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4 '-Methoxyphenacyl-Assisted Synthesis of beta-Kdo Glycosides

Mazur, Marcelina; Barycza, Barbara; Andriamboavonjy, Hanitra; Lavoie, Serge; Kenfack, Marielle T.; Laroussarie, Anais; Bleriot, Yves; Gauthier, Charles (2016). 4 '-Methoxyphenacyl-Assisted Synthesis of beta-Kdo Glycosides Journal of Organic Chemistry , vol. 81 , nº 22. p. 10585-10599. DOI: 10.1021/acs.joc.6b01431.

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Résumé

3-Deoxy-beta-D-manno-oct-2-ulosonic acid (beta-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 beta-Kdo glycosides via the use of a 4'-methoxyphenacyl (Phen) auxiliary group at the Cl position of a peracetylated beta-Kdo thioglycoside. Under the promotion of NIS/AgOTf in acetonitrile, a series of Kdo glycosides was synthesized in good yield and beta-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 alpha-triflate and a six-membered alpha-spiroPhen are plausible intermediates of the reaction, accounting for the enhanced formation of beta-Kdo glycosides. The developed methodology could be applied to the synthesis of beta-Kdo-containing glycans from pathogenic bacteria.

Type de document: Article
Mots-clés libres: -
Centre: Centre INRS-Institut Armand Frappier
Date de dépôt: 25 févr. 2019 17:01
Dernière modification: 25 févr. 2019 17:01
URI: http://espace.inrs.ca/id/eprint/5556

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