Synthesis of a common trisaccharide fragment of glycoforms of the outer core region of the Pseudomonas aeruginosa lipopolysaccharide

Komarova, Bozhena S.; Tsvetkov, Yury E.; Knirel, Yuriy A.; Zähringer, Ulrich; Pier, Gerald B.; Nifantiev, Nikolay E.

doi:10.1016/j.tetlet.2006.03.045

Cited by 39 publications

(33 citation statements)

References 14 publications

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“…Thioglycoside acceptor 13 was subjected to AgOTf-promoted glycosylation with imidate 7 to prepare α-glucosyl-(1→6)-glucose block. However, unlike the published data related to AgOTf-promoted glycosylation with similar trichloracetimidates18 and our own previous results,6 AgOTf from a freshly opened package did not promote this glycosylation. We thus assumed that the actual promoter in the cited works was possibly traces of triflic acid, which is produced from AgOTf upon hydrolysis.…”

Section: Resultscontrasting

confidence: 99%

“…> Thus, the most realistic way to 3,4-bisglycosylated GalNAc would include initial 3- O -glycosylation followed by 4- O -glycosylation. As we have shown during the synthesis of trisaccharides 1a – c ,6 the same is true for 2-azido-2-deoxygalactose: the successful preparation of the target structure was possible if β-(1→3)-glucosylation of a galactosamine acceptor preceded α-(1→4)-glucosylation. In contrast, an alternative sequence of glycosylations, which involves β-glucosylation of an α-(1→4)-linked Glc-GalN 3 unit, did not lead at all to the target trisaccharide backbone.…”

Section: Resultsmentioning

confidence: 63%

“…The known benzylidene derivative of 2-azido-2-deoxygalactose 10 6 and β-thioglucoside 13 15 were used as starting materials in the synthesis of the pentasaccharide. A set of α-glucosyl donors, namely N -phenyltrifluoroacetimidates 7 , 5 , and 11 (Scheme 2) with different protecting group patterns, was prepared as follows: Selective benzoylation of the primary hydroxyl group in diol 15 16 afforded 6-monobenzoate 16 , and treatment with N -phenyltrifluoroacetimidoyl chloride (PTAIC) in the presence of potassium carbonate gave glucosyl donor 7 .…”

Section: Resultsmentioning

confidence: 99%

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First Synthesis of Pentasaccharide Glycoform I of the Outer Core Region of the Pseudomonas aeruginosa Lipopolysaccharide

et al. 2008

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The synthesis of a pentasaccharide representing the glycoform I, which is one of two naturally occurring glycoforms of the outer core of Pseudomonas aeruginosa lipopolysaccharide, and its analogues, differing in the N-substituent in the galactosamine unit, is reported. The main features of the synthetic scheme included the assembly of the pentasaccharide backbone by successive introduction of monosaccharide units, the use of glucosyl donors with specific location of acyl protecting groups capable of the remote anchimeric participation for highly stereoselective α-glucosylation, and efficient reduction of the azido group allowing high-yielding transformation of the intermediary azido pentasaccharide into final products.

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Section: Resultscontrasting

confidence: 99%

Section: Resultsmentioning

confidence: 63%

Section: Resultsmentioning

confidence: 99%

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First Synthesis of Pentasaccharide Glycoform I of the Outer Core Region of the Pseudomonas aeruginosa Lipopolysaccharide

et al. 2008

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“…The combined effect of the remote participation of acyl group at O-3 and O-6 of glucosyl donors in glucosylations was investigated by Nifantiev and coworkers in 2006 (18). The glycosylation of 57 with donor 59 having both 3-Oand 6-O-acetyl groups was highly α-selective producing disaccharide 60 (α/β = 8:1) with an excess of the α-anomer (Scheme 10).…”

Section: B the Remote Participation In Glycopyranosylationsmentioning

confidence: 99%

Remote Participation of Protecting Groups at Remote Positions of Donors in Glycosylations

Kim

Suk

2011

TIGG

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Effects of potentially participating groups at remote positions of glycopyranosyl and glycofuranosyl donors on the glycosylation stereochemistry are reviewed. Substantial evidences in favor of the remote participation by protecting groups are presented and also included are a few reports opposed to the remote participation. A. IntroductionT h e p r o t e c t i n g g r o u p s i n t h e o l i g o s a c c h a r i d e synthesis are used to selectively block interfering functions as well as influence the reactivity and stereoselectivity in the glycosylation steps. The anchimeric assistance of a neighboring participating group such as an acyl group at the O-2 position of the glycosyl donor has been one of the most useful strategies for the stereoselective formation of 1,2-trans glycosides (1−5). The carbonyl functionality at the O-2 position of the glycosyl donor can attack an incipient oxonium ion to give a dioxonium ion. Nucleophilic attack by an acceptor to the opposite face of the dioxonium ion provides the 1,2-trans glycoside. When potentially participating groups are located at remote positions other than the O-2 position of glycosyl donors, the existence of the remote participation by the remote protecting groups in the glycosylation step has been controversial. Although numerous examples for glycosylations with glycosyl donors possessing potentially participating groups at remote positions can be found in the literature, most of them do not provide any information on the remote participation by protecting groups in glycosylations. There have been reports both in favor of and opposed to the remote participation by protecting groups in glycosylations. Herein we review the effects of potentially participating protecting groups at remote positions of glycopyranosyl and glycofuranosyl donors on the glycosylation stereochemistry. Further, we present substantial evidence in favor of the remote participation by protecting groups and also include a few reports that are opposed to remote participation.

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“…Methyl 2-azido-2-deoxy-D-galactoside 7 18 was used as a glycosyl acceptor in reactions with glucosyl donors 1 and 2. AgOTf-promoted glycosylation with fully benzylated N-phenyltrifluoroacetimidate 1 ( Table 1, entry 1) afforded a 2:1 mixture of a-and b-isomers 10 and 11 in 95% yield.…”

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confidence: 99%

Stereoselective α-Glycosylation with 3-O-Acetylated d-Gluco Donors

Ustyuzhanina¹,

Komarova²,

Zlotina³

et al. 2006

Synlett

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The effect of a 3-O-acetyl group on the stereoselectivity of a-glycosylation with 2-O-benzylated D-gluco glycosyl donors was studied. It was shown that 3-O-acetylated donors gave a-anomers predominantly or exclusively, whereas glycosylation with the corresponding per-O-benzylated donors afforded mixtures of comparable amounts of a-and b-anomers. The higher a-stereoselectivity in the first case was accounted for by the remote anchimeric assistance of the 3-O-acetyl group, which was confirmed by theoretical calculations.

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Synthesis of a common trisaccharide fragment of glycoforms of the outer core region of the Pseudomonas aeruginosa lipopolysaccharide

Cited by 39 publications

References 14 publications

First Synthesis of Pentasaccharide Glycoform I of the Outer Core Region of the Pseudomonas aeruginosa Lipopolysaccharide

First Synthesis of Pentasaccharide Glycoform I of the Outer Core Region of the Pseudomonas aeruginosa Lipopolysaccharide

Remote Participation of Protecting Groups at Remote Positions of Donors in Glycosylations

Stereoselective α-Glycosylation with 3-O-Acetylated d-Gluco Donors

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