- Scope of the DMC mediated glycosylation of unprotected sugars with phenols in aqueous solution
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Activation of reducing sugars in aqueous solution using 2-chloro-1,3-dimethylimidazolinium chloride (DMC) and triethylamine in the presence of para-nitrophenol allows direct stereoselective conversion to the corresponding 1,2-Trans para-nitrophenyl glycosides without the need for any protecting groups. The reaction is applicable to sulfated and phosphorylated sugars, but not to ketoses or uronic acids or their derivatives. When applied to other phenols the product yield was found to depend on the pKa of the added phenol, and the process was less widely applicable to 2-Acetamido sugars. For 2-Acetamido substrates an alternative procedure in which the glycosyl oxazoline was pre-formed, the reaction mixture freeze-dried, and the crude product then reacted with an added phenol in a polar aprotic solvent system with microwave irradiation proved to be a useful simplification.
- Fairbanks, Antony J.,Qiu, Xin
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p. 7355 - 7365
(2020/10/13)
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- A new look at acid catalyzed deacetylation of carbohydrates: A regioselective synthesis and reactivity of 2-O-acetyl aryl glycopyranosides
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In the present work we report that acetyl groups of per – acetylated aryl glycosides have different reactivity during the acidic deacetylation using HCl/EtOH in CHCl3, which leads to preferential deacetylation at O-3, O-4 and O-6. Thereby, the one-step preparation of 2-O-acetyl aryl glycosides with simple aglycon was accomplished for the first time. It was proved that the found reagent is to be general and unique for the preparation of series of 2-О-acetyl aryl glycosides. We have determined the influence of both carbohydrate moiety and the aglycon on the selectivity of deacetylation reaction by kinetic experiments. Using DFT/B3LYP/6-31G(d,p) and semi-empirical АМ1 methods we have found that the highest activation barrier is for 2-О-acetyl group. This completely explains the least reactivity of 2-О-acetyl group.
- Stepanova, Elena V.,Nagornaya, Marina O.,Filimonov, Victor D.,Valiev, Rashid R.,Belyanin, Maxim L.,Drozdova, Anna K.,Cherepanov, Victor N.
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- PHENOL GLYCOSIDES AND THEIR USE IN THE TREATMENT OF UROLITHIASIS
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The present invention relates to novel derivatives of polyphenol glycoside or polyalcohols of formula (1), wherein R1, R2, R3 is selected from the group consisting of H, OH, C(O)R4, C(0) OR4, 0 (Gly H3)n, wherein n = 0 1, 2, 3, and R4 is selected from the group consisting of H, alkyl, and Gly is a mono- or disaccharide residue. The present invention also relates to novel derivatives of glycoside polyphenols or polyalcohols, as pharmaceutical composition comprising a novel polyphenol glycoside or polyalcohols and the use of novel polyphenol glycoside or polyalcohols for the treatment of urolithiasis.
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Page/Page column 26; 27; 30; 31
(2017/01/26)
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- Aryl O- and S-galactosides and lactosides as specific inhibitors of human galectins-1 and -3: Role of electrostatic potential at O-3
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Phase transfer catalyzed reaction was used for the high yielding synthesis of aryl 1-thio-β-d-galacto- and lacto-pyranosides carrying a panel of substituents on the phenyl groups. Best galectin-1 inhibitors were simple p-nitrophenyl thiogalactoside 5a for
- Giguere, Denis,Sato, Sachiko,St-Pierre, Christian,Sirois, Suzanne,Roy, Rene
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p. 1668 - 1672
(2007/10/03)
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- Preparative Bioorganic Chemistry, XVI. Synthesis of 3,4'-Dihydroxypropiophenone 3-&β-D-Glucopyranoside, a Constituent of Betula platyphylla var. japonica, by Enzymatic Transglucosylation
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3,4'-Dihydroxypropiophenone 3-β-D-glucopyranoside (1a) has been synthesized, without having recourse to any protective group technology, by transglucosylation catalyzed by lactase from Kluyveromyces lactis. Key words: Antifeedant; Betula platyphylla; β-D-glucopyranoside; lactase; transglucosylation.
- Mori, Kenji,Qian, Zhao-Hui,Watanabe, Sadamoto
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p. 485 - 488
(2007/10/02)
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- STEREOSELECTIVE SYNTHESES OF O- AND S-NITROPHENYL GLYCOSIDES. PART III. SYNTHESES IN THE &α-D-GALACTOPYRANOSE AND &α-MALTOSE SERIES
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The action of p-nitrophenol penta-O-acetyl-β-D-galactopyranose in dichloromethane, in the presence of stannic tetrachloride gave p-nitrophenyl α-D-galactoside in fair yield.This technique failed when o-nitrophenol was used.Tetra-O-acetyl-β-D-galactopyranosyl and hepta-O-acetyl-β-maltosyl chlorides were converted to p- or o-nitrophenyl α-D-glycosides and p-nitrophenyl α-D-1-thioglycosides in good yield using hexamethylphosphoramide as a solvent and the sodium salt of the phenols as nucleophiles.The galactosides have been functionalized for further condensation at the C-4 position by selective benzoylation.
- Apparu, Maecel,Blanc-Muesser, Michele,Defaye, Jacques,Driguez, Hugues
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p. 314 - 320
(2007/10/02)
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- Alpha-galactosidase production
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A process for the production of α-galactosidase by culturing the mold Penicillium duponti in an aqueous medium containing at least one sugar with at least one αD-galactopyranosyl bond and collecting the mycelium thus obtained.
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