Showing papers on "Pyranose published in 1987"
100 citations
TL;DR: Ammonium 3-deoxy-D-manno-2-octulosonate monohydrate (KDO) crystallizes in the orthorhombic space group P212121, and the cell dimensions are a - 6.9700(4)A, b = 7.7230(4), c = 23.4067 (12) A.
70 citations
TL;DR: 2H-NMR spin lattice relaxation times have been used to probe the head group motions of the glycolipids and indicate that the rate of head group motion increases in the order alpha-DTML less than alpha- DTGL less than beta-DTGL.
64 citations
TL;DR: Results indicate that beta-galactosidase probably destabilizes its substrate into a planar conformation of some type and that the galactose in the transition state may, therefore, also be quite planar.
Abstract: Various sugars and their lactones were tested for their inhibition of beta-galactosidase (Escherichia coli). L-Ribose, which in the furanose form has a hydroxyl configuration similar to that of D-galactose at positions equivalent to the 3- and 4-positions of D-galactose, was a very strong inhibitor, and D-lyxose, which in the furanose form also resembles D-galactose, was a much better inhibitor than expected. Structural comparisons prelude the pyranose forms of these sugars from being significant contributors to the inhibition, and inhibition at different temperatures (at which there are different furanose concentrations) strongly supported the conclusion that the furanose form is inhibitory. Studies with sugar derivatives that can only be in the furanose form also supported the conclusion. This is the first report of the inhibitory effect of furanose on beta-galactosidase. Lactones were also inhibitory. Every lactone tested was much more inhibitory than was its parent sugar. D-Galactonolactone was especially good. Experiments indicated that it was D-galactono-1,5-lactone rather than D-galactono-1,4-lactone which was inhibitory. Inhibition of beta-galactosidases from mammalian sources by lactones has been reported previously, but this is the first report of the effect of beta-galactosidase from E. coli. Since furanoses in the envelope form are analogous (in some ways) to half-chair or sofa conformations and since lactones with six-membered rings probably have half-chair or sofa conformations, the results indicate that beta-galactosidase probably destabilizes its substrate into a planar conformation of some type and that the galactose in the transition state may, therefore, also be quite planar.(ABSTRACT TRUNCATED AT 250 WORDS)
33 citations
TL;DR: In this paper, the Raman and i.r.d. spectra in the CH and CD-stretching region of D -glucose and five selectively deuterated derivatives in the solid state have been recorded.
28 citations
TL;DR: Evidence is presented that indicates that the shifts of these carbonyl carbon resonances depend on long-range interactions with other peracetylated pyranose monomers resulting from folding of the oligosaccharide chain.
28 citations
TL;DR: The idea that the amino acid residues near the glycosylated Thr influence orientation of the sugar moiety with respect to the peptides backbone and in turn possibly hinder peptide backbone flexibility has interesting implications in the conformational as well as the biological role of O‐glycoproteins.
Abstract: An 1H-nmr study of 2-acetamido-2-deoxy-3,4,6-tri-O-acetyl-D-galactopyranose (AcGalNAc) glycosylated Thr-containing tripeptides in Me2SO-d6 solution reveals two mutually exclusive intramolecular hydrogen bonds. In Z-Thr(AcGalNAc)-Ala-Ala-OMe, there is an intramolecular hydrogen bond between the Thr amide proton and the sugar N-acetyl carbonyl oxygen. The strength of this hydrogen bond will be dependent on the amino acid residues on the Thr C terminal side to some undetermined distance. In Ac-Thr(AcGalNAc)-Ala-Ala-OMe, a different intramolecular hydrogen bond between the sugar N-acetyl amide proton and the Thr carbonyl oxygen exists. The choice of hydrogen bonds seems dependent on the bulkiness of the residues on the Thr N terminal side. The consequence of such strong hydrogen bonds is a clearly defined orientation of the sugar moiety with respect to the peptide backbone. In the former, the plane of the sugar pyranose ring is roughly oriented perpendicularly to the peptide backbone. The latter orientation is where the plane of the sugar ring is roughly in line with the peptide backbone. In both orientations, the sugar moiety can increase the shielding of the neighboring amino acid residues from the solvent. The idea that the amino acid residues near the glycosylated Thr influence orientation of the sugar moiety with respect to the peptide backbone and in turn possibly hinder peptide backbone flexibility has interesting implications in the conformational as well as the biological role of O-glycoproteins.
