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4 results on '"DEHYDRATIVE GLYCOSYLATION"'

1. Trichloroisocyanuric acid (TCCA): A Suitable Reagent for Direct Glycosylations of C1‐Hemiacetals with Different Nucleophiles.

Author

Khanam, Ariza, Javed, Lal, Mohan, and Kumar Mandal, Pintu

Subjects
GLYCOSYLATION, NUCLEOPHILES, NUCLEAR magnetic resonance, MASS spectrometry, NUCLEAR magnetic resonance spectroscopy, FUNCTIONAL groups, PHENOL content of food
Abstract

Trichloroisocyanuric acid (TCCA), a readily accessible, inexpensive, shelf‐stable, and non‐toxic reagent in combination with PPh3, has been used for dehydrative glycosylation reactions with furanose, pyranose, and deoxy‐sugar hemiacetals. The methodology provides a mild reaction condition, good functional group tolerance, featuring a wide variety of substrate scope using O‐, C‐, N‐, and S‐based nucleophiles with good to excellent yields and majority α‐selectivity in case of O‐glycosides while the stereoselectivity in case of C‐, N‐ and S‐ glycosides depends upon the nature of nucleophiles. Notably, this mild dehydrative glycosylation system also provides a reliable method for the synthesis of challenging phenolic glycosides. The progress of the dehydrative glycosylation reaction was monitored by mass and NMR spectroscopy and it is hypothesized that alkoxyphosphonium ions might be the reactive intermediate formed in this process, supported by 31P nuclear magnetic resonance studies. [ABSTRACT FROM AUTHOR]

Published
2023
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2. A dehydrative glycosylation protocol mediated by nonafluorobutanesulfonyl fluoride (NfF).

Author

Tang, Yu, Reddy, D. Prabhakar, and Yu, Biao

Subjects
*GLYCOSYLATION, *HEMIACETALS
Abstract

A new dehydrative glycosylation protocol that proceeds through selective activation of glycosyl hemiacetals with nonafluorobutanesulfonyl fluoride (NfF) has been disclosed. Contrary to the major classical glycosylation reactions that proceed under acidic or neutral conditions, the present glycosylation reaction proceeds under mild basic conditions. In the absence of an external acceptor, self-condensation of the glycosyl hemiacetal occurs, providing the corresponding symmetrical 1,1′-disaccharides in high yields. Image 1 [ABSTRACT FROM AUTHOR]

Published
2021
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3. Influence of O6 in Mannosylations Using Benzylidene Protected Donors

Author

Christian Pedersen, Jeroen D. C. Codée, Marthe T. C. Walvoort, Tobias Gylling Frihed, Gijs A. van der Marel, Mikael Bols, and Chemical Biology 2

Subjects
Reaction mechanism, Mannosides, Magnetic Resonance Spectroscopy, C-GLYCOSYLATION, SULFOXIDE METHOD, Stereochemistry, Reactive intermediate, Sulfonium Compounds, Ring (chemistry), CONJUGATE REDUCTION, Benzylidene Compounds, DEHYDRATIVE GLYCOSYLATION, STEREOSELECTIVE SYNTHESIS, Molecule, Reactivity (chemistry), BETA-D-MANNOPYRANOSIDES, Ions, GLYCOSIDE REACTIVITY, Chemistry, STEREOCONTROLLED SYNTHESIS, Organic Chemistry, Stereoisomerism, BOND FORMATION, Stereoselectivity, ELECTROSTATIC INTERACTIONS, Selectivity, Mannose
Abstract

The stereoselective synthesis of beta-mannosides and the underlying reaction mechanism have been thoroughly studied, and especially the benzylidene-protected mannosides have gained a lot of attention since the corresponding mannosyl triflates often give excellent selectivity. The hypothesis for the enhanced stereoselectivity has been that the benzylidene locks the molecule in a less reactive conformation with the O6 trans to the ring oxygen (O5), which would stabilize the formed alpha-triflate and subsequent give beta-selectivity. In this work, the hypothesis is challenged by using the carbon analogue (C7) of the benzylidene-protected mannosyl donor, which is investigated in terms of diastereoselectivity and reactivity and by low-temperature NMR In terms of diastereoselectivity, the C-7-analogue behaves similarly to the benzylidene-protected donor, but its low-temperature NMR reveals the formation of several reactive intermediate. One of the intermediates was found to be the beta-oxosulfonium ion. The reactivity of the donor was found to be in between that of the "torsional" disarmed and an armed donor.

Published
2013

4. Mannosazide Methyl Uronate Donors. Glycosylating Properties and Use in the Construction of beta-ManNAcA-Containing Oligosaccharides

Author

Gijsbert A. van der Marel, Gerrit Lodder, Herman S. Overkleeft, Marthe T. C. Walvoort, Jeroen D. C. Codée, and Chemical Biology 2

Subjects
Glycosylation, Magnetic Resonance Spectroscopy, Anomer, Stereochemistry, REPEATING-UNIT, Disaccharide, Oligosaccharides, Chemical synthesis, chemistry.chemical_compound, YTTERBIUM(III) TRIFLATE, DEHYDRATIVE GLYCOSYLATION, MICROCOCCUS-LUTEUS, INFLUENZAE TYPE-D, chemistry.chemical_classification, Hexuronic Acids, Organic Chemistry, Stereoisomerism, Nuclear magnetic resonance spectroscopy, Oligosaccharide, CELL-WALLS, CAPSULAR POLYSACCHARIDE, STEREOSELECTIVE-SYNTHESIS, Uronic Acids, Carbohydrate Sequence, chemistry, Aldose, Hemiacetal, ENTEROBACTERIAL COMMON-ANTIGEN, CHEMICAL-SYNTHESIS
Abstract

Mannosazide methyl uronate donors equipped with a variety of anomeric leaving groups (beta- and a-S-phenyl, beta- and alpha-N-phenyltrifluoroacetimidates, hydroxyl, P-sulfoxide, and (R-s)- and (S-s)-alpha-sulfoxides) were subjected to activating conditions, and the results were monitored by H-1 NMR. While the S-phenyl and imidate donors all gave a conformational mixture of anomeric alpha-triflates, the hemiacetal and beta- and alpha-sulfoxides produced an oxosulfonium triflate and beta- and alpha-sulfonium bistriflates, respectively. The beta-S-phenyl mannosazide methyl uronate performed best in both activation experiments and glycosylation studies and provided the 1,2-cis mannosidic linkage with excellent selectivity. Consequently, an alpha-Glc-(l -> 4)-,beta-ManN(3)A-SPh disaccharide, constructed by the stereo-selective glycosylation of a 6-O-Fmoc-protected glucoside and beta-S-phenyl mannosazide methyl uronate, was used as the repetitive donor building block in the synthesis of tri-, penta-, and heptasaccharide fragments corresponding to the Micrococcus luteus teichuronic acid.

Published
2010

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