Correction to Completely β-Selective Glycosylation Using 3,6-<i>O</i>-(<i>o</i>-Xylylene)-Bridged Axial-Rich Glucosyl Fluoride

Okada, Yasunori; Asakura, Noriaki; Bando, Masafumi; Ashikaga, Yoshiki; Yamada, Hidetoshi

doi:10.1021/ja4050746

Cited by 3 publications

(2 citation statements)

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“…7 A similar strategy was employed by Yamada, who used O-xylylene to lock a sugar ring into an axial-rich configuration. 8 In this case, steric factors were used instead as 1,2-cis repulsion with 2-O-benzyl can drive the formation of β-anomers through isomerization after glycosylation.…”

Section: ■ Donor-controlled Glycosylationmentioning

confidence: 99%

Venturing beyond Donor-Controlled Glycosylation: New Perspectives toward Anomeric Selectivity

et al. 2018

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Glycans are complex compounds consisting of sugars linked glycosidically, existing either as pure polysaccharides or as part of glycoconjugates. They are prevalent in nature and possess important functions in regulating biological pathways. However, their diversity coupled with physiochemical similarities makes it challenging to isolate them in large quantities for biochemical studies, hence hampering progress in glycobiology and glycomedicine. Glycochemistry presents an alternative strategy to obtain pure glycan compounds through artificial synthetic methods. Efforts in glycochemistry have been centered on glycosylation, the key reaction in glycochemistry, especially with regards to anomeric stereoselectivity in polysaccharides and glycoconjugates. In particular, the stereoelectronic and steric properties of glycosyl donors are commonly used to direct the stereoselectivity in glycosylation reactions. Classic glycosylation strategies typically involve saturated glycosyl donors, proceeding either directly using hydrogen bonds and conformational constraints or indirectly by installing moieties covalently through neighboring group participation and intramolecular aglycon delivery. Over the past years, new glycosylation strategies, tapping on the foundations of transition metal catalysis, have emerged. To leverage the power of coordination chemistry, unsaturated glycosyl donors were introduced. Not only are the number of protection/deprotection steps reduced, the resultant unsaturated glycoside provides opportunities for downstream functionalizations, allowing quick access to a variety of sugars, including rare sugars. Alongside the glycosyl donor, an equally important but neglected aspect for targeting stereoselective glycosylation is the glycosyl acceptor. In the case of dual-directing donors, glycosyl acceptors have proved themselves capable of becoming the dominating factor for stereocontrol. Interestingly, rational manipulation or selection of glycosyl acceptors with particular nucleophilicity and p K values can lead to different stereoselectivities, thereby proving the tunability of such acceptors to favor the formation of one anomer over the other stereoselectively. By further venturing beyond substrate controlled stereoselectivity, we are presented with the opportunity to effect stereoselective glycosylation through glycosylating reagents. Of the key reagents, stereoselective catalyst stands out as a greener and efficient alternative to direct stereoselective control with stoichiometric substrates. Recently, investigations into this approach of stereocontrol presented an intriguing range of stereoselectivities, achieved by merely varying the nature of catalysts used. Another crucial effort in glycochemistry is enhancing the efficiencies of glycosylations, by reducing the number of preparative steps before or during glycosylation. Through using transient masking groups or one-pot synthetic strategies, these streamlined approaches provide enormous convenience and practicability for oligosaccharide syntheses. Th...

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Section: ■ Donor-controlled Glycosylationmentioning

confidence: 99%

Venturing beyond Donor-Controlled Glycosylation: New Perspectives toward Anomeric Selectivity

et al. 2018

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“…Glycosyl fluorides were also employed recently in a β-stereospecific glycosylation of a conformationally locked, highly reactive glycosyl donor by the Yamada group, utilizing in situ formation of the HB(C 6 F 5 ) 4 catalyst initially introduced by Mukaiyama and co-workers. 341 Schepartz and Miller have recently shown that unprotected glycosyl fluorides serve as excellent glycosyl donors in glycosylations in an aqueous trimethylamine solution in the presence of calcium ions with unprotected sucrose as the acceptor. 342 The ability of glycosyl fluorides to be feasible glycosyl donors in water highlights the good stability of these donors, which offers great versatility.…”

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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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Correction to Completely β-Selective Glycosylation Using 3,6-O-(o-Xylylene)-Bridged Axial-Rich Glucosyl Fluoride

Okada¹,

Asakura²,

Bando³

et al. 2013

J. Am. Chem. Soc.

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Correction to Completely β-Selective Glycosylation Using 3,6-O-(o-Xylylene)-Bridged Axial-Rich Glucosyl Fluoride

Cited by 3 publications

References 1 publication

Venturing beyond Donor-Controlled Glycosylation: New Perspectives toward Anomeric Selectivity

Venturing beyond Donor-Controlled Glycosylation: New Perspectives toward Anomeric Selectivity

Catalytic Glycosylations in Oligosaccharide Synthesis

Correction to Completely β-Selective Glycosylation Using 3,6-O-(o-Xylylene)-Bridged Axial-Rich Glucosyl Fluoride

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