Showing papers on "Pyranose published in 1997"
TL;DR: In this paper, a comparative study was made using IR and Raman spectroscopy of theoretical calculations of the vibrational spectra of a series of carbohydrates differing in the configuration of CO (CH) bonds in various positions of the pyranose ring.
117 citations
TL;DR: The authors showed that the conformation of the pyranose ring is crucially dependent on substitution pattern: the 2-azido altruronic acid derivatives prefer the 4 C 1 conformation whereas the 2acetamido congeners exist preferentially in the 1 C 4 conformation.
62 citations
TL;DR: In this paper, an AMBER-like force field for modeling oligosaccharides was proposed. But the parameters were developed from ab initio calculations on small model systems having structures characteristic of 1,2-, 1,3-, and 1,4-glycosidic linkages.
Abstract: In this paper we extend our previously reported parameterization of carbohydrates to an all-atom AMBER-like force field suitable for modeling oligosaccharides. Parameters were developed from ab initio calculations on small model systems having structures characteristic of 1,2-, 1,3-, and 1,4-glycosidic linkages and monosaccharides to give a complete parameter set for pyranose mono- and oligosaccharides. The accuracy of the parameter set was assessed by free energy calculations on various simple sugars and disaccharides. Solvent effects were included using the GB/SA continuum model for water. The sampling problem was solved for these systems by the recently described MC/SD and MC(JBW)/SD simulation methods that facilitate interconversion of conformational states. MC(JBW)/SD simulations were used to calculate anomeric free energies for tetrahydropyran derivatives and monosaccharides. All simulations rapidly converged to values in good agreement with the experimental results. MC/SD simulations were used to s...
60 citations
TL;DR: Pyranose 2-oxidase (P2O) was purified 43-fold to apparent homogeneity from the basidiomycete Phanerochaete chrysosporium using liquid chromatography on phenyl Sepharose, Mono Q and phenyl Superose.
Abstract: Pyranose 2-oxidase (P2O) was purified 43-fold to apparent homogeneity from the basidiomycete Phanerochaete chrysosporium using liquid chromatography on phenyl Sepharose, Mono Q (twice) and phenyl Superose. The native enzyme has a molecular mass of about 250 kDa (based on native PAGE) and is composed of four identical subunits of 65 kDa. It contains three isoforms of isoelectric point (pI) 5.0, 5.05 and 5.15 and does not appear to be a glycoprotein. P2O is optimally stable at pH 8.0 and up to 60 °C. It is active over a broad pH range (5.0–9.0) with maximum activity at pH 8.0–8.5 and at 55 °C, and a broad substrate specificity. d-Glucose is the preferred substrate, but 1-β-aurothioglucose, 6-deoxy-d-glucose, l-sorbose, d-xylose, 5-thioglucose, d-glucono-1,5-lactone, maltose and 2-deoxy-d-glucose are also oxidised at relatively high rates. A Ping Pong Bi Bi mechanism was demonstrated for the P2O reaction at pH 8.0, with a catalytic constant (kcat) of 111.0 s−1 and an affinity constant (Km) of 1.43 mM for d-glucose and 83.2 μM for oxygen. Whereas the steady-state kinetics for glucose oxidation were unaffected by the medium at pH ≥ 7.0, at low pH both pH and buffer composition affected the P2O kinetics with the kcat/Km value decreasing with decreasing pH. The greatest effect was observed in acetate buffer (0.1 M, pH 4.5), where the kcat decreased to 60.9 s−1 and the Km increased to 240 mM. The activity of P2O was completely inhibited by 10 mM HgCl2, AgNO3 and ZnCl2, and 50% by lead acetate, CuCl2 and MnCl2.
59 citations
TL;DR: In this paper, a route to epimeric carbon-linked glycoglycines that exploits the stereoselective addition of 2-lithiofuran and 2lithiothiazole to sugar nitrones has been described.