24 citations
TL;DR: The first synthesis of 1,3-anhydro-2,4-di-Obenzyl-β- l -rhamnopyranose was reported in this paper.
15 citations
13 citations
TL;DR: In this article, the absolute configurations of open-chain vic-diols of the threo-configuration and of vicinal primary-secondary diols can be determined with small amounts of substance.
13 citations
TL;DR: In this paper, the pyranose ring was used as the tetrahydrocoumalate skeleton to synthesize methyl 2,3-anhydro-α-D-lyxopyranoside by cyclopentane annulation.
Abstract: 1-α-O-Methyl-loganin (1) was synthesised from methyl 2,3-anhydro-α-D-lyxopyranoside by cyclopentane annulation using the pyranose ring as the tetrahydrocoumalate skeleton.
TL;DR: In this article, a non-aqueous solution of bromine, iodine or selenophenyl with photolytically generated stannyl radicals from appropriately substituted pyranose derivatives and their e.r.s. spectra are recorded in the temperature range from −30 to 70 °C.
Abstract: Carbohydrate free radicals are generated in non-aqueous solution by abstraction of bromine, iodine or selenophenyl with photolytically generated stannyl radicals from appropriately substituted pyranose derivatives and their e.s.r. spectra are recorded in the temperature range from –30 to 70 °C. From the hyperfine splitting parameters the preferred conformations of these sugar radicals are derived. The findings are compared with results from investigations in aqueous solution and an attempt is made to identify the factors which determine the conformations. From the α-13C coupling constant of the tetra-acetylglucosyl radical it is concluded that pyranosyl radicals are of the π-type. A novel 1,2-migration of an acetoxy group in tetra-acetylgalactosyl radical is reported. The mechanism of interaction of nitrosugars and related compounds with tin radicals is discussed.
TL;DR: The crystal structures of four glycopyranosylcyanides derived from β-glucose, β-d -mannose, α-d-ribose, and α- d -idose were resolved by X-ray diffraction using direct methods.
TL;DR: Deoxy hydroxyamino sugars represent a potentially useful series of sugar analogs owing mainly to the fact that they oxidize spontaneously to nitroxide free radicals to give spin-labeled sugar derivatives whose structure is very close to that of the parent sugar as mentioned in this paper.
TL;DR: In this paper, a spontaneous intramolecular cyclization of the intermediate epoxides due to the free hydroxy group present in the starting enol ethers occurs, giving 1,2-trans-glycopyranosides from E-enol ether, although in the case of complex aglycones the cyclization is not entirely stereospecific.
Abstract: Z- and E-Hydroxyenol ethers, obtained from aldopentoses by a Horner–Wittig reaction, have been epoxidized using m-chloroperbenzoic acid or t-butyl hydroperoxide. A spontaneous intramolecular cyclization of the intermediate epoxides due to the free hydroxy group present in the starting enol ethers occurs, giving 1,2-trans-glycopyranosides from E-enol ethers. From Z-enol ethers, 1,2-cis-glycopyranosides are obtained, although in the case of complex aglycones the cyclization is not entirely stereospecific. The stereochemical course of both the epoxidation reaction and the pyranose ring formation from the intermediate epoxides is discussed.
TL;DR: Using comparative ion-exchange chromatography on Dowex 1X4, the product of dephosphorylation of fructose 2, 6-bisphosphate with purified yeast fructose-2,6-bisPhosphate 6-phosphohydrolase, was shown to be identical to the furanose form ofructose 2-ph phosphate prepared by chemical synthesis according to Pontis and Fischer.
Abstract: Using comparative ion-exchange chromatography on Dowex 1X4, the product of dephosphorylation of fructose 2,6-bisphosphate with purified yeast fructose-2,6-bisphosphate 6-phosphohydrolase, was shown to be identical to the furanose form of fructose 2-phosphate prepared by chemical synthesis according to Pontis and Fischer [Biochem. J. 89, 452–459 (1963)]. As expected for the furanose form of fructose 2-phosphate, the enzymatically formed product consums 1 mol periodate/mol fructose 2-phosphate, whereas the chemically synthesized pyranose form consumes 2 mol periodate/mol. In addition, it is shown that the enzymatic product behaves identically to the furanose, not the pyranose, form of fructose 2-phosphate in hydrolysis of the ester bond at pH 4 and 37°C, as described previously for the chemically synthesized compounds [Pontis and Fischer (1963) vide supra].
