- Preparation of sugar derivatives using the amalgam process
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Methyl α-D-glucopyranoside dissolved in N,N-dimethylformamide was benzylated with benzylbromide using sodium amalgam and grains of an electrocatalyst for the generation of intermediate sugar anions. The obtained substitution pattern is comparable to the p
- Hamann, Carl Heinz,Roepke, Thorsten
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- Aqueous Glycosylation of Unprotected Sucrose Employing Glycosyl Fluorides in the Presence of Calcium Ion and Trimethylamine
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We report a synthetic glycosylation reaction between sucrosyl acceptors and glycosyl fluoride donors to yield the derived trisaccharides. This reaction proceeds at room temperature in an aqueous solvent mixture. Calcium salts and a tertiary amine base promote the reaction with high site-selectivity for either the 3′-position or 1′-position of the fructofuranoside unit. Because nonenzymatic aqueous oligosaccharide syntheses are underdeveloped, mechanistic studies were carried out in order to identify the origin of the selectivity, which we hypothesized was related to the structure of the hydroxyl group array in sucrose. The solution conformation of various monodeoxysucrose analogs revealed the co-operative nature of the hydroxyl groups in mediating both this aqueous glycosyl bond-forming reaction and the site-selectivity at the same time.
- Pelletier, Guillaume,Zwicker, Aaron,Allen, C. Liana,Schepartz, Alanna,Miller, Scott J.
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supporting information
p. 3175 - 3182
(2016/03/19)
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- Chemical Synthesis of Disaccharides which are Partial Structures of the Glycosaminoglycan Heparan Sulfate
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A specific tetradecasaccharide sequence (oligo-H, 1) of the proteoglycan heparan sulfate has recently been identified as being responsible for binding and activation of the basic fibroplast growth factor (bFGF), a potent mitogen.We present here the first
- Davis, Nicola J.,Flitsch, Sabine L.
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p. 359 - 368
(2007/10/02)
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- Catalytic transfer hydrogenation of benzylic and styryl compounds with palladium/carbon and 2-propanol. Selective removal of O-benzyl groups from carbohydrate derivatives
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2-Propanol is shown to be an effective hydrogen donor, in the presence of palladium/carbon, for catalytic transfer hydrogenation reactions of benzylic and styryl compounds, e.g., for the quantitative conversion of cinnamyl alcohol into 3-phenylpropanol.In the reduction of derivatives of cinnamic acid, decarboxylation also occurs.During the latter reaction, the phenyl group appears to function as an anchoring group for the palladium atom, because derivatives of phenylpropanoic acid are decarboxylated more readily than are those of phenylacetic acid.In hydrogenolysis reactions, aryl alcohols undergo disproportionation whereas benzyl ethers, represented by O-benzyl and related derivatives of carbohydrates, are smoothly cleaved.Although 2-propanol is less reactive as a hydrogen donor than formic acid, it exhibits greater selectivity, as illustrated by relative rates of hydrogenolysis of O-benzyl and O-benzylidene substituents.The use of alumina-supported palladium is more effective than palladium/carbon for promoting stepwise removal of O-benzyl substituents, as shown by the preparation of methyl 2-O-benzyl- and -3-O-benzyl-α-D-glucopyranoside from the 2,3-di-O-benzyl derivative.A possible relationship between the orientation of O-benzyl groups and the chemical shift differences between the diastereotopic benzylic protons is decribed.
- Rao, Vanga S.,Perlin, Arthur S.
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p. 652 - 657
(2007/10/02)
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