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Showing papers on "Pyranose published in 2002"


Journal ArticleDOI
TL;DR: Vicinal, equatorial OH groups in the (4)C(1) conformer of glucopyranose are, however, able to form strong bidentate hydrogen bonds with water molecules in a cooperative manner, each water molecule acting simultaneously as both hydrogen bond donor and acceptor.
Abstract: Topological analysis of the electron density profiles and the atomic basin integration data for the most energetically favorable 4C1 and 1C4 conformers of β-d-glucopyranose, calculated at the B3LYP/6-31+G(d), MPWlPW91/6-311+G(2d,p), and MP2/6-31+G(d) levels, demonstrates that intramolecular hydrogen bonding between adjacent ring OH groups does not occur in glucopyranose, given the need to demonstrate a bond critical point (BCP) of correct (3,−1) topology for such an interaction to be termed a hydrogen bond. On the other hand, pyranose ring OH groups separated by three, rather than just two, carbon atoms are able to form an intramolecular hydrogen bond similar in topological properties and geometry to that found for propane-1,3-diol. Vicinal, equatorial OH groups in the 4C1 conformer of glucopyranose are, however, able to form strong bidentate hydrogen bonds with water molecules in a cooperative manner, each water molecule acting simultaneously as both hydrogen bond donor and acceptor, and characterized by...

105 citations


Journal ArticleDOI
TL;DR: A strategy to design face discriminated glycosyl donors that exist predominantly in only one family of conformers is proposed based on observations of high beta-stereoselectivity of mannopyranosyl donors and high alpha-stirring of glucopyranoyl donors with the 4,6-O-benzylidene protecting groups.

96 citations


Journal ArticleDOI
TL;DR: In this article, the gas phase structures of five carbon monosaccharides (d-ribose, d-lyxose, 2-deoxy-dribose and d-arabinose) were studied via ion−molecule reactions with dimethoxyphosphenium ion and 1,3-dioxolane-2-phosphensium ion in a Fourier transform ion cyclotron resonance mass spectrometer.
Abstract: The gas-phase structures of five five-carbon monosaccharides (d-ribose, d-lyxose, 2-deoxy-d-ribose, d-xylose, and d-arabinose) were studied via ion−molecule reactions with dimethoxyphosphenium ion and 1,3-dioxolane-2-phosphenium ion in a Fourier transform ion cyclotron resonance mass spectrometer. These reagent ions have been earlier demonstrated to be sensitive to the three-dimensional structures of diastereomeric vicinal diols. They were found to display unique reactivity toward each monosaccharide. The results indicate that the gaseous monosaccharides are cyclic molecules. On the basis of a comparison of the reactions of monosaccharides introduced into the gas phase via two different methods, laser-induced acoustic desorption (LIAD) and thermal desorption, the monosaccharides are concluded to maintain their crystalline structure, a pyranose form, throughout the evaporation procedure. For all the monosaccharides in this study except for d-lyxose, the lowest-energy structure found computationally using d...

75 citations


Journal ArticleDOI
TL;DR: In this article, the authors present a systematic study on the factors that determine the formation of a well-defined intramolecular H-bonding network between carbohydrate hydroxy groups, and its cooperative or anti-cooperative influence on selected intermolecular processes mediated by H bonds.

65 citations


Journal ArticleDOI
TL;DR: Data suggest that substitution of a secondary amine group to replace the C-6 (or C-1) -OH of 2,5-anhydro-D-mannitol results in compounds of high affinity; the affinity is enhanced over 10-fold compared with D-fructose.
Abstract: The GLUT5 transporter catalyses the specific uptake of D-fructose and can accept this hexose in its furanose and pyranose ring forms. The transporter does not accept fructose epimers and has very limited tolerance of bulky groups substituted at the 2-, 3-, 4- and 5-OH positions [Tatibouet, Yang, Morin and Holman (2000) Bioorg. Med. Chem. 8, 1825-1833]. To further explore whether bulky groups can be tolerated at the primary OH positions, a D-fructose analogue with an allylamine group substitution to replace the 1-OH group was synthesized and was found to be quite well tolerated ( K (i)=27.1 mM). However, this analogue occurs in multiple ring forms. By contrast, 2,5-anhydro-D-mannitol is a symmetrical molecule that occurs only in a furanose ring form in which C-1 and C-6 are equivalent. We have therefore synthesized new 2,5-anhydro-D-mannitol analogues (substituted at the equivalent of the 6-OH of D-fructose) and from studies in Chinese hamster ovary cells expressing GLUT5 cells report that (i) the allylamine derivative of 2,5-anhydro-D-mannitol is well tolerated ( K (i)=2.66 mM); (ii) introduction of a di-nitrophenyl-substituted secondary amine group enhances affinity ( K (i)=0.56 mM); (iii) introduction of amide-linked biotinylated photolabel moieties is possible without loss of affinity relative to 2,5-anhydro-D-mannitol but a small secondary amine spacer between the biotinylated photolabelling moiety and the fructofuranose ring increases affinity (fructose photolabel 2; K (i)=1.16 mM); (iv) introduction of a hydrophilic tartarate spacer between biotin and the diazirine photoreactive groups can be accomplished without reduction in affinity and (v) photoactivation of biotinylated fructose photolabels leads to specific biotin tagging of GLUT5. These data suggest that substitution of a secondary amine group (-NH) to replace the C-6 (or C-1) -OH of 2,5-anhydro-D-mannitol results in compounds of high affinity; the affinity is enhanced over 10-fold compared with D-fructose.

