Protecting Group Manipulations in Carbohydrate Synthesis

Csávás, Magdolna; Herczeg, Mihály; Bajza, István; Borbás, Anikó

doi:10.1016/b978-0-12-819475-1.00087-0

Cited by 4 publications

(3 citation statements)

References 473 publications

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“…However, the selectivity is not predictable, mainly because of the many controversial results reported from a variety of examinations using many types of donors suitably optimized to the demand of their targets. Based on basic observations, the solvent effect [174][175][176][177][178][179][180], the concentration effect [181][182][183][184][185], and other factors [186][187][188], including a very recent approach using an S N 2-predicting, leaving group enhanced by a coordinating acceptor [189,190], were also accepted as factors for the stereoselectivity of glycosylation. This review focuses on two effective and stereoselective methods for glucan synthesis: the use of C2-o-tosylamide (TsNH)-benzyl (TAB) ether for bimodal glycosylation [191][192][193] and ZnI 2 -mediated 1,2-cis glycosylation [194].…”

Section: 2-cis Glycosylationmentioning

confidence: 99%

“…factors [186][187][188], including a very recent approach using an SN2-predicting, leaving group enhanced by a coordinating acceptor [189,190], were also accepted as factors for the stereoselectivity of glycosylation. This review focuses on two effective and stereoselective methods for glucan synthesis: the use of C2-o-tosylamide (TsNH)-benzyl (TAB) ether for bimodal glycosylation [191][192][193] and ZnI2-mediated 1,2-cis glycosylation [194].…”

Section: 2-cis Glycosylationmentioning

confidence: 99%

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Recent Progress in 1,2-cis glycosylation for Glucan Synthesis

et al. 2023

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Controlling the stereoselectivity of 1,2-cis glycosylation is one of the most challenging tasks in the chemical synthesis of glycans. There are various 1,2-cis glycosides in nature, such as α-glucoside and β-mannoside in glycoproteins, glycolipids, proteoglycans, microbial polysaccharides, and bioactive natural products. In the structure of polysaccharides such as α-glucan, 1,2-cis α-glucosides were found to be the major linkage between the glucopyranosides. Various regioisomeric linkages, 1→3, 1→4, and 1→6 for the backbone structure, and 1→2/3/4/6 for branching in the polysaccharide as well as in the oligosaccharides were identified. To achieve highly stereoselective 1,2-cis glycosylation, including α-glucosylation, a number of strategies using inter- and intra-molecular methodologies have been explored. Recently, Zn salt-mediated cis glycosylation has been developed and applied to the synthesis of various 1,2-cis linkages, such as α-glucoside and β-mannoside, via the 1,2-cis glycosylation pathway and β-galactoside 1,4/6-cis induction. Furthermore, the synthesis of various structures of α-glucans has been achieved using the recent progressive stereoselective 1,2-cis glycosylation reactions. In this review, recent advances in stereoselective 1,2-cis glycosylation, particularly focused on α-glucosylation, and their applications in the construction of linear and branched α-glucans are summarized.

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Section: 2-cis Glycosylationmentioning

confidence: 99%

Section: 2-cis Glycosylationmentioning

confidence: 99%

Recent Progress in 1,2-cis glycosylation for Glucan Synthesis

et al. 2023

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“…Recent development based on glycosyl donor modifications and reaction conditions for 1,2-cis glycosylation For controlling the stereoselectivity of glycosylation, the protective groups on the donor moiety are well studied as one of the main factors (recent review, Csávás et al, 2021), including chiral auxiliary at 2-position (recent review, Mensink and Boltje, 2017). The cyclic protective groups on diols for the conformationally constrained donors (Jeanneret et al, 2020) could also be used for various glycosyl donors as one of the key stereocontrolling factors for glycosylation.…”

Section: Recent Advances On 12-cis Glycosylations By Intermolecular C...mentioning

confidence: 99%

Recent advances in stereoselective 1,2-cis-O-glycosylations

Ishiwata

Tanaka

et al. 2022

Front. Chem.

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For the stereoselective assembly of bioactive glycans with various functions, 1,2-cis-O-glycosylation is one of the most essential issues in synthetic carbohydrate chemistry. The cis-configured O-glycosidic linkages to the substituents at two positions of the non-reducing side residue of the glycosides such as α-glucopyranoside, α-galactopyranoside, β-mannopyranoside, β-arabinofuranoside, and other rather rare glycosides are found in natural glycans, including glycoconjugate (glycoproteins, glycolipids, proteoglycans, and microbial polysaccharides) and glycoside natural products. The way to 1,2-trans isomers is well sophisticated by using the effect of neighboring group participation from the most effective and kinetically favored C-2 substituent such as an acyl group, although high stereoselective synthesis of 1,2-cis glycosides without formation of 1,2-trans isomers is far less straightforward. Although the key factors that control the stereoselectivity of glycosylation are largely understood since chemical glycosylation was considered to be one of the useful methods to obtain glycosidic linkages as the alternative way of isolation from natural sources, strictly controlled formation of these 1,2-cis glycosides is generally difficult. This minireview introduces some of the recent advances in the development of 1,2-cis selective glycosylations, including the quite recent developments in glycosyl donor modification, reaction conditions, and methods for activation of intermolecular glycosylation, including the bimodal glycosylation strategy for 1,2-cis and 1,2-trans glycosides, as well as intramolecular glycosylations, including recent applications of NAP-ether-mediated intramolecular aglycon delivery.

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Systematic Study of Regioselective Reductive Ring-Opening Reactions of 4,6-O-Halobenzylidene Acetals of Glucopyranosides

et al. 2021

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Reductive openings of cyclic acetals are widely used in modern synthetic organic chemistry for the regioselective introduction of protecting groups. A systematic study was performed on the applicability and efficacy of various hydride donor and protic or Lewis acid reagent combinations in the reductive ring opening of glucosidic 4,6-halobenzylidene acetals bearing an ortho-, meta-, and para-chloro- or -bromo substituent on the benzene ring. Most of the reagent combinations tested cleaved the 4,6-O-halobenzylidene acetal rings at O4 or O6 efficiently and with the expected regioselectivity. The LiAlH4–AlCl3 and the BH3·THF–TMSOTf combinations produced the 4-O-halobenzyl ether/6-OH products with complete regioselectivity and high yields. The use of Me3N·BH3–AlCl3 reagent system in toluene was also effective in cleaving the acetal ring at O6 but was accompanied by Al-chelation-assisted debenzylation side reactions. The NaCNBH3–HCl and the Et3SiH-BF3·Et2O combinations were highly effective in yielding the 6-halobenzyl ether/4-OH derivatives. Et3SiH, in combination with TfOH, produced the 6-O-ether/4-OH products in rapid reactions but also triggered silylation and reductive halobenzylation as secondary transformations. Reductive opening of the 1,3-dioxane ring of pyranosidic 4,6-O-halobenzylidene acetals by the proper reagent combination was found to be an efficient method for the regioselective introduction of versatile halobenzyl protecting groups onto the pyranose ring.

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Protecting Group Manipulations in Carbohydrate Synthesis

Cited by 4 publications

References 473 publications

Recent Progress in 1,2-cis glycosylation for Glucan Synthesis

Recent Progress in 1,2-cis glycosylation for Glucan Synthesis

Recent advances in stereoselective 1,2-cis-O-glycosylations

Systematic Study of Regioselective Reductive Ring-Opening Reactions of 4,6-O-Halobenzylidene Acetals of Glucopyranosides

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