Showing papers on "Pyranose published in 1986"

Use of synthetic glycoconjugates containing the Mycobacterium leprae specific and immunodominant epitope of phenolic glycolipid I in the serology of leprosy.

Abstract: The high specificity of phenolic glycolipid I (PG-I) in the identifying individuals with leprosy appears to be attributable to the species-specific trisaccharide region of the molecule. Synthetic glycoconjugates were produced by coupling the corresponding terminal mono- or disaccharide to bovine serum albumin by reductive amination. Conjugates which contained only the terminal sugar maintained in its pyranose form, the terminal disaccharide with only the terminal sugar in its pyranose form and the terminal disaccharide with both the 3,6,di-o-Me-glucose and 2,3,di-o-Me-rhamnose sugars in their pyranose forms, were all highly active in the enzyme-linked immunosorbent assay (ELISA) and showed good concordance with native PG-1 in analysis of sera from leprosy patients. The antibody levels to the glycoconjugates in tuberculosis patients and patients with other mycobacterial infections were not significantly different from the levels in normal healthy control subjects. A few of the leprosy sera showed much stronger binding to conjugates which contained the disaccharide with both sugars in the pyranose form than to conjugates with only the terminal sugar in its pyranose form. Therefore a synthetic conjugate which contains the intact disaccharide region of PG-I may provide the most sensitive antigen for the large scale serodiagnosis of leprosy.

Furanose-pyranose isomerization of reduced pyrimidine and cyclic urea ribosides.

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.

Complete structural analysis of globoseries glycolipids by two-dimensional nuclear magnetic resonance.

Abstract: Combined two-dimensional proton nuclear magnetic resonance allowed the determination of complete oligosaccharide structures of glycolipids belonging to the globo series, without any other analytical methods. Although a chemical modification by peracetylation was required for the above purpose, the derivatization permitted facile assignment of the pyranose ring proton resonances of the oligosaccharide moiety. Two-dimensional chemical-shift-correlated spectroscopy of the acetylated glycolipid enabled us to elucidate the glycosidic positions from the chemical shifts of the protons at the substituted sites. The monosaccharide species were also identified from the characteristic splitting patterns of the methine protons on individual pyranose rings. The sequence of the monosaccharides was inferred from the interresidue connectivity across glycosidic linkages shown by two-dimensional nuclear Overhauser effect spectroscopy, which also gave intraresidue interaction on the pyranose rings. The linkage sites of long oligosaccharide chains having more than five monosaccharides, such as globopentaosylceramide, were analyzed by two-dimensional J-relayed coherence transfer, which yielded 1,3 interactions along with 1,2 interactions.

Remote participation in electrophilic reactions of ‘protected’ polyols

Abstract: Oxygens present in ethers, esters, and pyranose rings participate efficiently in electrophilic reactions at remote centres leading to five- and six-membered heterocycles.

The Deoxygenation of Some Carbohydrate Diols Via the Derived Cyclic Thiocarbonate

Abstract: The treatment of methyl 2,6-di-O-methyl-3,4-O-thiocarbonyl-β-D-galactoside with methyl iodide gives mainly the 3-deoxy-3-iodo-D-guloside , whereas the α- anomer of the above and methyl 2-O-methyl-3,4- O- thiocarbonyl-β-L-arabinoside give mainly the 4-deoxy-4-iodo-D- glycosides. An explanation is given for these and some previously reported results. As well, two of the above cyclic thiocarbonates (β-D-galacto and β-L- arabino), together with two cyclic thiocarbonates derived from methyl α-D- mannopyranoside, when treated with tributyltin hydride, gave mixtures (nearly 1:1) of products resulting from deoxygenation . Single-crystal X-ray diffraction structure determination of the β-D- galacto and the β-L- arabino cyclic thiocarbonates showed both pyranose rings to be in the 4C1 conformation.

2-substituted arabinopyranosyl nucleosides and nucleotides

Abstract: Novel arabinopyranosyl nucleoside derivatives having the heterocyclic moiety and fluorine at the 2' position of the sugar ring (pyranose configuration), which have antitumor, antiviral and antimicrobial properties, are prepared by condensation of a pyrimidine, purine or 1,3-oxazine base with an acylated 2-deoxy-2,2-difluoro-D-arabinopyranoside and/or acylated 2-deoxy-2-bromo-2-fluoro-D-arabinopyranoside.