58 citations



Journal ArticleDOI
TL;DR: In this paper, a variety of homochiral carbohydrate-derived thiols have been prepared and characterised, in which the SH group is attached to the anomeric carbon atom, and they have been evaluated as protic polarity-reversal catalysts to mediate the enantioselective radical-chain addition of triphenylsilane to the H2CCR1R2 group in prochiral methylenelactones to give chiral adducts of the general type Ph3SiCH2CHR 1R2.
Abstract: A variety of novel homochiral carbohydrate-derived thiols, in which the SH group is attached to the anomeric carbon atom, have been prepared and characterised. These thiols have been evaluated as protic polarity-reversal catalysts to mediate the enantioselective radical-chain addition of triphenylsilane to the H2CCR1R2 group in prochiral methylenelactones to give chiral adducts of the general type Ph3SiCH2CHR1R2; chemical yields were uniformly high. Systematic changes in the structures of the thiols were made with the aim of increasing the enantioselectivity of hydrogen-atom abstraction from the SH group by the prochiral alkyl radical Ph3SiCH2ĊR1R2. Although adducts could be obtained in high enantiomeric excess in reactions carried out at 60 °C, no significant improvement in enantioselectivity could be achieved over that obtainable using simple tetra-O-acetyl-β-glucopyranose and -β-mannopyranose thiols as catalysts. It was found that the α-anomers of the pyranose thiols were ineffective at mediating enantioselective hydrogen-atom transfer to the radical Ph3SiCH2ĊR1R2. All the β-pyranose thiols gave asymmetric induction in the same sense, but two β-mannofuranose thiols with less polar substituents gave asymmetric induction in the opposite sense. It is concluded that both steric and dipole–dipole interactions between the prochiral carbon-centred radical and the thiol are important in determining enantioselectivity and that these interactions can act in opposition as well as co-operatively; solvent effects are also shown to be important.

49 citations


Journal ArticleDOI
TL;DR: In this paper, the formation of Zn-enolate that is stabilized by intramolecular chelation to the pyranose ring-oxygen to form a syn chairboat structure was shown to be a useful method for the preparation of manno-β-C-glycosides.
Abstract: 2‘-Aldehydes and 2‘-ketones of α-C-glycosides, including the gluco-, galacto-, and manno- series, were epimerized exclusively to their β-anomers in good-to-excellent yields under basic conditions and in the presence of zinc acetate. The β-stereoselectivity is independent of the neighboring group at 2-O-substitution of sugar substrates. Therefore, this provides a particularly useful method for the preparation of manno-β-C-glycosides. The epimerization is likely initiated by the formation of Zn-enolate that is stabilized by intramolecular chelation to the pyranose ring-oxygen to form a syn chair-boat structure. Due to the activation generated by the Zn−O coordination, fission of the C1−O bond occurs, leading to opening of the pyranose ring, which is spontaneously followed by a change in conformation. The more stable anti chair-boat transition state is favored, and the subsequent hetero-intramolecular Michael addition results in the formation of β-C-glycoside in a ring-closure step.

47 citations


Journal ArticleDOI
TL;DR: The quinone-dependent pyranose dehydrogenase purified from mycelial extracts of the basidiomycete fungus Agaricus meleagris catalyzed oxidation of the non-reducing oligosaccharides sucrose, melezitose and erlose at C-3 of their terminal glucopyranosyl moiety.
Abstract: The quinone-dependent pyranose dehydrogenase (PDH) purified from mycelial extracts of the basidiomycete fungus Agaricus meleagris catalyzed oxidation of the non-reducing oligosaccharides sucrose, melezitose and erlose at C-3 of their terminal glucopyranosyl moiety while α,α-trehalose was double oxidized at both C-3 and C-3′. Analogously, using MS and in situ NMR spectroscopy, formation of C-3 carbonyl derivatives was also demonstrated with methyl-α- d -Glcp, methyl-β- d -Glcp and methyl-α- d -Galp. Yields of conversions performed at room temperature with 10 mM sugars and 1,4-benzoquinone as an electron acceptor in non-buffered systems were ≥90% within 3–20 h, depending on substrate.