TL;DR: In this article, the thermal stability of reduced (4-O-methyl-D-glucurono)-D-xylan and nine methylglycosides related to this polysacharide were studied by dynamic and isothermal thermogravimetry.
Abstract: Reduced (4-O-methyl-D-glucurono)-D-xylan and nine methylglycosides related to this polysacharide were studied by dynamic and isothermal thermogravimetry. It could be stated from the results that the thermal stability of saccharides is increasing with increasing number of pyranose units. The models related to (4-O-methyl-D-glucurono)-D-xylan are more thermally stable than the corresponding hexoglycanic models. Rates of gasification of models containing uronic acid methylesters are higher than those of neutral methylglycosides. The rate of polysaccharide gasification was the highest one from all models studied. The supramolecular structure of polysaccharide is dramatically influencing the course of thermal degradation.
TL;DR: In this article, the major products from 5-thio-D-glucose and allosides are 2,3 : 4,6-di-O-isopropylidene-5-S-methyl-5 thio-d-aldehydo compounds.
Abstract: 5-Thio-D-glucose (9) reacts with acetone in the presence of an acid catalyst to give 1,2-O-5,6-S,O-di-isopropylidene-5-thio-α-D-glucofuranose (10). 5-Thio-D-altrose (37) similarly gives a 1,2 : 5,6-diacetal (39) but 5-thio-D-allose (27) affords 2,3-O-5,6-S,O-di-isopropylidene-5-thio-β-D-allofuranose (28). Under kinetic conditions, using 2,2-dimethoxypropane, the major products from 5-thio-D-glucose (9) and 5-thio-D-allose (27) are 2,3 : 4,6-di-O-isopropylidene-5-thin-D-gluco- and allopyranoses (11a) and (32), even though the former possesses a trans-fused dioxolane ring. 1,2 : 4,6-Di-O-isopropylidene-5-thio-α-D-glucopyranose (14), which is also produced in the former reaction, has been synthesised by an alternative route. 2,2-Dimethoxypropane and acetone react with methyl 5-thio-α- or β-D-glucopyranosides (3) or the related methyl 5-thio-α- or β-D-allopyranosides (25), to give the 2,3 : 4,6-diacetals (5) and (26) respectively. With acetone alone, the glucosides (3) give mainly the 4,6-monoacetals (4) together with smaller amounts of the 2,3 : 4,6- diacetals (5); the allosides (25) give complex mixtures and methyl 5-thio-α-D-altropyranoside (40) gives first the 4,6-acetal (41) which then isomerises into the 3,4-acetal (42). Methylation of either of the pyranose 2,3 : 4,6-diacetals (11a) or (32) leads to the corresponding 2,3 : 4,6-di-O-isopropylidene-5-S-methyl-5-thio-aldehydo compounds (44) and (45), respectively.
TL;DR: In this article, 13 N-(1-deoxy-d -fructos-1-yl)-N-nitroso- l -amino acids were prepared, in 83-95% yield, by nitrosation of the corresponding fructos with sodium nitrite in water-hydrochloric acid, at pH 3.
TL;DR: In this article, the furanose and pyranose ring transformations of glucose, arabinose and galactose in dimethyl sulfoxide solvent have been obtained by the combined technique of methylation, gas-liquid chromatography and mass spectrometry.
TL;DR: In this article, the major products from 5-thio-D-glucose and allosides are 2,3 : 4,6-di-O-isopropylidene-5-S-methyl-5 thio-d-aldehydo compounds.
