Topic
Pyranose
About: Pyranose is a research topic. Over the lifetime, 1619 publications have been published within this topic receiving 35348 citations. The topic is also known as: pyranoses & hexopyranose.
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TL;DR: The results suggest that the enhancement of transfection efficiency of Gal-6ACT was not due to the increase of receptor-mediated cellular uptake, and the enhanced gene transfer efficiency was not specific to the galactose modification.
36 citations
TL;DR: In this article, the authors described 1.1, 2.4, 5, and 6 pyranose as the precursors of D-Fructose and Perchloric acid, respectively.
Abstract: 1, 2:4,5-Di-O-isopropylidene-beta-D-fructopyranose
D-Fructose
1,2:4,5-Di-O-isopropylidene-D-erythro-2, 3-hexadiulo-2, 6-pyranose
Perchloric acid
Pyridinium chlorochromate
Keywords:
enantioselective ketones;
catalysts;
epoxidation;
waste disposal;
dioxiranes;
asymmetric synthesis;
fructose;
perchloric acid;
pyranose
36 citations
TL;DR: Comparison of log kcat values with spontaneous hydrolysis rates indicates that nucleophilic and non-covalent interactions accelerate C–N bond cleavage in the ES complex by a factor of 10, which indicates the presence of a negative charge in the El complex near C-1 on the α face of the pyranose ring.
Abstract: (1)α-Deuterium kinetic isotope effects on Vmax. for hydrolysis of both β-D-glucopyranosylpyridinium ions and aryl β-D-glucopyranosides are in the range kH/kD 1.08–1.14, indicating that bond-breaking limits the rate of hydrolysis of both sets of substrates. The variation of kcat with aglycone acidity, expressed by log kcat=A+βlgpKa, is governed by a βlg value of –0.96 ± 0.19 for the N-glycosides and –0.05 ± 0.05 for the O-glycosides. The latter, low value of |βlg| is evidence for extensive proton donation to the oxygen at the transition state, even for the departure of acidic aglycones. The dependence of rate on protonation of a group of pKa < 6 required by this idea is indeed observed. (2) Comparison of log kcat values with spontaneous hydrolysis rates indicates that nucleophilic and non-covalent interactions accelerate C–N bond cleavage in the ES complex by a factor of 10(8 + 0.3[pka]N) for glucosyl pyridinium salts where [pKa]N is the pKa of the pyridine. On the assumption that these interactions are similar for O-glucosides, proton donation to the aglycone oxygen atom can be estimated to contribute a rate-enhancement of 10(0.1 + 0.7[pKa]O), where [pKa]O is that of the free phenol. (3)D-Glucono-δ-lactone and 5-amino-5-deoxy-D-gluconolactam are bound 102.8 and 102.2 times, respectively, more tightly than β-D-glucopyranose, because of their analogy to a transition state in which α-deuterium kinetic isotope effects have shown the anomeric carbon atom to have substantial sp2 character. (4) Cationic inhibitors are bound 102.5–103.5 times more tightly than directly comparable neutral ones, if the positive charge resides on the equatorial substituent at C-1, but protonated 2-amino-2-deoxyglucose is bound no more tightly than glucose. This indicates the presence of a negative charge in the El complex near C-1 on the α face of the pyranose ring (an aspartate residue previously identified by covalent labelling) which is partly compensated by a positive charge near C-2.
36 citations
TL;DR: The versatile enantiopure cis-dihydrodiol metabolite 1, formed by bacterial metabolism of iodobenzene, has been used for the synthesis of the pyranose carbasugars (pseudosugars) and the relative and absolute configurations of compounds 2-5 were established by a combination of stereochemical correlation, X-ray crystallography and 1H-NMR spectroscopy.
Abstract: The versatile enantiopure cis-dihydrodiol metabolite 1, formed by bacterial metabolism of iodobenzene, has been used for the synthesis of the pyranose carbasugars (pseudosugars) carba-beta-D-altropyranose 2, carba-alpha-L-galactopyranose 3, carba-beta-D-idopyranose 4 and carba-beta-L-glucopyranose 5. Substitution of the iodine atom by a carbomethoxy group, stereoselective catalytic hydrogenation of an alpha,beta-unsaturated ester, and regioselective inversion of one or two allylic chiral centres are the key steps used in the synthesis of carbasugars 2-5. The relative and absolute configurations of compounds 2-5 were established by a combination of stereochemical correlation, X-ray crystallography and 1H-NMR spectroscopy.
36 citations
TL;DR: In the sialic acid aldolase-catalysed addition of pyruvate with D-arabinose leading to a mixture of 3-deoxy-D-manno-oct-2-ulosonic acid (KDO) and 4-epi-KDO, a high concentration of the acceptor D-Arabinose have been found to increase the percentage of KDO up to 83%.
Abstract: In the sialic acid aldolase-catalysed addition of pyruvate with D-arabinose leading to a mixture of 3-deoxy-D-manno-oct-2-ulosonic acid (KDO) and 4-epi-KDO (both in pyranose and furanose form), a high concentration of the acceptor D-arabinose have been found to increase the percentage of KDO up to 83%. KDO synthesis scaled up in the enzyme membrane reactor is reported. New condensation products obtained from L-xylose, L-allose, D-altrose and D-ribose as substrates are described as well. Kinetic parameters for the cleavage of KDO and 4-epi-KDO and the addition reaction between pyruvate and xylose and arabinose are given. Some apparent relation between enzyme stereoselectivity and conformation and stereochemistry at carbon C-3 of the substrate is discussed.
36 citations