28 citations


Journal ArticleDOI
TL;DR: The isomeric composition of D-glucosone 6-phosphate in aqueous solution was quantitatively determined by NMR spectroscopy and compared to D- GLUCosone.

22 citations


Journal ArticleDOI
TL;DR: The presence of three aromatic groups in the pyranose ring resulted essential for NK-2 affinity, while an increase in activity was shown by the corresponding sulfoxides.

Journal ArticleDOI
TL;DR: The observed variation in pyranose ring conformations in product compounds is explained in terms of C-2 substitution.

Journal ArticleDOI
TL;DR: In this paper, the authors studied the ring conformations of d-xylopyranose, d-lyxopyrnose, and d-arabinopyrynose and found that the energy surfaces exhibit low-energy regions corresponding to chair and skew forms with high energy barriers between these regions.

Journal ArticleDOI
TL;DR: Reaction of α-lithiated methyl glyoxylate diethyl mercaptal with 2,3,5-tri-O-benzyl-D-arabinose stereoselectively afforded the D-gluco-2-heptulosonate derivative 4, and the second target molecule, 1b, was obtained in just a few steps.

Journal ArticleDOI
TL;DR: In this article, a useful catalyst for the reductive elimination of acylated glycosyl bromides to form glycals, both in the pyranose and furanose series, using zinc/ammonium chloride/methanol or zinc/acetic acid/acetonitrile.
Abstract: Ethylene-N,N-bis(salicylideneiminato)oxovanadium(IV) {VO(salen)} has been developed as a useful catalyst for the reductive elimination of acylated glycosyl bromides to form glycals, both in the pyranose and furanose series, using zinc/ammonium chloride/methanol or zinc/acetic acid/acetonitrile.

Journal ArticleDOI
Kegang Liu1, Shou-Gang Hu1, Yikang Wu1, Zhu-Jun Yao1, Yu-Lin Wu1 
TL;DR: Based on the oxidation of corresponding terminal alkynes to α-keto esters, DAH (3-deoxy-D-arabino-hept-2-ulosonic acid) in its pyranose-furanose mixture form was efficiently synthesized as discussed by the authors.
Abstract: Based on the oxidation of corresponding terminal alkynes to α-keto esters, DAH (3-deoxy-D-arabino-hept-2-ulosonic acid) in its pyranose form and DRH (3-deoxy-D-ribo-hept-2-ulosonic acid) in its protected pyranose–furanose mixture form were efficiently synthesized. These terminal alkynes were in turn obtained by C1- or C3-homologation of corresponding protected sugars, respectively. Along with the application of this strategy, the syntheses of two C6-ulosonic acids, 3-deoxy-D-erythro-hex-2-ulosonic acid and 3-deoxy-L-erythro-hex-2-ulosonic acid in their protected pyranose form, were also described.

Journal ArticleDOI
TL;DR: In this paper, the influence of the size of the perfluoroalkyl groups attached to C-2 on the furanose/pyranose as well as on the α-furanoses/β-fursansose and α-pyransose/β -pyranosose ratio in solution was studied.

Journal ArticleDOI
TL;DR: Intramolecular Friedel-Crafts cyclization of 2-O-benzyl ethers at a model pyranose acetal is activated by incorporation of a trimethylsilyl group, albeit via unexpected, presumably steric means.


Journal ArticleDOI
TL;DR: In this article, the crystal and molecular structures of ammonium (1a) and potassium (1b) salts of diisopropylidene derivative and ammonium(2) salt of monoisoprocessor derivative were determined by X-ray crystallography.

Journal ArticleDOI
TL;DR: A novel sugar constituent was isolated from the heteropolysaccharide excreted by Streptococcus thermophilus 8 S when grown in skimmed milk and was shown to be 6-O-(3',9'-dideoxy-D-threo- D-altro-nononic acid-2'-yl)-D-glucopyranose.
Abstract: A novel sugar constituent was isolated from the heteropolysaccharide excreted by Streptococcus thermophilus 8 S when grown in skimmed milk. The structure and absolute configuration were determined by means of chemical analysis, mass spectrometry, NMRspectroscopy, along with molecular dynamics simulations, and was shown to be 6-O-(3,9-dideoxy--threo--altro-nononic acid-2-yl)--gluco- pyranose.