Abstract: A route to epimeric carbon-linked glycoglycines that exploits the stereoselective addition of 2-lithiofuran and 2-lithiothiazole to sugar nitrones has been described. The reaction occurs with opposite diastereofacial selectivity depending on whether the free nitrone or the diethyl aluminum chloride precomplexed derivative is employed. The resulting furyl or thiazolyl hydroxylamines are dehydroxylated to amines by the action of titanium(III) chloride. From these compounds the amino acids are revealed by the oxidative cleavage of the furan ring or by the conversion of the thiazole into the formyl group and oxidation to carboxylic acid. Compounds have been prepared wherein the α-amino acid moiety is installed at C-4 and C-1 of furanoses (ribo, manno, xylo, and lyxo) and at C-5 and C-1 of a pyranose (galacto).
56 citations
TL;DR: The structure of the carbohydrate backbone of the lipopolysaccharide from Acinetobacter strain ATCC 17905 was studied and all monosaccharide residues also possess the D-configuration and are present in the pyranose form.
Abstract: The structure of the carbohydrate backbone of the lipopolysaccharide from Acinetobacter strain ATCC 17905 was studied. After deacylation of the lipopolysaccharide, a mixture of two compounds (ratio approximately 2:1) was isolated by high-performance anion-exchange chromatography, the structures of which were determined by NMR spectroscopy and electrospray-mass spectrometry as [STRUCUTRE IN TEXT] [Sug, 3-deoxy-D-manno-2-octulopyranosonic acid (Kdo) in oligosaccharide 1 (major portion) and D-glycero-D-talo-2-octulopyranosonic acid (Ko) in oligosaccharide 2 (minor portion)]. All monosaccharide residues also possess the D-configuration and are present in the pyranose form.
53 citations
TL;DR: A new approach for the synthesis of amino sugars using an allyl======cyanate-to-isocyanate rearrangement has been developed in this paper, which involves introduction of the nitrogen substituent into the pyranose framework by [3,3] sigmatropic re-arrangement of allyl cyanate.
Abstract: A new approach for the synthesis of amino sugars using an allyl
cyanate-to-isocyanate rearrangement has been developed. The key feature
in this method involves introduction of the nitrogen substituent into
the pyranose framework by [3,3] sigmatropic
rearrangement of an allyl cyanate. Subsequent functionalization of the
allylamine moiety by either hydroxylation or cyclofunctionalization
completes the synthesis of two amino sugars,
D-perosamine and
D-vicenisamine.
49 citations
TL;DR: A novel C-2-specific sugar oxidoreductase, tentatively designated as pyranose 2-dehydrogenase, was purified 68-fold to apparent homogeneity from the mycelia of Agaricus bisporus, which expressed maximum activity of the enzyme during idiophasic growth in liquid media.
Abstract: A novel C-2-specific sugar oxidoreductase, tentatively designated as pyranose 2-dehydrogenase, was purified 68-fold to apparent homogeneity (16.4 U/mg protein) from the mycelia of Agaricus bisporus, which expressed maximum activity of the enzyme during idiophasic growth in liquid media. Using 1,4-benzoquinone as an electron acceptor, pyranose 2-dehydrogenase oxidized d-glucose to d-arabino-2-hexosulose (2-dehydroglucose, 2-ketoglucose), which was identified spectroscopically through its N,N-diphenylhydrazone. The enzyme is highly nonspecific. d-,l-Arabinose, d-ribose, d-xylose, d-galactose, and several oligosaccharides and glycopyranosides were all converted to the corresponding 2-aldoketoses (aldosuloses) as indicated by TLC. d-Glucono-1,5-lactone, d-arabino-2-hexosulose, and l-sorbose were also oxidized at significant rates. UV/VIS spectrum of the native enzyme (λmax 274, 362, and 465 nm) was consistent with a flavin prosthetic group. In contrast to oligomeric intracellular pyranose 2-oxidase (EC 1.1.3.10), pyranose 2-dehydrogenase is a monomeric glycoprotein (pI 4.2) incapable of reducing O2 to H2O2 (> 5 × 104-fold lower rate using a standard pyranose oxidase assay); pyranose 2-dehydrogenase is actively secreted into the extracellular fluid (up to 0.5 U/ml culture filtrate). The dehydrogenase has a native molecular mass of ∼79 kDa as determined by gel filtration; its subunit molecular mass is ∼75 kDa as estimated by SDS-PAGE. Two pH optima of the enzyme were found, one alkaline at pH 9 (phosphate buffer) and the other acidic at pH 4 (acetate buffer). Ag+, Hg2+, Cu2+, and CN– (10 mM) were inhibitory, while 50 mM acetate had an activating effect.
