-d-fructopyranose). Both of these binding modes contradict current binding models. With this knowledge, we distinguished the individual sugars in a mixture of d-maltose, d-glucose, and d-fructose.
66 citations
TL;DR: The biological profiles indicate that the hydroxymethyl branch is crucial to neither potency nor selectivity, with O‐alkylation demonstrated to produce exquisite selectivity extending beyond glycosidase inhibition, to immunosuppressant and antibacterial activities.
Abstract: 3,4,5-Trihydroxypiperidines belong to the family of 1,5-dideoxy-1,5-iminosugar natural products and are structural analogues of pentose monosaccharides in the pyranose form. The biological activities of these apparently structurally simple molecules and their N- and O-alkylated and -arylated derivatives are no less remarkable than their C-6 hydroxymethyl counterparts of the hexoses (such as 1-deoxynojirimycin, DNJ). Their biological profiles indicate that the hydroxymethyl branch is crucial to neither potency nor selectivity, with O-alkylation demonstrated to produce exquisite selectivity extending beyond glycosidase inhibition, to immunosuppressant and antibacterial activities.
26 citations
TL;DR: Investigating the tandem mass spectrometry of regiospecifically labeled, deprotonated sucrose analytes utilizes density functional theory calculations to model the pertinent gas-phase fragmentation chemistry of the prevalent glycosidic bond cleavages and compares these predictions to infrared spectroscopy experiments on the resulting B1 and C1 product anions.
16 citations
TL;DR: A pyranose ring contraction of ethyl 1-thio-β-d-galactopyranosides has been discovered that proceeds with retention of aglycon under mildly acidic conditions (aq TFA in CH2Cl2).
15 citations
TL;DR: The results of simulations relying on the new set of parameters indicate that the conformation of glycosidic linkage is nearly unaffected by the chemical state of the carboxyl group, in contrary to the ring conformational equilibria.
Abstract: An extension of the GROMOS 56a6CARBO/CARBO_R force field for hexopyranose-based carbohydrates is presented. The additional parameters describe the conformational properties of uronate residues. The three distinct chemical states of the carboxyl group are considered: deprotonated (negatively charged), protonated (neutral), and esterified (neutral). The parametrization procedure was based on quantum-chemical calculations, and the resulting parameters were tested in the context of (i) flexibility of the pyranose rings under different pH conditions, (ii) conformation of the glycosidic linkage of the (1 → 4)-type for uronates with different chemical states of carboxyl moieties, (iii) conformation of the exocyclic (i.e., carboxylate and lactol) moieties, and (iv) structure of the Ca2+-linked chain–chain complexes of uronates. The presently proposed parameters in combination with the 56a6CARBO/CARBO_R set can be used to describe the naturally occurring polyuronates, composed either of homogeneous (e.g., glucuron...
15 citations
TL;DR: The simulation results showed that the cellulose inclusion complexes exhibited anisotropic properties, and the spatial structure of inclusion complexes, the hydrogen-bonding interaction between cellulose and solvent molecules, the diffusive property of solvent molecules and the distribution of water-water angles in celluloseclusion complexes were discussed in details.
14 citations
TL;DR: A conformational analysis of levoglucosan under isolation conditions, by means of microwave spectroscopy coupled with ultrafast laser vaporization in supersonic expansions, finds an inversion in the chair conformation of the pyranose ring forces the OH groups to adopt axial positions and completely changes the pattern of intramolecular H-bonds.
Abstract: Levoglucosan is one of the main products of the thermal degradation of glucose and cellulose and is commonly used as a tracer for biomass burning. Herein we report a conformational analysis of levoglucosan under isolation conditions, by means of microwave spectroscopy coupled with ultrafast laser vaporization in supersonic expansions. We observed three different conformations of levoglucosan in the gas phase. They all share a common heavy atom rigid bicyclic structure. The difference between the three of them lies in the network of intramolecular hydrogen bonds that arises from the OH groups at positions 2, 3 and 4. The different combinations of H-bonds give richness to the conformational landscape of levoglucosan. The gas phase conformers obtained in this work are compared to the crystal structure of levoglucosan previously reported. Although the heavy atom frame remains unchanged, there are significant differences in the positions of the H-atoms. In addition, the levoglucosan structure can be compared to the related glucose, for which gas phase conformational studies exist in the literature. In this case, in going from glucose to levoglucosan, there is an inversion in the chair conformation of the pyranose ring. This forces the OH groups to adopt axial positions (instead of the more favorable equatorial positions in glucose) and completely changes the pattern of intramolecular H-bonds.