Abstract: 5-Thio-D-glucose (9) reacts with acetone in the presence of an acid catalyst to give 1,2-O-5,6-S,O-di-isopropylidene-5-thio-α-D-glucofuranose (10). 5-Thio-D-altrose (37) similarly gives a 1,2 : 5,6-diacetal (39) but 5-thio-D-allose (27) affords 2,3-O-5,6-S,O-di-isopropylidene-5-thio-β-D-allofuranose (28). Under kinetic conditions, using 2,2-dimethoxypropane, the major products from 5-thio-D-glucose (9) and 5-thio-D-allose (27) are 2,3 : 4,6-di-O-isopropylidene-5-thin-D-gluco- and allopyranoses (11a) and (32), even though the former possesses a trans-fused dioxolane ring. 1,2 : 4,6-Di-O-isopropylidene-5-thio-α-D-glucopyranose (14), which is also produced in the former reaction, has been synthesised by an alternative route. 2,2-Dimethoxypropane and acetone react with methyl 5-thio-α- or β-D-glucopyranosides (3) or the related methyl 5-thio-α- or β-D-allopyranosides (25), to give the 2,3 : 4,6-diacetals (5) and (26) respectively. With acetone alone, the glucosides (3) give mainly the 4,6-monoacetals (4) together with smaller amounts of the 2,3 : 4,6- diacetals (5); the allosides (25) give complex mixtures and methyl 5-thio-α-D-altropyranoside (40) gives first the 4,6-acetal (41) which then isomerises into the 3,4-acetal (42). Methylation of either of the pyranose 2,3 : 4,6-diacetals (11a) or (32) leads to the corresponding 2,3 : 4,6-di-O-isopropylidene-5-S-methyl-5-thio-aldehydo compounds (44) and (45), respectively.
TL;DR: The crystal structure of C 19 H 36 NO 9 PS 2 (M r 517.65) was determined by direct methods and refined to R = 0.052 for 4074 independent reflections as mentioned in this paper.
01 Jan 1987
TL;DR: In this article, the negative charge is delocalized in the system formed by the two carbonyl groups at C4 and C6 and the carbon atom C5 of the barbituric ring.
Abstract: C10H15N3OT.3H20 , Mr= 343.3, monoclinic, P21, a = 10.883 (3), b = 12.497 (20), c = 10.553 (4) A, t= 91.05 (3) °, V= 1435 (2) A 3, Z=4, D m=1.57(2), D x=l.589Mgm -3, MoK~ 2= 0.7107/~, /t = 0.13 mm -~, F(000) = 728, T= 300 K, R = 0.064 for 2692 observed independent reflexions. The compound presents a zwitterionic structure in which the negative charge is delocalized in the system formed by the two carbonyl groups at C4 and C6 and the carbon atom C5 of the barbituric ring. In the two independent molecules in the asymmetric unit the pyranose ring adopts a 4C 1 conformation and the dihedral angles between the pyranose and barbituric
TL;DR: The cleavage of the C-H bond is accompanied by the decomposition of the pyranose ring as discussed by the authors, and the action of radiation on starch leads predominantly to the formation of terminal macroradicals with localization of the unpaired electron at C1 and C4.
Abstract: 1.
The action of radiation on starch leads predominantly to the formation of terminal macroradicals with localization of the unpaired electron at C1 and C4.
2.
The cleavage of the C-H bond is accompanied by the decomposition of the pyranose ring.
TL;DR: The first synthesis of 1,3-anhydro-2,4-di-Obenzyl-β- l -rhamnopyranose was reported in this article.
Abstract: The synthesis of 1,3-anhydro-2,4-di-O-benzyl- and 1,3-anhydro-2,4-di-O-(p-bromobenzyl)-β- l -rhamnopyranose was achieved via 8 steps, with l -rhamnose as the starting material. The key intermediates for the synthesis were 3-O-acetyl-2,4-di-O-benzyl- and 3-O-acetyl-2,4-di-O-(p-bromobenzyl)-α- l -rhamnopyranosyl chloride that were transformable into the target compounds by ring closure with potassium tert-butoxide. Vicinal and long-range proton-proton coupling-constants suggested that the conformation of the 1,3-anhydro sugar ethers is essentially B2,5( l ) with some lowering of the boat head at C-5 for the pyranose ring, and a chair for the 1,3-dioxane ring.
TL;DR: In this article, an IR-spectroscopic method for determining the degree of deuteration of the hydroxy groups of pectin substances (PSs) is described.
Abstract: An apparatus for the deuteration of solid samples and for recording their IR spectra in a current of D2O vapor, and an IR-spectroscopic method of determining the degree of deuteration (q) of the hydroxy groups of pectin substances (PSs) are described. It has been established that there are no zones of structurally different nature in films of derivatives of PSs at the carboxy group. The rate of deuterium-exchange of the water of hydration of PSs is higher than for the hydroxy groups of the pyranose rings. The rate of deuterium exchange depends on the density of packing of the polymer chains of the pectin derivatives.