45 citations
TL;DR: The tungsten pentacarbonyl-induced cyclization of an acyclic alkynol substrate bearing protected oxygen and nitrogen functional groups provides the cyclic Tungsten oxacarbene, which is readily converted into a pyranose glycal structurally related to the carbohydrate moieties of the pluramycin and vancomycin families of antitumor antibiotics as mentioned in this paper.
45 citations
TL;DR: The 2-F and 4-F Gal-UDP derivatives I and II do not inhibit the enzyme galactopyranose mutase in the direction pyranoses → furanose but both compounds have been found to inhibit the reverse reaction.
Abstract: A novel latent→active phosphorylation strategy has
been employed
for the preparation of two fluorinated nucleoside diphosphates
(compounds I and II). The strategy is based on the isomerisation of
substituted allyl to vinyl glycosides which were subsequently
phosphorylated by treatment with dibenzyl hydrogen phosphate,
N-iodosuccinimide and a catalytic amount of trimethylsilyl
triflate. This methodology is very suitable for the preparation of
nucleoside diphosphates that have a modification in the saccharide
moiety since the allyl moiety serves first as an anomeric protecting
group, allowing for protecting-group manipulation and functionalisation
of the sugar ring, but after isomerisation to the corresponding vinyl
glycoside it acts as an anomeric leaving group. The 2-F and 4-F Gal-UDP
derivatives I and II do not inhibit the enzyme galactopyranose mutase in
the direction pyranose → furanose but both compounds
have been found to inhibit the reverse reaction.
35 citations
TL;DR: Partial hydrolysis of the nitrile moiety in acetylated 1-bromo-glycopyranosyl cyanides 1 and 9 mediated by TiCl4 gave C-(1-Bromo, 1-deoxy-GCL)formamides 2 and 10 whose reaction either with AgOCN, AgSCN or KSCN in nitromethane resulted in the formation of glycopyranoylidene-spirohydantoins 3, 11 and 15 and -thiohydantoin 7 and 16 as mentioned in this paper.
TL;DR: In this paper, a general synthesis of derivatives of tetrodialdoses and pentodial-doses in furanose or pyranose form is described, and a general formulation of derivatives in the form of tetrosynthetic derivatives is given.
TL;DR: The length of the fatty acid side chain in the ceramide portions greatly affects the immunostimulatory effects of α-galactosylceramides and α-GluCers and the configuration of the 4″-hydroxyl group of the inner pyranose moiety plays an important role in the Immunostimulation effects of monoglycosylated α- d -pyranosylcer amides.
TL;DR: It is suggested that the conformational changes observed in bound FK506 are induced by the interaction between the 80's loop of FKBP12 and the pyranose ring of FkBP12, which result in the formation of a complex with the both correct shape and surface polarity for interaction with calcineurin.
TL;DR: Nine 3-morpholino derivatives were prepared, including a disaccharide analog of N-acetyllactosamine where the nitrogen of glycine was inserted into the galactose ring and was an excellent substrate for a mild fucosyltransferase which converted it to a novel functionalized LeX mimic.
