- Photoinitiated glycosylation at 350 nm
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A method for photochemical activation of glycosyl donors is presented. Selenoglycosides were activated by single-electron transfer using a photooxidant, N-methylquinolinium hexafluorophosphate, as photosensitizer and a toluene cosolvent as cosensitizer under irradiation at 350 nm. In this way we were able to synthesize glycosides including (1→6)-linked disaccharides. Benzyl ethers and benzoate esters were compatible with these conditions, allowing potentially synthetically useful transformations. The major by-products were due to hydrolysis; the reactions required the presence of oxygen and were run in air.
- Cumpstey, Ian,Crich, David
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experimental part
p. 469 - 485
(2012/06/15)
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- An efficient method for the preparation of glycosides with a free C-2 hydroxyl group from thioglycosides
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A new and efficient method to produce glycosides with a free C-2 hydroxyl group through 1,2-acyl group migration which occurs during the hydrolysis of 4,6-benzylidene protected thioglycosides has been developed. The acyl transfer products allow for further elaboration.
- Yu, Hai,Ensley, Harry E.
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p. 9363 - 9366
(2007/10/03)
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- Carbohydrate Homologation by the Use of 2-(Trimethylsilyl)thiazole. Preparative Scale Synthesis of Rare Sugars: L-Gulose, L-Idose, and the Disaccharide Subunit of Bleomycin A2
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The well established one-carbon homologation method of protected monosaccharides employing 2-(trimethylsilyl)thiazole (2-TST) as a formyl anion equivalent has been used for high yield and multigram scale synthesis of the title rare hexoses from L-xylose. Thus, L-gulose has been obtained by stereoselective anti-addition of 2-TST to aldehydo-L-xylose diacetonide followed by thiazole to formyl conversion of the resulting alcohol. The inversion of configuration at C-1 of this alcohol by an oxidation - reduction sequence prior to the aldehyde releasing from thiazole led to L-idose. The same alcohol was readily elaborated into 1,3,4,6-tetra-O-acetyl-L-gulopyranose whose highly stereoselective glycosidation coupling with 3-O-carbamoyl-2,4,6-tri-O-acetyl-α-D-mannosyl diethyl phosphate afforded the same peracetylated disaccharide subunit employed by Boger and Honda in the total synthesis of the antibiotic bleomycin A2.
- Dondoni, Alessandro,Marra, Alberto,Massi, Alessandro
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p. 6261 - 6267
(2007/10/03)
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- Glycosylation of triterpene alcohols and acids of the lupane and A-secolupane series
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A series of 3- and 28-glucosides and glucosyl esters of betulinic acid (1a), 28-hydroxy-3,4-secolupa-4(23),20(29)-dien-3-oic acid (22a), dimethyl ester of 28-hydroxy-2,3-secolup-20(29)-en-2,3-dioic acid (43a), their 20(29)-dihydro derivatives (1b, 22b, 43b) and several other triterpenes of the lupane (12a, 12b) and 3,4-secolupane series (18a, 18b, 32a) has been prepared by reaction of tetra-O-acetyl-α-D-glucopyranosyl bromide in acetonitrile in the presence of mercury(II) cyanide and subsequent deacetylation of the obtained tetra-O-acetyl-β-D-glucopyranosyl derivatives. In several cases attempted glucosylation in the presence of silver silicate afforded predominantly the corresponding 1,2-orthoacetates of α-D-glucopyranose.
- Klinotova, Eva,Krecek, Vaclav,Klinot, Jiri,Endova, Magdalena,Eisenreichova, Jana,Budesinsky, Milos,Sticha, Martin
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p. 1776 - 1798
(2007/10/03)
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- An electrochemical synthesis of methyl α-isomaltoside
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A novel approach has been developed for the synthesis of methyl α-isomaltoside (10), comprising, as the first step, electrochemical conversion of the hydroxyl groups of methyl α-D-glucopyranoside into the corresponding anions.The anions subsequently react with tetra-O-acetyl-α-D-glucopyranosyl bromide to give methyl 2',3',4',6'-tetra-O-acetyl-α-isomaltoside (8) as the main product.O-deacetylation of which affords 10.The glycosidation proceeds under complete stereochemical control.Keywords: Isomaltoside, methyl α-; Disaccharides; Electrochemical synthesis; Structure
- Hamann, Carl Heinz,Polligkeit, Herbert,Wolf, Peter,Smiatacz, Zygfryd
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- Syntheses and 1H- and 13C-Nuclear Magnetic Resonance Spectra of All Positional Isomers of Tetra-O-acetyl-D-glucopyranoses, and Their Monobenzyl and Monotrityl Derivatives
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All the isomers of the tetra-O-acetyl-D-glucopyranoses, and their monobenzyl and monotrityl derivatives were synthesized and systematic 1H- and 13C-nuclear magnetic resonance (1H- and 13C-NMR) studies were carried out.Complete assignments of the 1H- and 13C-NMR signals were achieved by 1H- and 13C-decoupling techniques and by the use of a shift reagent and changes of solvents.Moreover, when necessary, 1H- and 13C-shift-correlated 2D NMR spectroscopy at higher frequency (Bruker AM 400) was applied.The shifts on deacetylation, benzylation, and tritylation were estimated on the basis of the 1H- and 13C-chemical shifts of these compounds, and the effects of deacetylation and benzyl- or trityl-substitution are discussed.Keywords - tetra-O-acetyl-D-glucopyranose; monobenzyl tetra-O-acetyl-D-glucopyranose; monotrityl tetra-O-acetyl-D-glucopyranose; 1H-NMR; 13C-NMR; deacetylation shift; benzylation shift; tritylation shift
- Utamura, Toshiko,Kuromatsu, Keiko,Suwa, Kiyoko,Koizumi, Kyoko,Shingu, Tetsuro
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p. 2341 - 2353
(2007/10/02)
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- A COMPARISON OF BIS(TRIBUTYLTIN) OXIDE, POTASSIUM CYANIDE, AND POTASSIUM HYDROXIDE AS REAGENTS FOR THE REGIOSELECTIVE 1-O-DEACETYLATION OF FULLY ACETYLATED SUGARS
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Treatments of fully acetylated sugars with bis(tributyltin) oxide in toluene at reflux, and with potassium cyanide or potassium hydroxide, or both, in mixtures of tetrahydrofuran and 2-propanol were found to be effective for regioselective 1-O-deacetylation of fully acetylated sugars.
- Watanabe, Kazuko,Itoh, Kiyotaka,Araki, Younosuke,Ishido, Yoshiharu
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p. 165 - 176
(2007/10/02)
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