TL;DR: In this paper, the 1-(beta-D-Ribopyranosyl)hexahydropyrimidin-2-one (7) was synthesized and used in conjunction with its furanose isomer 6 as a model compound for more extensive 1H and 13C NMR, mass spectral, and kinetic studies of this isomerization.
Abstract: Tetrahydrouridine (THU, 2) and other fully reduced cyclic urea ribofuranosyl nucleosides undergo a rapid, acid-catalyzed isomerization to their more stable ribopyranosyl form. This isomerization is characterized by a change in spectral properties and by a greater than 10-fold decrease in potency for those nucleosides that act as potent inhibitors of cytidine deaminase in their ribofuranose form. 1-(beta-D-Ribopyranosyl)hexahydropyrimidin-2-one (7) was synthesized and used in conjunction with its furanose isomer 6 as a model compound for more extensive 1H and 13C NMR, mass spectral, and kinetic studies of this isomerization. The 0.4 delta upfield shift and 4-Hz increase in the J1',2' coupling constant for the pyranose anomeric proton in the 1H NMR spectrum is indicative of a pyranose beta-CI conformation in which the aglycon and C-2' and C-4' hydroxyls are equatorial. The mass spectra of trimethylsilylated pyranose nucleosides also show a characteristic large shift in the m/z 204-217 abundance and the appearance of two new rearrangement ions at M-133 and M-206. For furanose 6 the rate of isomerization is pH and temperature dependent with pyranose 7 predominating by a factor of 6-9 equilibrium. At pH 1 and 37 degrees C, furanose 6 has an initial half-life of less than 12 min. Accordingly, this isomerization may explain the observed lack of enhanced ara-C levels in studies evaluating the oral administration of an ara-C and THU combination to species with an acidic stomach content.
TL;DR: Oxygens present in ethers, esters, and pyranose rings participate efficiently in electrophilic reactions at remote centres leading to five-and six-membered heterocycles.
Abstract: Oxygens present in ethers, esters, and pyranose rings participate efficiently in electrophilic reactions at remote centres leading to five- and six-membered heterocycles.
TL;DR: In this article, the trityl group in methyl-2,3-di-O-acetyl-4-Otrityl-β-D-xylopyranoside for triarylmethyl groups containing electron-donor substituents in the aromatic ring does not appreciably affect the stereochemistry of the glycosylation.
Abstract: 1.
4-O-(p-Tolyldiphenylmethyl)-, 4-O-(di-p-tolylphenylmethyl) and 4-O-(p-anisyldiphenyl-raethyl) derivatives of methyl-2,3,-di-O-acetyl-β-D-xylopyranoside were synthesized.
2.
A study of the reaction of the above compounds with 3,4-di-O-acetyl-1,2-O-[1-(endo-cyano)ethylidene]-α-D-xylopyranose showed that exchange of the trityl group in methyl-2,3-di-O-acetyl-4-O-trityl-β-D-xylopyranoside for triarylmethyl groups containing electron-donor substituents in the aromatic ring does not appreciably affect the stereochemistry of the glycosylation, but can lead to decrease in the yield of the disaccharides.
3.
A trans-triarylmethylation reaction was discovered with the reaction of methyl-2,3-di-O-acetyl-4-O-(p-anisyldiphenylmethyl)-β-D-xylopyranoside with triphenylmethylium perchlorate as an example.
TL;DR: In this paper, a spontaneous intramolecular cyclization of the intermediate epoxides due to the free hydroxy group present in the starting enol ethers occurs, giving 1,2-trans-glycopyranosides from E-enol ether, although in the case of complex aglycones the cyclization is not entirely stereospecific.
Abstract: Z- and E-Hydroxyenol ethers, obtained from aldopentoses by a Horner–Wittig reaction, have been epoxidized using m-chloroperbenzoic acid or t-butyl hydroperoxide. A spontaneous intramolecular cyclization of the intermediate epoxides due to the free hydroxy group present in the starting enol ethers occurs, giving 1,2-trans-glycopyranosides from E-enol ethers. From Z-enol ethers, 1,2-cis-glycopyranosides are obtained, although in the case of complex aglycones the cyclization is not entirely stereospecific. The stereochemical course of both the epoxidation reaction and the pyranose ring formation from the intermediate epoxides is discussed.