Abstract: Periodate oxidation of glycopyranosides yields dialdehydes that can be reductively aminated in the presence of amino acids to produce hybrid glycopeptides where the amino acid nitrogen is inserted into the resulting 2,4-dideoxypyranoside at position 3. Nine such 3-morpholino derivatives were prepared, including a disaccharide analog of N-acetyllactosamine (β-Gal(1→4)βGlcNAc) where the nitrogen of glycine was inserted into the galactose ring. The resulting hybrid disaccharide was an excellent substrate for a mild fucosyltransferase which converted it to a novel functionalized LeX mimic.
TL;DR: The integrity of doxorubicin and the connectivity between the drug and peptidyl chain was successfully confirmed in spite of the comparatively low abundance of the corresponding monomeric units and of signal spreading due to the diastereomeric mixture of peptidol chains.
Abstract: Two poly-2-hydroxypropylmethacrylamide conjugates with the anti-cancer drug doxorubicin were investigated by1H NMR spectroscopy. In both polymers (FCE 28068 and FCE 28069) the drug is connected to a polymethacrylamide backbone via a tetrapeptidyl spacer (Gly-L,D-Phe–L-Leu–Gly) and, in addition, FCE 28069 contains similarly bound D-galactosamine molecules as liver-targeting moieties. Signals of the drug and galactosamine protons were fully assigned in the spectra of the polymers by means of NOESY and TOCSY experiments and by comparison with the spectra of reference compounds. The integrity of doxorubicin and the connectivity between the drug and peptidyl chain was successfully confirmed in spite of the comparatively low abundance (<5%) of the corresponding monomeric units and of signal spreading due to the diastereomeric mixture of peptidyl chains. Polymer-bound galactosamine molecules were found to be distributed among four isomeric forms (α- and β-anomers of pyranose and furanose forms, with predominance of the α-pyranose form). Diagnostic signals for possible alternative peptidyl chain endings (2-hydroxypropylamide or free carboxyl groups) were identified with the help of model polymers and the first, but not the second, were detected in the spectra of the two FCEs. In addition to the above results, high-field NMR is a rapid and sensitive method for the qualitative identification of low molecular weight contaminants in production batches of polymer–drug conjugates. © 1997 by John Wiley & Sons, Ltd.
TL;DR: In this article, primary amines reacted upon 4,6-ditosylates of glucopyranosides to give an azetidine ring fused on C-4 and C-6 of the pyranose ring.
TL;DR: Staudinger reaction of acetylated (1 R )-1-azido-D-galactopyranosyl cyanide with triphenylphosphine in diethyl ether led to the isolation of a crystalline phosphazide (2 ), unprecedented in carbohydrate chemistry as mentioned in this paper.
TL;DR: In this article, the reaction of azido sugars with triphenylphosphine and carbon dioxide leading to cyclic carbamates has been studied by means of PM3 semi-empirical quantum chemical computations to elucidate the detailed mechanisms of chemical processes involved in this transformation.
Abstract: The reaction of azido sugars with triphenylphosphine and carbon dioxide leading to cyclic carbamates has been studied by means of PM3 semiempirical quantum chemical computations to elucidate the detailed mechanisms of chemical processes involved in this transformation. Our results clearly indicate that the mechanism involving an isocyanate intermediate is preferred for both α- and β-anomers. In addition, we find that, in the case of the α-anomer, steric hindrance prevents the occurrence of direct cyclization and requires the opening of the pyranose ring, in contrast to the case of the β-anomer. This result explains the poor yield and the occurrence of three isomeric cyclic carbamates when the reaction is performed on the α- anomer.
TL;DR: The push-pull-activated pyranosidulose 2 reacted with acetylacetone and methyl acetoacetate to afford the anellated pyranoides 3 and 4, respectively as discussed by the authors.
