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| Open AccessStereoselective assembly of C-oligosaccharides via modular difunctionalization of glycals
C-oligosaccharides are found in natural products and drug molecules, but their synthesis is challenging. Here, the authors report a strategy for the stereoselective and efficient synthesis of Coligosaccharides via palladium-catalyzed nondirected C1–H glycosylation/C2-alkenylation, cyanation, and alkynylation of 2-iodoglycals with glycosyl chloride donors.
- Ya-Nan Ding
- , Mei-Ze Xu
- & Yong-Min Liang
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| Open AccessCharacterization of elusive rhamnosyl dioxanium ions and their application in complex oligosaccharide synthesis
Characterizing highly-reactive glycosyl cation intermediates and understanding their glycosylation mechanisms are essential to the stereoselective synthesis of complex carbohydrates. Here the authors report a workflow that is utilized to characterize rhamnosyl 1,3-bridged dioxanium ions derived from C-3 p-anisoyl esterified donors.
- Peter H. Moons
- , Floor ter Braak
- & Thomas J. Boltje
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| Open AccessPhotosensitizer-free visible-light-promoted glycosylation enabled by 2-glycosyloxy tropone donors
Visible light-induced glycosylation reactions are achieved by either photoactivating a photosensitizer or using a stoichiometric activator, while glycosylation via a photoactive glycosyl donor was so far not reported. In this study, the authors develop a photosensitizer free visible-light-mediated glycosylation approach using photoactive 2-glycosyloxy tropone as the donor, obtaining a wide range of O-glycosides or oligosaccharides.
- Jing Zhang
- , Zhao-Xiang Luo
- & De-Cai Xiong
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Article
| Open AccessEfficient and versatile formation of glycosidic bonds via catalytic strain-release glycosylation with glycosyl ortho−2,2-dimethoxycarbonylcyclopropylbenzoate donors
Catalytic glycosylation provides access to oligosacchairdes with minimal amount of promoters. Here, the authors developed a new catalytic glycosylation reaction using an ester type donor driven by ring-strain release.
- Han Ding
- , Jian Lyu
- & Xue-Wei Liu
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Article
| Open AccessSynthetic phosphoethanolamine-modified oligosaccharides reveal the importance of glycan length and substitution in biofilm-inspired assemblies
The phosphoethanolamine modified cellulose in E. colibiofilms has revealed that polysaccharide functionalization alters the biofilm properties. Here, the authors show a model system to explore the role of phosphoethanolamine and other unnatural modifications on the properties of the biofilm-inspired assemblies.
- Theodore Tyrikos-Ergas
- , Soeun Gim
- & Martina Delbianco
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Article
| Open AccessStereoselective gold(I)-catalyzed approach to the synthesis of complex α-glycosyl phosphosaccharides
Glycosyl phosphosaccharides represent a large and important family of complex glycans, but are difficult to synthesize efficiently. Here, the authors disclose a stereoselective methodology to make α-glycosyl phosphosaccharides, via gold(I)-catalyzed glycosylation of phosphoric acid acceptors.
- Xiaojuan Zhang
- , Yutong Yang
- & Yugen Zhu
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Article
| Open AccessFacile access to C-glycosyl amino acids and peptides via Ni-catalyzed reductive hydroglycosylation of alkynes
C-Glycosyl peptides/proteins are metabolically stable mimics of the native glycopeptides/proteins of great therapeutic potential, but their chemical synthesis is challenging. Here, the authors report a protocol for the synthesis of vinyl C-glycosyl amino acids and peptides, via a Ni-catalyzed reductive hydroglycosylation reaction of alkyne derivatives of amino acids and peptides with glycosyl bromides.
- Yan-Hua Liu
- , Yu-Nong Xia
- & Biao Yu
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Article
| Open AccessTransforming biorefinery designs with ‘Plug-In Processes of Lignin’ to enable economic waste valorization
The current biorefineries yield lignin with inadequate fractionation for bioconversion, yet substantial changes of these biorefinery designs could jeopardize carbohydrate efficiency and increase capital costs. Here the authors resolve the dilemma by designing ‘plug-in processes of lignin’ to enable economic waste valorization.
- Zhi-Hua Liu
- , Naijia Hao
- & Joshua S. Yuan
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Article
| Open AccessSite-switchable mono-O-allylation of polyols
Selective manipulation of one functional group, out of many repeatedly occurring in a substrate, represents a grand challenge in chemistry. Here, the authors report a Pd/Lewis acid cocatalytic system that achieves not only site-selective, but also site-switchable mono-O-allylation of polyols.
- Hua Tang
- , Yu-Biao Tian
- & Dawen Niu
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Article
| Open AccessTransfer learning enables the molecular transformer to predict regio- and stereoselective reactions on carbohydrates
Organic reactions can readily be learned by deep learning models, however, stereochemistry is still a challenge. Here, the authors fine tune a general model using a small dataset, then predict and validate experimentally regio- and stereo-selectivity for various carbohydrates transformations.
- Giorgio Pesciullesi
- , Philippe Schwaller
- & Jean-Louis Reymond
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Article
| Open AccessCharacterization of glycosyl dioxolenium ions and their role in glycosylation reactions
Dioxolenium ion intermediates formed from remote positions are hypothesized to direct stereoselective glycosylations. Herein we combine infrared ion spectroscopy, DFT calculations and synthetic work to characterize and study these dioxolenium ions and their role in stereoselective glycosylation reactions.
