A study of silver (I) perchlorate as an effective promoter for chemical glycosylation with thioimidates and thioglycosides

A critical review of the state-of-the-art evidence in support of the mechanisms of glycosylation reactions is provided. Factors affecting the stability of putative oxocarbenium ions as intermediates at the S1 end of the mechanistic continuum are first surveyed before the evidence, spectroscopic and indirect, for the existence of such species on the time scale of glycosylation reactions is presented. Current models for diastereoselectivity in nucleophilic attack on oxocarbenium ions are then described. Evidence in support of the intermediacy of activated covalent glycosyl donors is reviewed, before the influences of the structure of the nucleophile, of the solvent, of temperature, and of donor-acceptor hydrogen bonding on the mechanism of glycosylation reactions are surveyed. Studies on the kinetics of glycosylation reactions and the use of kinetic isotope effects for the determination of transition-state structure are presented, before computational models are finally surveyed. The review concludes with a critical appraisal of the state of the art.

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The Experimental Evidence in Support of Glycosylation Mechanisms at the S_N1–S_N2 Interface

Adero

et al. 2018

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4′-Methoxyphenacyl-Assisted Synthesis of β-Kdo Glycosides

et al. 2016

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3-Deoxy-β-d-manno-oct-2-ulosonic acid (β-Kdo) glycosides are mainly found in capsular polysaccharides and extracellular exopolysaccharides from Gram-negative bacteria. These compounds have profound biological implications in immune response and act as virulence factors. We have developed a novel methodology for the stereoselective synthesis of β-Kdo glycosides via the use of a 4'-methoxyphenacyl (Phen) auxiliary group at the C1 position of a peracetylated β-Kdo thioglycoside. Under the promotion of NIS/AgOTf in acetonitrile, a series of Kdo glycosides was synthesized in good yield and β-selectivity while minimizing the formation of undesirable glycals. Stereoselectivity of the glycosylation was shown to be modulated by various factors such as promotor, solvent, anomeric ratio of donor, nature of acceptor, and Phen substitution. Chemoselective cleavage of the Phen group was performed under the action of Zn/HOAc. DFT calculations together with experimental results suggested that α-triflate and a six-membered α-spiroPhen are plausible intermediates of the reaction, accounting for the enhanced formation of β-Kdo glycosides. The developed methodology could be applied to the synthesis of β-Kdo-containing glycans from pathogenic bacteria.

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Blue Light Photocatalytic Glycosylation without Electrophilic Additives

Wen

Crich

2017

Org. Lett.

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Photocatalytic formation of glycosidic bonds employing stable and readily accessible O-glycosyl derivatives of 2,2,6,6-tetramethylpiperidin-1-ol is presented that employs an iridium-based photocatalyst and blue LEDs. The reaction proceeds at room temperature and in the absence of additives other than 4 Å molecular sieves. Stereoselectivities are modest but nevertheless dependent on the anomeric configuration of the donor suggesting a substantial degree of concerted character.

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A study of silver (I) perchlorate as an effective promoter for chemical glycosylation with thioimidates and thioglycosides

Cited by 4 publications

References 61 publications

The Experimental Evidence in Support of Glycosylation Mechanisms at the S_N1–S_N2 Interface

The Experimental Evidence in Support of Glycosylation Mechanisms at the S_N1–S_N2 Interface

4′-Methoxyphenacyl-Assisted Synthesis of β-Kdo Glycosides

Blue Light Photocatalytic Glycosylation without Electrophilic Additives

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A study of silver (I) perchlorate as an effective promoter for chemical glycosylation with thioimidates and thioglycosides

Cited by 4 publications

References 61 publications

The Experimental Evidence in Support of Glycosylation Mechanisms at the SN1–SN2 Interface

The Experimental Evidence in Support of Glycosylation Mechanisms at the SN1–SN2 Interface

4′-Methoxyphenacyl-Assisted Synthesis of β-Kdo Glycosides

Blue Light Photocatalytic Glycosylation without Electrophilic Additives

Contact Info

Product

Resources

About

The Experimental Evidence in Support of Glycosylation Mechanisms at the S_N1–S_N2 Interface

The Experimental Evidence in Support of Glycosylation Mechanisms at the S_N1–S_N2 Interface