Abstract: The push-pull-activated pyranosidulose 2 reacted with acetylacetone and methyl acetoacetate to afford the anellated pyranosides 3 and 4, respectively. Treatment of the ulose 2 with acetoacetamide and malononitrile, respectively, furnished the fused pyridones 5 and 6. Benzo-anellated pyranosides 7 were obtained by reaction of pyranosidulose 2 with dialkyl 3-oxoglutarates.
TL;DR: In this article, the isomeric mixture of 5 in D2O solution was carefully examined using 1H and 13C NMR techniques and structural assignments were made for seven isomers.
TL;DR: Pyranoside 3, 4-cis-thionocarbonates, under radical-promoted reaction conditions (method A, B, or C, described in the text), gave O-S rearrangement products, 3-4-thiol carbonates of cis-stereochemistry, in accepTable yields as discussed by the authors.
Abstract: Pyranoside 3, 4-cis-thionocarbonates, under radical-promoted reaction conditions (method A, B, or C, described in the text), gave O-S rearrangement products, 3, 4-thiolcarbonates of cis-stereochemistry, in accepTable yields.2, 3-Thionocarbonates of trans-stereochemistry also gave the rearrangement products of cis-stereochemistry preferentially in method B (photolysis with hexabutyldistannane). Although regio-control of the product was not satisfactory in most cases, some of the results suggested that the regioselectivity of the reaction is markedly influenced by the stereochemistry of the anomeric position of the substrates. The products were converted to thioglycosides(peracetate forms) by conventional means.
TL;DR: In this paper, the pyranose ring adopts the usual 4 C 1 (D) conformation and the N-acetyl group exists in the Z-anti conformation.
Abstract: In the title molecule, C 8 H 15 NO 6 , the pyranose ring adopts the usual 4 C 1 (D) conformation and the N-acetyl group exists in the Z-anti conformation. The orientation of the primary alcohol group is gauche.
TL;DR: The calculated glycosidic torsion angles of the lowest free energy conformation of GA1 in the hydrated state are in accord with the structures of relevant oligosaccharides deduced from nmr experiments and hard sphere exoanomeric calculations, suggesting that the medium- and long-range interactions are also of consequence.
Abstract: In order to investigate the significance of preferred conformations of the saccharide for the steric orientation and recognition of glycosphingolipids at the membrane surface, the conformational free energy calculations were carried out on the asialo-GM1 [GA1; beta-D-Gal (1-->3) beta-D-GalNac(1-->4) beta-D-Gal(1-->4) beta-D-Glc-O-ceramide) using a new program CONCARB (CONformational study program for CARBohydrate) in the unhydrated and hydrated states. The overall backbone conformational of GA1 appears to be extended with a little bent at the glycosidic II-III linkage, in which two pyranose rings of Gal(IV)-GalNAc-(III) moiety orient approximately perpendicular to those of Gal(II)-Glc(I) moiety. This is consistent with the structures deduced from high-sensitivity differential scanning calorimetry experiments and the nmr study on GA1. The calculated glycosidic torsion angles of the lowest free energy conformation of GA1 in the hydrated state are in accord with the structures of relevant oligosaccharides deduced from nmr experiments and hard sphere exoanomeric calculations. A comparison of the values of glycosidic torsion angles phi and psi of GA1 and its constituent oligosaccharides indicates that the overall backbone conformation of each oligosaccharide is retained when the oligosaccharide chain becomes longer. This implies that the short-range interactions between the nearest-neighbored saccharides are of significant importance in stabilizing the overall backbone conformation of GA1 in both the unhydrated and hydrated states. The different orientation and hydrogen bonds of hydroxymethyl and hydroxyl groups from one oligosaccharide to another suggest that the medium- and long-range interactions are also of consequence. Hydration seems to affect significantly the confirmation of these groups, but not to perturb remarkably the overall backbone conformation of GA1.
TL;DR: In this paper, the preferred conformations of sucrose, 2-O -acetylsucrose and 2- O -lauroyl sucrose have been explored with the MM3 force field.
