2005
DOI: 10.1055/s-2005-868514
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Enhanced Sialylating Activity of O-Chloroacetylated 2-Thioethyl Sialosides

Abstract: It has been shown that O-chloroacetyl protecting groups enhance significantly sialylating activity of 2-thioethyl sialosides in model reactions of a(2-8)-sialylation. Ethyl 4,7,8,9-tetra-O-chloroacetyl-3,5-dideoxy-2-thio-5-trifluoroacetamido-D-glycero-a-D-galacto-non-2-ulopyranoside that combines electron-withdrawing Ochloroacetyl and N-trifluoroacetyl protecting groups displayed the best reactivity and enabled the most efficient synthesis of the Neu5Aca(2-8)Neu5Ac dimer. The GD 3 tetrasaccharide was synthesiz… Show more

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Cited by 27 publications
(15 citation statements)
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“…By increasing the molar amount of 28 to 1.5 equiv,t he yield of 31 was increased to 90 %. This result is in good accordance with the previousg lycosidation reported by Ts vetkov et al [21] using at etra-O-CAc sialic acid donor.T hese results indicated that modifying the glycerol chain (C7-C9) has ap rofounde ffect on the stereoselectivity of the sialoside formation. The poor a-selectivity of 27 could be explained by the oxocarbenium ion from 27 being stable because of the electron donating acetonide moiety and not coordinating with acetonitrile.…”
Section: Resultssupporting
confidence: 95%
“…By increasing the molar amount of 28 to 1.5 equiv,t he yield of 31 was increased to 90 %. This result is in good accordance with the previousg lycosidation reported by Ts vetkov et al [21] using at etra-O-CAc sialic acid donor.T hese results indicated that modifying the glycerol chain (C7-C9) has ap rofounde ffect on the stereoselectivity of the sialoside formation. The poor a-selectivity of 27 could be explained by the oxocarbenium ion from 27 being stable because of the electron donating acetonide moiety and not coordinating with acetonitrile.…”
Section: Resultssupporting
confidence: 95%
“…[10] In addition, Ts vetkova nd co-workersh ave reported that O-chloroacetylprotected sialyl donors exhibit improved reactivity and a-selectivity in sialylation in comparison with the O-acetyl sialyl donor. [11] These resultss uggested to us that the O-acyl protecting groups at the a-face interfere with the a-selective glycosidation by blocking the a-face of the oxoniumcation. We envisaged that sialyl donors that contained no O-acyl protecting groups would have the ability to undergo a-selective glycosidation in the absence of an itrile solvente ffect.…”
Section: Introductionmentioning
confidence: 90%
“…On the other hand, in 2012, De Meo and co‐workers reported that an N ‐acetyl thiosialoside possessing a tert ‐butyldimethylsilylether at the C4 position showed a preference for α‐stereoselectivity when CH 2 Cl 2 was used as the solvent . In addition, Tsvetkov and co‐workers have reported that O ‐chloroacetyl‐protected sialyl donors exhibit improved reactivity and α‐selectivity in sialylation in comparison with the O ‐acetyl sialyl donor . These results suggested to us that the O ‐acyl protecting groups at the α‐face interfere with the α‐selective glycosidation by blocking the α‐face of the oxonium cation.…”
Section: Introductionmentioning
confidence: 94%
“…the sialylation of glycoconjugates, the role of sialyl Lewis x in inflammation and the involvement of N-acetylneuraminic acid (5-acetamido-3,5-dideoxy-D-glycero-D-galacto-non-2-ulopyranosonic acid) in infection by influenza virus. 2-thio glycosides: [372][373][374] Somewhat surprisingly, a TCA is not a useful donor for sialoside synthesis. We have already discussed the synthesis of a sialoside (utilizing a glycosyl ester as a donor), and some of the common donors discussed earlier in this chapter are also employed, e.g.…”
Section: -Deoxy Glycosidesmentioning
confidence: 99%