- Glycosylation Enabled by Successive Rhodium(II) and Br?nsted Acid Catalysis
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Herein, we reported on a highly efficient glycosylation reaction comprising two chronological meticulously designed catalytic cycles: (1) rhodium-catalyzed formation of sulfonium ylide and (2) Br?nsted acid-catalyzed formation of sulfonium ion. This protocol highlighted an effective and robust tactic to prepare a glycosyl sulfonium ion from a glycosyl sulfonium ylide precursor amenable for glycosylation.
- Meng, Lingkui,Wu, Peng,Fang, Jing,Xiao, Ying,Xiao, Xiong,Tu, Guangsheng,Ma, Xiang,Teng, Shuang,Zeng, Jing,Wan, Qian
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supporting information
p. 11775 - 11780
(2019/08/20)
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- Synthesis, NMR, and Conformational Studies of some 1,2- and 1,3-Linked Disaccharides
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Eight 1,2- and 1,3-linked disaccharides have been synthesized in which the glycosidic linkages have different stereochemical environments. 1H and 13C NMR studies and conformational analysis, using the HSEA-approach, indicate a number of proton-oxygen and proton-proton interactions, resulting, inter alia, in downfield and upfield shifts of signals from protons involved in the glycosidic linkages and upfield shift of signals from carbons which have their protons in γ-gauche contact.The differences of glycosylation shifts induced by a mannopyranosyl versus a glucopyranosyl group have been investigated.
- Jansson, Per-Erik,Kenne, Lennart,Persson, Kerstin,Widmalm, Goeran
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p. 591 - 598
(2007/10/02)
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- LYSOSOMAL-ENZYME TARGETING: THE PHOSPHORYLATION OF SYNTHETIC D-MANNOSYL SACCHARIDES BY UDP-N-ACETYLGLUCOSAMINE:LYSOSOMAL-ENZYME N-ACETYLGLUCOSAMINE-PHOSPHOTRANSFERASE FROM RAT-LIVER MICROSOMES AND FIBROBLASTS
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Phosphorylation of the D-mannose residues of lysosomal-enzymes is essential for the uptake and intracellular transport of these enzymes to lysosomes.The GlcNAc-P-transferase which is involved in the phosphorylation reaction seems to recognize a signal, probably a protein conformation, common to many lysosomal enzymes.To evaluate the role of the carbohydrate portion of the enzyme in these phosphorylation reactions, the acceptor specificity of GlcNAc-P-transferase from rat-liver microsomes and fibroblasts was examined with the aid of synthetic D-mannosyl disaccharides and derivatives that are closely related to the high-mannose type of oligosaccharides.Four methyl D-mannobiosides were synthesized, and their structures were established by 13C-n.m.r. spectroscopy.Of all the D-mannosyl saccharides tested, α-D-Man-(1->2)-α-D-Man-(1->OMe) was found to be the best acceptor, thereby suggesting that oligosaccharide structure may also have a role to play in recognition by this enzyme.
- Madiyalakan, Ragupathy,Chowdhary, Manjit S.,Rana, Surjit S.,Matta, Khushi L.
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p. 183 - 194
(2007/10/02)
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- PREPARATION OF α AND Β ANOMERS OF VARIOUS ISOMERIC METHYL O-D-GALACTOPYRANOSYL-D-GALACTOPYRANOSIDES. STANDARDS FOR INTERPRETATION OF 13C-N.M.R. SPECTRA OF D-GALACTOPYRANANS
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The four isomer of methyl O-β-D-galactopyranosyl-β-D-galactopyranoside were prepared by condensation of 2,3,4,6-tetra-O-acetyl-α-galactopyranosyl bromide with appropriate, partially O-substitued derivatives of methyl β-D-galactopyranoside.Reaction of 3,4,6-tri-O-acetyl-1,2-O-(1-ethoxyethylidene)-α-D-galactopyranose with the same acceptors, in the presence of mercuric bromide, led to the formation of α and β linkages.Thus, it was possible to assign 13C-n.m.r. resonances of α and β anomers of methyl O-D-galactopyranosyl-β-D-galactopyranosides.In terms of application of these shift values and those of related D-galactobioses to the structual analysis of D-galactopyranans by shift comparisons, some generalizations can be made.For β-D-galactopyranans, the resonances glycosyloxylated carbon atoms of methyl O-β-D-galactopyranosyl-β-D-galactopyranosides are sensitive to structure and appear to have typical values, whereas limited variation was observed with shift of C-1' signals.On the other hand, for assigning structures to D-galactopyranans containing α linkages, the C-1' shifts (at higher field) of methyl O-α-D-galactopyranosyl-β-D-galactopyranosidesc are sensitive to linkage position, whereas those of glycosyloxylated carbon atoms vary only a little.
- Gorin, Philip A. J.
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