Journal ArticleDOI
TL;DR: Novel bridging nucleoside analogues were prepared by cycloaddition reactions between pyranose glycals and barbiturate-derived, reactive thionoimides in modest yields and several of the compounds showed moderate activities against HIV-1 in primary human lymphocytes.

Journal ArticleDOI
TL;DR: The overall conformation of the title compound, C13H24O10, is described by the glycosidic torsion angles φH (H1g −C1g-O2r-C2r) and ψH (C 1g −O 2r-O 2R-C 2r −16.1°, respectively as discussed by the authors.
Abstract: The overall conformation of the title compound, C13H24O10, is described by the glycosidic torsion angles φH (H1g—C1g—O2r—C2r) and ψH (C1g—O2r—C2r—H2r), which have values of 13.6 and 16.1°, respectively. The former is significantly different from the value predicted by consideration of the exo-anomeric effect (φH ∼ 60°) and from that in solution (φH ∼ 50°), as determined previously by NMR spectroscopy. An intramolecular O3r—H⋯O2g hydrogen bond may help to stabilize the conformation in the solid state. The orientation of the hydroxy­methyl group of the glucose residue is gauche–gauche, with a torsion angle ω (O5g—C5g—C6g—O6g) of −70.4 (4)°. Both pyranose rings are in their expected chair conformations, i.e. 4C1 for d-glucose and 1C4 for l-rhamnose.

Journal ArticleDOI
TL;DR: In this paper, the formation of Zn-enolate that is stabilized by intramolecular chelation to the pyranose ring-oxygen to form a syn chairboat structure was shown to be a useful method for the preparation of manno-β-C-glycosides.
Abstract: 2‘-Aldehydes and 2‘-ketones of α-C-glycosides, including the gluco-, galacto-, and manno- series, were epimerized exclusively to their β-anomers in good-to-excellent yields under basic conditions and in the presence of zinc acetate. The β-stereoselectivity is independent of the neighboring group at 2-O-substitution of sugar substrates. Therefore, this provides a particularly useful method for the preparation of manno-β-C-glycosides. The epimerization is likely initiated by the formation of Zn-enolate that is stabilized by intramolecular chelation to the pyranose ring-oxygen to form a syn chair-boat structure. Due to the activation generated by the Zn−O coordination, fission of the C1−O bond occurs, leading to opening of the pyranose ring, which is spontaneously followed by a change in conformation. The more stable anti chair-boat transition state is favored, and the subsequent hetero-intramolecular Michael addition results in the formation of β-C-glycoside in a ring-closure step.


Patent
09 May 2002
TL;DR: In this paper, a method for detecting a solid structural isomer of a sugar having a pyranose ring was proposed, in which the number of ring-consisting atoms is 6 and the carbon atom of the consisting atoms has the substituent electrically more negative than that, in order to obtain a J-coupling constant nJC,H (n is 2 or 3) between carbon and hydrogen nuclei separated by three or less couplings.
Abstract: PROBLEM TO BE SOLVED: To provide a novel NMR analysis method for detecting (assigning) a solid structural isomer of a compound having a non-aromatic cyclic structure, in which the number of ring- constituting atoms is 6 and a carbon atom of the ring-consisting atoms has an electrically more negative substituent, particularly a method for detecting a solid structural isomer of a sugar having a pyranose ring. SOLUTION: According to this method for detecting the solid structural isomer of the non-aromatic cyclic structure compound, in which the number of ring-consisting atoms is 6 and the carbon atom of the consisting atoms has the substituent electrically more negative than that, in order to obtain a J-coupling constant nJC,H (n is 2 or 3) between carbon and hydrogen nuclei separated by three or less couplings, a mixing time is set so that only information on spin coupling with the hydrogen separated from the carbon consisting the ring by three or fewer couplings appears on a two-dimensional chart, and an HETLOC two-dimensional NMR spectral chart is formed through measurements. A structure of the solid structural isomer of the compound, having the number of ring-consisting atoms of 6, is determined by conforming positive/negative codes, or positive/negative codes and absolute values of nJC,H values obtained from a deviation in an F2 axis direction of pairing correlative peaks, separated by 145-175 Hz in an F1 axis direction on the chart, matched in accordance with an nJC,H index.

