Development of a highly α-selective galactopyranosyl donor based on a rational design

Li, Zhitao; Zhu, Lisheng; Kalikanda, Jane

doi:10.1016/j.tetlet.2011.08.091

Cited by 20 publications

(20 citation statements)

References 28 publications

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“… 25 ) and 13c bearing C6 acetyl or benzoyl esters resulted in lower selectivity ( α : β =6.4−5.8:1) (entries 2 and 3). These results are consistent with reports that C6 esters decrease the α-selectivity of galactose 18 . The presence of a C4-acetyl or benzoyl ester in thiogalactosides 13d and 13e drastically improved the α-selectivity (26.5−26.2:1).…”

Section: Resultssupporting

confidence: 94%

“…Additives can improve stereoselectivity by forming a less reactive intermediate in situ 16 but are hard to use during automated syntheses. Remote participation by protecting groups placed at the C3, C4 and/or C6 positions of glucose (Glc) and galactose (Gal) building blocks can control the stereoselectivity of glycosylations 17 18 19 . Building blocks containing common remote participating groups are attractive for automated synthesis as they fit the coupling–deprotection scheme and require no additional manipulations.…”

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confidence: 99%

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Automated assembly of oligosaccharides containing multiple cis-glycosidic linkages

2016

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Automated glycan assembly (AGA) has advanced from a concept to a commercial technology that rapidly provides access to diverse oligosaccharide chains as long as 30-mers. To date, AGA was mainly employed to incorporate trans-glycosidic linkages, where C2 participating protecting groups ensure stereoselective couplings. Stereocontrol during the installation of cis-glycosidic linkages cannot rely on C2-participation and anomeric mixtures are typically formed. Here, we demonstrate that oligosaccharides containing multiple cis-glycosidic linkages can be prepared efficiently by AGA using monosaccharide building blocks equipped with remote participating protecting groups. The concept is illustrated by the automated syntheses of biologically relevant oligosaccharides bearing various cis-galactosidic and cis-glucosidic linkages. This work provides further proof that AGA facilitates the synthesis of complex oligosaccharides with multiple cis-linkages and other biologically important oligosaccharides.

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Section: Resultssupporting

confidence: 94%

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confidence: 99%

Automated assembly of oligosaccharides containing multiple cis-glycosidic linkages

2016

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“…Infrared spectra were obtained as a film on NaCl plates in the region 4000-400 cm -1 on a Nicolet Impact 400D spectrophotometer. Compounds 4, 1 5a 2 , 5c 3 and 8 4 were prepared according to their literature procedures and experimental details are in agreement with the reported values.…”

Section: General Methodssupporting

confidence: 55%

“…Galactosyl thiophenyl ethers 4, 32 8, 33 and 9 34 were selected as glycosyl donors suitable for 1,2-cis glycoside formation (Figure 1, see ESI for optimized synthetic procedures). Compounds 8 and 9 are functionalized with orthogonal protecting groups 35 and allow different reactivity regarding anomeric selectivity based on remote group participation compared to perbenzylated thioglycoside 4.…”

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confidence: 99%

Glycosylated α-Azido Amino Acids: Versatile Intermediates in the Synthesis of Neoglycoconjugates

O’Flaherty

Velasco‐Torrijos

2018

Synlett

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A series of glycosylated α-azido amino acids was synthesized as precursors for neoglycoconjugates, a class of important biomolecules for drug discovery, and sensor development. The synthetically challenging 1,2-cis α-galactosylated species described herein were designed as building blocks in the synthesis of analogues of α-galactosyl ceramide, a potent immunomodulator. A benzyl-protected 1,2,3-triazolyl α-galactosyl-l-serine derivative was prepared using copper azide alkyne cycloaddition to showcase the potential of glycosylated α-azido amino acids in neoglycoconjugate design.

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“…Allyl protection was selected to mask the anomeric position of 16 while former PMB‐protected C2 position and TBDPS‐protection at the C6 position guarantee orthogonal masking of the connection points (PMB= p ‐methoxybenzyl) To ensure high α‐selectivity during galactosylations, a remote participating benzoyl ester group was introduced at C4 position of the galactosyl donor …”

Section: Resultsmentioning

confidence: 99%

Synthesis of Galactosylated Glycosylphosphatidylinositol Derivatives from Trypanosoma brucei

Grube

Lee

Michel

et al. 2018

Chemistry A European J

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Trypanosoma brucei uses variant surface glycoproteins (VSGs) to evade the host immune system and ensure parasitic longevity in animals and humans. VSGs are attached to the cell membrane by complex glycosylphosphatidylinositol anchors (GPI). Distinguishing structural feature of VSG GPIs are multiple α- and β-galactosides attached to the conserved GPI core structure. T. brucei GPIs have been associated with macrophage activation and alleviation of parasitemia during infection, acting as disease onset delaying antigens. Literature reports that link structural modifications in the GPIs to changes in biological activity are contradictory. We have established a synthetic route to prepare structurally overlapping GPI derivatives bearing different T. brucei characteristic structural modifications. The GPI collection will be used to assess the effect of galactosylation and phosphorylation on T. brucei GPI immunomodulatory activity, and to perform an epitope mapping of this complex glycolipid as potential diagnostic marker for Trypanosomiasis. A strategy for the synthesis of a complete α-tetragalactoside using the 2-naphthylmethyl protecting group and for subsequent attachment of GPI fragments to peptides is presented.

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Development of a highly α-selective galactopyranosyl donor based on a rational design

Cited by 20 publications

References 28 publications

Automated assembly of oligosaccharides containing multiple cis-glycosidic linkages

Automated assembly of oligosaccharides containing multiple cis-glycosidic linkages

Glycosylated α-Azido Amino Acids: Versatile Intermediates in the Synthesis of Neoglycoconjugates

Synthesis of Galactosylated Glycosylphosphatidylinositol Derivatives from Trypanosoma brucei

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