TL;DR: In this article, the synthesis of disodium (6-deoxy-α-D-ribo-hexopyran-3-ulosyl) (2′-deoxythymidin-5′-yl) diphosphate (1) is described.
Abstract: The synthesis of disodium (6-deoxy-α-D-ribo-hexopyran-3-ulosyl) (2′-deoxythymidin-5′-yl) diphosphate (1) is described. To this end, D-glucose is transformed into known furanose derivative 2 possessing a 3-C-methylene group as latent functionality for 3-ulose generation. From 2, 3,6-dideoxy derivative 6 was synthesized; ensuing acid catalyzed cleavage of the 1,2-O-isopropylidene group and then O-acetylation furnished the required pyranose 8α,β, which could be selectively deacetylated at the anomeric oxygen to afford 9α,β. Treatment with phosphitylating agent 13e and then oxidation led to dibenzylphosphate derivative 15e which could be chemoselectively debenzylated by hydrogenolysis without affecting the olefinic double bond ( 17); de-O-acetylation and then ozonolysis afforded the unprotected phosphate intermediates 18 and 19, respectively. Both compounds could be successfully used for the synthesis of 1 by employing the nucleoside phosphate morpholidate procedure for the generation of nucleoside diphosphate sugars. Ozone cleavage of the olefinic double bond in 20 could be successfully performed even in the presence of the thymine moiety.
TL;DR: In this article, 2-Aminoethylimines and 3-aminopropylimines of aldoses have been synthesized and their structure in solutions has been investigated by 13C NMR spectroscopy.
TL;DR: The furanoid structures of the KDN moiety were supported by with 1H-NMR experiments, and the reaction was considered as a novel glycosylation with ring contraction, which proceeded via in situ pyranose-furanose rearrangement of theK DN moiety, and subsequent coupling with acceptors.
Abstract: In studies on the glycosylation of 3-deoxy-D-glycero-D-galacto-2-nonulosonic acid (KDN) derivatives, O-glycosides of furanose-type KDN were synthesized from benzyl 4, 5, 7, 8, 9-penta-O-acetyl-2-bromo-2, 3-dideoxy-D-glycero-D-galacto-2-nonulopyranosonate under Koenigs-Knorr reaction conditions. The furanoid structures of the KDN moiety were supported by with 1H-NMR experiments, and the reaction was considered as a novel glycosylation with ring contraction, which proceeded via in situ pyranose-furanose rearrangement of the KDN moiety, and subsequent coupling with acceptors.
TL;DR: In this article, the Barton-McCombie reaction was used to convert maltosyl-(1 → 4)-α,α-trehalose derivative to 3-deoxygenated tetrasaccharide.
TL;DR: The 4,5-dideoxy-D-arabino-oct-2-ulosonate bromide donor and the acceptor under Helferich conditions gave the propyl glycosides, which may be used for binding studies with Chlamydia-specific and cross-reactive, Kdospecific monoclonal antibodies.
Abstract: Deoxy analogues of the Chlamydia-specific, α-(2→8)-linked Kdo disaccharide epitope modified at the pyranose ring of the terminal Kdo unit have been prepared. Utilizing the 3,5-dideoxy-D-arabino-oct-2-ulosonate bromide donor [1] and the acceptor [2] under Helferich conditions, the 5-deoxy-α-Kdo-(2→8)-α-Kdo disaccharide [3] was obtained as the minor product together with unsaturated, α-(2→8)-glycosidically and (4→8)-ether-linked derivatives [5] and [7] as the major components. Deprotection afforded the disaccharide allyl glycosides [4], [6], and [8]. Further transformation of protected intermediates by hydrogenation followed by deblocking gave the propyl glycosides [12], [14] and [17]. The compounds may be used for binding studies with Chlamydia-specific and cross-reactive, Kdospecific monoclonal antibodies.