12 citations
TL;DR: The results of the molecular dynamics-based conformational analysis concerning a series of pyranoses, namely: d-aldopentoses, d-ketohexoses as well as deoxy- and dideoxy- derivatives of aldo hexoses are described and the ring-inversion properties studied in the context of both the full chair-chair inversion and the chair-boat/skew-boat rearrangement are studied.
11 citations
TL;DR: In this article, a 1,2- cis -(α)-selective glycosylation has been developed, where an ortho -xylylene group bridged between 3-O and 6-O of d -glucosyl fluoride, which straddles the β-face of the pyranose ring, hinders the approach of gly cosyl acceptors from that face.
Abstract: A 1,2- cis -(α)-selective glycosylation has been developed. An ortho -xylylene group bridged between 3-O and 6-O of d -glucosyl fluoride, which straddles the β-face of the pyranose ring, hinders the approach of glycosyl acceptors from that face. The determination of the three-dimensional structure of the bridged glucosyl fluoride, the optimization process of the reaction conditions oriented toward kinetic control to realize the high α-selectivity, and the scope of the reaction are described.
11 citations
TL;DR: Anomer preferences for galacturonic acid and its derivatives were more sensitive to solvent polarity compared to other pyranoses, and this may be linked to the electrostatic potential and reduced stabilization of the equatorial anomeric OH group due to reduced hydrogen bonding.
Abstract: Equilibrium anomeric ratios are reported for pyranoses (hemiacetals) of glucuronic and galacturonic acid and their derivatives. These are compared to related gluco- and galactopyranoses and to deoxyfluorogluco- and deoxyfluorogalactopyranoses. An association between axial anomer stability and the sum of 1H NMR downfield chemical shifts for protons H-3 and H-5 was observed in D2O with gluco- and galactopyranoses as reference compounds. When compared to 2-hydroxytetrahydropyran in water, introduction of three OAc substituents and one carboxylic acid substituent leads to an increase in stability of the axial anomer by 0.89–1.05 kcal/mol. This is interpreted as the electron-withdrawing substituents causing a reduction in the steric (gauche) interaction and an increase in favourable Coulombic interaction between CH groups of the pyranose and the anomeric group through substituent deshielding effects. Anomer preferences for galacturonic acid and its derivatives were more sensitive to solvent polarity compared t...
9 citations
TL;DR: This work examines possible transitions and/or inversions induced by external forces in the pyranose ring in the chair conformation with two axial glycosidic bonds and concludes that interpretation of AFM force-extension curves is not necessarily straightforward.
TL;DR: The structure of condensation products of D-lactose and D-maltose with sulfanylacetic, 3-sulfanylpropanoic, and 2-Sulfanylbenzoic acid hydrazides has been studied 1H and 13C NMR spectroscopy as mentioned in this paper.
Abstract: The structure of the condensation products of D-lactose and D-maltose with sulfanylacetic, 3-sulfanylpropanoic, and 2-sulfanylbenzoic acid hydrazides has been studied 1H and 13C NMR spectroscopy. The condensation products obtained from the disaccharides and sulfanylacetohydrazide and 3-sulfanylpropanehydrazide have pyranose structure in the crystalline state, whereas those derived from 2-sulfanylbenzohydrazide have cyclic 1,3,4-benzothiadiazepine structure in crystal. All condensation products in solutions in most solvents (D2O, DMF-d7, DMSO-d6) exist as equilibrium mixtures of linear and cyclic pyranose and 1,3,4-benzothiadiazepine tautomers.
TL;DR: In this paper, suitably protected carbohydrates were joined together using 1,5 disubstituted 1,2,3-triazolylmethylene (1,5-DTM) linkers.
24 Dec 2018
TL;DR: N-Acetylgalactosamine (GalNAc) α-O-linked to l-threonine (Thr) (Tn antigen) and several mimics of this Tn antigen have been synthesized to explore the impact of the underlying amino acid in the presentation mode of the carbohydrate moiety.