Journal ArticleDOI
TL;DR: In this paper, the synthetic properties of homogeneous endo-and/or/1,3-glucanase G A from Cellulomonas cellulans were studied. But none of the acceptors had the equatorial substituents of the pyranose ring.
Abstract: The synthetic properties of homogeneous endo- g -1,3-glucanase G A from Cellulomonas cellulans were studied. Thirty-one synthetic and natural f - and g -glycosides were examined as acceptor molecules in transglycosylation reactions conducted in an aqueous-organic solvent environment with g -1,3-glucan as a polymeric donor. Seventeen acceptors underwent significant glycosylation. The best acceptors for glucanase G A were f - or g -glycosides that, in the favoured chair conformation of the pyranose ring, had all the equatorial substituents. Glycosides having an axial 4-hydroxyl or 2-hydroxyl group in the pyranose ring represent a poor class of acceptors.

Patent
19 Feb 2002
TL;DR: In this article, the problem of providing a gelling agent of an organic solvent, capable of being applied to a wide kind of organic solvents to form a strong gel is addressed.
Abstract: PROBLEM TO BE SOLVED: To provide a gelling agent of an organic solvent, capable of being applied to a wide kind of organic solvents to form a strong gel. SOLUTION: This gelling agent of the organic solvent comprises a cholesterol derivative represented by general formula (1) (wherein, one of R1 and R2 is a sugar residue, and the other is a hydrogen atom. Preferably R1 is the sugar residue containing a pyranose ring having at least one axial hydroxy group, and especially preferably the sugar is a monosaccharide selected from α- galactose, β-galactose, α-mannose and α-glucose).

Journal ArticleDOI
TL;DR: In this paper, a variety of homochiral carbohydrate-derived thiols have been prepared and characterised, in which the SH group is attached to the anomeric carbon atom, and they have been evaluated as protic polarity-reversal catalysts to mediate the enantioselective radical-chain addition of triphenylsilane to the H2CCR1R2 group in prochiral methylenelactones to give chiral adducts of the general type Ph3SiCH2CHR 1R2.
Abstract: A variety of novel homochiral carbohydrate-derived thiols, in which the SH group is attached to the anomeric carbon atom, have been prepared and characterised. These thiols have been evaluated as protic polarity-reversal catalysts to mediate the enantioselective radical-chain addition of triphenylsilane to the H2CCR1R2 group in prochiral methylenelactones to give chiral adducts of the general type Ph3SiCH2CHR1R2; chemical yields were uniformly high. Systematic changes in the structures of the thiols were made with the aim of increasing the enantioselectivity of hydrogen-atom abstraction from the SH group by the prochiral alkyl radical Ph3SiCH2ĊR1R2. Although adducts could be obtained in high enantiomeric excess in reactions carried out at 60 °C, no significant improvement in enantioselectivity could be achieved over that obtainable using simple tetra-O-acetyl-β-glucopyranose and -β-mannopyranose thiols as catalysts. It was found that the α-anomers of the pyranose thiols were ineffective at mediating enantioselective hydrogen-atom transfer to the radical Ph3SiCH2ĊR1R2. All the β-pyranose thiols gave asymmetric induction in the same sense, but two β-mannofuranose thiols with less polar substituents gave asymmetric induction in the opposite sense. It is concluded that both steric and dipole–dipole interactions between the prochiral carbon-centred radical and the thiol are important in determining enantioselectivity and that these interactions can act in opposition as well as co-operatively; solvent effects are also shown to be important.

Journal ArticleDOI
TL;DR: In this article, a series of anomeric nitrate esters and N-phthalimido glycosides of carbohydrates in furanose and pyranose forms have been synthesized in order to generate the corresponding alkoxy radicals and study the C1−C2 fragmentation reaction under reductive conditions.
Abstract: A series of anomeric nitrate esters and N-phthalimido glycosides of carbohydrates in furanose and pyranose forms have been synthesized in order to generate the corresponding alkoxy radicals and study the C1−C2 fragmentation reaction under reductive conditions. This reaction constitutes a two-step method for the transformation of carbohydrates into the corresponding alditols with one less carbon. Using this methodology, interesting four- and five-carbon building blocks for natural products synthesis possessing d-erythritol, d-threitol, d-xylitol, and d-arabinitol stereochemistry have been prepared. The synthesis of 1,2-O-isopropylidene-β-l-threose (40) and 1-acetamido-2,4,5-tri-O-acetyl-d-arabinitol (50) have also been achieved from 1,2:5,6-di-O-isopropylidene-β-d-glucofuranose and 2-acetamido-3,4,6-tri-O-acetyl-2-deoxy-d-glucopyranose, respectively.