Expedient synthesis of a pentasaccharide related to the O-specific polysaccharide of Escherichia coli O117:K98:H4 strain

Bhaumik, Ishani; Misra, Anup Kumar

doi:10.1039/c4ra10538a

Cited by 5 publications

(4 citation statements)

References 41 publications

(34 reference statements)

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“…Analogously, Misra and Bhaumik carried out a one-pot assembly of a pentasaccharide derivative employing two stereoselective glycosylations and in situ removal of a PMB group. 456 Here the thioglycosides are attractive building blocks because both glycosyl donors and acceptors can be activated by NIS in the glycosylation process. As outlined in Scheme 74, the Lfucosyl thioglycoside donor 395 was preferentially activated by NIS and coupled to the trisaccharide acceptor 394.…”

Section: Protection−glycosylation In One-potmentioning

confidence: 99%

“One-Pot” Protection, Glycosylation, and Protection–Glycosylation Strategies of Carbohydrates

et al. 2018

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Carbohydrates, which are ubiquitously distributed throughout the three domains of life, play significant roles in a variety of vital biological processes. Access to unique and homogeneous carbohydrate materials is important to understand their physical properties, biological functions, and disease-related features. It is difficult to isolate carbohydrates in acceptable purity and amounts from natural sources. Therefore, complex saccharides with well-defined structures are often most conviently accessed through chemical syntheses. Two major hurdles, regioselective protection and stereoselective glycosylation, are faced by carbohydrate chemists in synthesizing these highly complicated molecules. Over the past few years, there has been a radical change in tackling these problems and speeding up the synthesis of oligosaccharides. This is largely due to the development of one-pot protection, one-pot glycosylation, and one-pot protection-glycosylation protocols and streamlined approaches to orthogonally protected building blocks, including those from rare sugars, that can be used in glycan coupling. In addition, new automated strategies for oligosaccharide syntheses have been reported not only for program-controlled assembly on solid support but also by the stepwise glycosylation in solution phase. As a result, various sugar molecules with highly complex, large structures could be successfully synthesized. To summarize these recent advances, this review describes the methodologies for one-pot protection and their one-pot glycosylation into the complex glycans and the chronological developments associated with automated syntheses of oligosaccharides.

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Section: Protection−glycosylation In One-potmentioning

confidence: 99%

“One-Pot” Protection, Glycosylation, and Protection–Glycosylation Strategies of Carbohydrates

et al. 2018

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“…In all the glycosylations, only one stereoisomer of the glycosides formed were reported, either obtained as 1,2- trans -glycosides by neighboring group participation or as 1,2- cis -glycosides by solvent effects in 1:1 Et 2 O/CH 2 Cl 2 . This method has since been used in the synthesis of a wide range of natural products by the Misra group − and Mandal , to selectively obtain the axial glycosidic bonds as the only stereoisomer in all the above-mentioned examples, seemingly only requiring changes in the ratio of the Et 2 O/CH 2 Cl 2 solvent mixture. The formation of the undesired 1,2- trans -glycoside was reported as a 5% byproduct in two cases. , Thus, NOBF 4 appears to be an robust catalyst for axial glycosidic bond-formation in ethereal solvents but is yet to be utilized by other research groups.…”

Section: Glycosyl Imidate Donorsmentioning

confidence: 99%

Catalytic Glycosylations in Oligosaccharide Synthesis

2018

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Catalytic glycosylation has been a central reaction in carbohydrate chemistry since its introduction by Fischer 125 years ago, but it is only in the past three to four decades that catalytic methods for synthesizing oligosaccharides have appeared. Despite the development of numerous elegant and ingenious catalytic glycosylation methods, only a few are in general use. This review covers all methods of catalytic glycosylation with the focus on the development and application in oligosaccharide synthesis and provide an overview of the scope and limitations of these. The review also includes relevant mechanistic studies of catalytic glycosylations. The future of catalytic glycosylation chemistry is discussed, including specific, upcoming methods and possible directions for the field of research in general.

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“…NMR spectral analysis of compound 13 unambiguously confirmed its formation.F urther trans-esterification of compound 13 using sodium methoxide [41] gave the tetrasaccharide acceptor 14 in 90 %y ield. Iodonium-ion-mediated stereoselective glycosylation of compound 14 with the l-rhamnosyl thioglycoside 4 in the presence of ac ombination [38] of NIS and HClO 4 /SiO 2 ,f ollowed by in situ removal of the PMB group [32,42] by increasing the reactiont emperature, furnishedt he pentasaccharide acceptor 15 in 72 %y ield. The formation of compound 15 was unambiguously supported by its NMR spectral analysis.…”

mentioning

confidence: 99%

“…The presence of an O-acetoxyg roup at C-2 position of the thioglycoside donor 4 directed the formation of exclusively 1,2-trans glycosylation product by the neighboring group participation. Repetition of the stereoselective glycosylation of compound 15 with compound 4 followed by the in situ removal of PMB group in one pot [32,42] in the presence of ac ombination [38] of NIS and HClO 4 /SiO 2 furnished hexasaccharide acceptor 16 in 70 %y ield. Finally,s tereoselective glycosylation of compound 16 with d-glucosyl thioglycoside donor 7,i n the presence of ac ombination [38] .…”

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confidence: 99%

Synthesis of the Heptasaccharide Repeating Unit of the Cell Wall O‐Polysaccharide of Enterotoxigenic Escherichia coli O139

Ghosh

Misra

2015

ChemistryOpen

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Enterotoxigenic Escherichia coli (ETEC) like the O139 strain are mostly responsible for traveler's diarrhea and causes diseases in pigs, cattle, and poultry. A convenient synthetic strategy was developed for the synthesis of the heptasaccharide repeating unit of the cell wall lipopolysaccharide of the E. coli O139 strain. The p‐methoxybenzyl (PMB) group was used as a temporary protecting group which was removed in situ under the glycosylation conditions by changing the reaction temperature during the synthesis of the target compound. All glycosylation steps gave high yields with good stereoselectivity. A (2,2,6,6‐tetramethylpiperidin‐1‐yl)oxyl (TEMPO)‐mediated selective oxidation of the primary hydroxyl group was carried out using a biphasic reaction condition at the late stage of the synthesis. Such synthetic oligosaccharides could later be effectively conjugated with proteins to prepare glycoconjugate derivatives as vaccine candidates.

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Expedient synthesis of a pentasaccharide related to the O-specific polysaccharide of Escherichia coli O117:K98:H4 strain

Cited by 5 publications

References 41 publications

“One-Pot” Protection, Glycosylation, and Protection–Glycosylation Strategies of Carbohydrates

“One-Pot” Protection, Glycosylation, and Protection–Glycosylation Strategies of Carbohydrates

Catalytic Glycosylations in Oligosaccharide Synthesis

Synthesis of the Heptasaccharide Repeating Unit of the Cell Wall O‐Polysaccharide of Enterotoxigenic Escherichia coli O139

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