Alternative synthesis and regioselective coupling of 1,6‐anhydro‐2‐azido‐ and ‐2‐phthalimido‐2‐deoxy‐β‐D‐galactopyranose

Abstract: Easily accessible 1,6-anhydro-3,4-isopropylidene-β-D-galactopyranose has been converted in four steps (i.e., oxidation, reduction, triflation and Walden inversion with lithium azide or potassium phthalimide) into 1,6-anhydro-2-azido- or -2-phthalimido-2-deoxy-3,4-O-isopropylidene-β-D-galacto- pyranose. The 2-azido derivative, obtained after acidolysis of the isopropylidene group, could be coupled regioselectively at the hydroxyl group at C-4 with either 1,3,4,6-tetra-O-acetyl-2-phthalimido-2-deoxy-β-D- glucopyranose or 3,4,6-tri-O-acetyl-2-phthalimido-2-deoxy-α-D-glucopyranosyl bromide in the presence of the soluble catalyst, trimethylsilyl trifluoromethanesulphonate, or the insoluble catalyst, silver silicate.

β-Glucocerebrosidase: Affinity Purification and Characterization of its Active Site with N-Alkyl Derivatives of 1-Deoxynojirimycin

Abstract: An essential feature of the catalytic site of practically all β-glucosidases is a carboxylate group in close proximity to the glucosyl C-1 of the bound substrate. It participates in the bond breaking step by stabilizing a positive charge developing at this carbon atom and/or by forming an α-glucosyl enzyme intermediate which subsequently hydrolyses to β-glucose. The presence and orientation with respect to the bound substrate of this carboxylate is revealed by the covalent inhibition of these enzymes by epoxides related to glucose and by their strong non-covalent inhibition by glucose derivatives with a basic group at C-1 which is up to 103-times better than by the corresponding non-basic derivativesl. We have used the latter property to develop an affinity purification for β-glucocerebrosidase from calf spleen and to explore the aglycon part of its active site with N-alkyl derivatives of 1-deoxynojirimycin (dNM, 1,5-dideoxy-1,5-imino-D-glucitol), a basic analogue of D-glucose where the pyranose oxygen has been replaced by an NH-group.

Novel oligosaccharide and production thereof

Abstract: PURPOSE: To obtain an oligosaccharide useful as a proliferation promoting factor for bifidus bacteria, by treating a mixture of lactose(-containing component) and a component selected from starch, etc., with a specific enzyme. CONSTITUTION: A mixture of lactose(-containing component) and a component selected from starch, starch syrup, etc., is added with 0.1W200 unit/ml of α- glucosidase active to transfer starch to lactose and is made to react at 3W7pH and 20W60°C. The reaction liquid is treated to obtain 0-α- glucopyranosyl-(1→3)-0-β-D-galactopyranosyl-(1→4)-D-glucose of formula having the following physical and chemical properties. Molecular weight, 504; constituent sugar, 2mol of glucose and 1mol of galactose; bonding type of constituent sugars, 1-site C forms lactose by forming β-(1→4) bond with glucose, 5-site C forms a pyranose ring, 3-site C bonds with glucose, glucose forms an α-(1→3) bond with galactose in lactose; solubility, easily soluble in water and insoluble in acetone, etc.; color reaction positive to NaOH reaction and negative to ninhydrin reaction; color, white; nature, neutral; etc. COPYRIGHT: (C)1987,JPO&Japio

Two Complementary Methods for Introduction of gem-Dimethyl Group in Hexopyranoside Ring.

Abstract: Hexopyranosides having a gem-dimethyl group in the pyranose ring were synthesized By reductive cleavage of spiro-cyclopropane derivatives and By addition of methyl cuprates to methyl-branched enolone derivatives.

Mass spectrometry of pennogenin glycosides

Abstract: The electron-impact mass spectra of five unesterified pennogenin glycosides, which contain the M+ or (M - H2O)+ peaks, have been obtained. The characteristic features of the fragmentation of these compounds have been studied. In addition to ions characterizing the successive elimination of carbohydrate units, fragments have been detected which show the breakdown of the terminal pyranose ring. Five new directions of the fragmentation of the spirostanol skeleton due to the presence of an OH group at C-17 have been found.

The Deoxygenation of Some Carbohydrate Diols via the Derived Cyclic Thiocarbonate.

Abstract: The treatment of methyl 2,6-di-O-methyl-3,4-O-thiocarbonyl-β-D-galactoside with methyl iodide gives mainly the 3-deoxy-3-iodo-D-guloside , whereas the α- anomer of the above and methyl 2-O-methyl-3,4- O- thiocarbonyl-β-L-arabinoside give mainly the 4-deoxy-4-iodo-D- glycosides. An explanation is given for these and some previously reported results. As well, two of the above cyclic thiocarbonates (β-D-galacto and β-L- arabino), together with two cyclic thiocarbonates derived from methyl α-D- mannopyranoside, when treated with tributyltin hydride, gave mixtures (nearly 1:1) of products resulting from deoxygenation . Single-crystal X-ray diffraction structure determination of the β-D- galacto and the β-L- arabino cyclic thiocarbonates showed both pyranose rings to be in the 4C1 conformation.