Abstract: N-Acetylgalactosamine (GalNAc) α-O-linked to l-threonine (Thr) (Tn antigen) and several mimics of this Tn antigen have been synthesized to explore the impact of the underlying amino acid in the presentation mode of the carbohydrate moiety. The structural changes introduced in the Tn antigen mimics involve the replacement of the natural underlying Thr by non-natural amino acids while maintaining the α-O-glycosidic linkage of GalNAc or the substitution of this bond by α-C-glycosidic linkages. We also synthesized two bicyclic, conformationally restricted Tn antigen mimics. All of these compounds were subjected to a thorough conformational analysis in solution using NMR data, quantum mechanical (QM) calculations, and molecular dynamics simulations. Interestingly, in C-glycosides, the 1C4 chair conformation of the pyranose ring was predicted to be stable by QM calculations and experimentally supported by nuclear Overhauser effect cross-peaks and coupling constants observed in the NMR experiments.
TL;DR: In this paper, a 13C NMR and a single crystal X-ray diffraction study of 1-deoxy-1-(N-methylphenylamino)-d -sorbose (1) and 1deoxy -1-(n-methyl phenylaminoyl-d -psicose (2) was performed, and the Hirshfeld surface analysis revealed a significant contribution of non- or weakly polar interactions to the packing forces for both molecules.
TL;DR: In this paper, the reaction of 2S, 3S, 4R)-2,3,4,7-tetrahydroxy-6-oxoheptanals with lower alcohols produced protected 3-deoxy-d -arabino-2-heptulosonates.
Patent•
14 Dec 2018
TL;DR: In this article, a total synthesis method and application of pyranose pyrrolidine ketal alkaloid was described. But the method was not applied to the application of anti-aging drugs and cosmetics.
Abstract: The invention belongs to the technical field of chemical synthesis, and provides a total synthesis method and the application of pyranose pyrrolidine ketal alkaloid. According to the total synthesis method and the application, D-glucose is taken as a raw material to undergo reaction with dibenzylamine so as to generate fructose dibenzylamine, and isopropyl protection and Pd/C dehydrogenation reduction are carried out to obtain amino fructose. Maillard condensation reaction is carried out on dihydropyranone and the amino fructose, spiro reaction is completed under an acidic condition to obtaina pair of cyclization products which are diastereoisomers of each other, and the isopropyl protection group is directly removed under the acidic condition to obtain a 3-hydroxy analogue of the pyranose pyrrolidine ketal alkaloid. Barton-McCombie reaction is carried out on the cyclization products to remove the 3-hydroxy, and the isopropyl protection group is removed under the acidic condition to obtain the pyranose pyrrolidine ketal alkaloid. The pyranose pyrrolidine ketal alkaloid is used in anti-aging and anti-oxidation drugs and cosmetics.
Journal Article•
TL;DR: In this paper, an extension of the GROMOS 56a6CARBO/CARBO_R force field for hexopyranose-based carbohydrates is presented, where three distinct chemical states of the carboxyl group are considered: deprotonated, protonated and esterified.
Abstract: An extension of the GROMOS 56a6CARBO/CARBO_R force field for hexopyranose-based carbohydrates is presented. The additional parameters describe the conformational properties of uronate residues. The three distinct chemical states of the carboxyl group are considered: deprotonated (negatively charged), protonated (neutral), and esterified (neutral). The parametrization procedure was based on quantum-chemical calculations, and the resulting parameters were tested in the context of (i) flexibility of the pyranose rings under different pH conditions, (ii) conformation of the glycosidic linkage of the (1 → 4)-type for uronates with different chemical states of carboxyl moieties, (iii) conformation of the exocyclic (i.e., carboxylate and lactol) moieties, and (iv) structure of the Ca²⁺-linked chain–chain complexes of uronates. The presently proposed parameters in combination with the 56a6CARBO/CARBO_R set can be used to describe the naturally occurring polyuronates, composed either of homogeneous (e.g., glucuronans) or heterogeneous (e.g., pectins, alginates) segments. The results of simulations relying on the new set of parameters indicate that the conformation of glycosidic linkage is nearly unaffected by the chemical state of the carboxyl group, in contrary to the ring conformational equilibria. The calculations for the poly(α-d-galacturonate)–Ca²⁺ and poly(α-l-guluronate)–Ca²⁺ complexes show that both parallel and anitiparallel arrangements of uronate chains are possible but differ in several structural aspects.