- Thomas Hansen
- , Hidde Elferink
- & Thomas J. Boltje
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| Open AccessDiastereoselective desymmetric 1,2-cis-glycosylation of meso-diols via chirality transfer from a glycosyl donor
Enzyme-catalyzed desymmetric glycosylations are often found in nature, however the corresponding chemical methods are lacking. Here, the authors report a highly diastereoselective desymmetric 1,2-cis-glycosylation of meso-diols found in myo-inositol 1,3,5-orthoesters using a boronic acid catalyst.
- Masamichi Tanaka
- , Koji Sato
- & Kazunobu Toshima
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Article
| Open AccessA Chiron approach towards the stereoselective synthesis of polyfluorinated carbohydrates
Polyfluorinated hexopyranoses display unique physical, chemical and biological properties, however their stereoselective synthesis is highly challenging. Here, the authors report a synthetic approach based on the chemical manipulation of inexpensive levoglucosan to obtain heavily fluorinated monosaccharides stereoselectively.
- Vincent Denavit
- , Danny Lainé
- & Denis Giguère
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Article
| Open AccessUnravelling the structure of glycosyl cations via cold-ion infrared spectroscopy
Glycosyl cations are key intermediates in glycosylation reactions, but their structure has remained elusive due to their transient nature. Here, the authors perform an in-depth structural analysis and report that C2-participating protective groups induce acetoxonium cations with distinct ring conformations.
- Eike Mucha
- , Mateusz Marianski
- & Kevin Pagel
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Article
| Open AccessAn ultra-low thiourea catalyzed strain-release glycosylation and a multicatalytic diversification strategy
Non-covalent glycosyl donor activation often requires high organocatalyst loadings. Here, the authors demonstrate that strain-release glycosylations can take place at very low thiourea catalyst loadings. In addition, the authors developed a one-pot multicatalytic strategy that can diversify glycosides rapidly.
- Chunfa Xu
- & Charles C. J. Loh
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Article
| Open AccessStereoselective oxidative glycosylation of anomeric nucleophiles with alcohols and carboxylic acids
Glycosylation of partially protected sugars is usually limited by suboptimal regio- and stereo-selectivities. Here, the authors show a general oxidative glycosylation between anomeric stannanes with a nonprotected hydroxyl group and oxygen nucleophiles, additionally providing mechanistic insights into the origin of selectivity.
- Tianyi Yang
- , Feng Zhu
- & Maciej A. Walczak
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Article
| Open AccessBacterially derived synthetic mimetics of mammalian oligomannose prime antibody responses that neutralize HIV infectivity
Neutralizing antibodies to oligomannose glycans on HIV Env are difficult to elicit, possibly due to B cell tolerance. Here, Pantophlet et al. synthesize mimetics based on a bacterial oligosaccharide and show that they evoke HIV-neutralizing antibody responses in animals with a human Ig repertoire.
- Ralph Pantophlet
- , Nino Trattnig
- & Paul Kosma
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| Open AccessA minimalist approach to stereoselective glycosylation with unprotected donors
Oligosaccharide synthesis is encumbered by multiple protection and deprotection steps. Here, the authors report a protection-free yet stereoselective and regioselective glycosylation strategy using boron-masked glycosyl donors, and demonstrate efficient synthesis of oligosaccharides over a wide substrate scope.
- Kim Le Mai Hoang
- , Jing-xi He
- & Xue-Wei Liu
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Article
| Open AccessDeciphering minimal antigenic epitopes associated with Burkholderia pseudomallei and Burkholderia mallei lipopolysaccharide O-antigens
Melioidosis and glanders are multifaceted infections caused by gram-negative bacteria. Here, the authors synthesize a series of oligosaccharides that mimic the lipopolysaccharides present on the pathogens’ surface and use them to develop novel glycoconjugates for vaccine development.
- Marielle Tamigney Kenfack
- , Marcelina Mazur
- & Charles Gauthier
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| Open AccessTotal synthesis of mycobacterial arabinogalactan containing 92 monosaccharide units
Due to the vast number of potential isomers, the chemical synthesis of large carbohydrates is challenging. Here the authors report the synthesis of mycobacterial arabinogalactan, a biologically important natural product composed of 92 monosaccharide units, the largest synthetic polysaccharide to date.
- Yong Wu
- , De-Cai Xiong
- & Xin-Shan Ye
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| Open Access[Au]/[Ag]-catalysed expedient synthesis of branched heneicosafuranosyl arabinogalactan motif of Mycobacterium tuberculosis cell wall
Arabinogalactan forms parts of the cellular envelope ofMycobacterium tuberculosis, however due to its size chemical synthesis is a massive task. Here the authors report the synthesis of branched heneicosafuranosyl arabinogalactan fragment by repeated use of a Au/Ag-catalysed glycosylation methodology.
- Shivaji A. Thadke
- , Bijoyananda Mishra
- & Srinivas Hotha
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| Open AccessAutomated assembly of oligosaccharides containing multiple cis-glycosidic linkages
Automated glycan assembly has proven a powerful method to rapidly synthesize large oligosaccharides, though stereoselective cis-glycosylation remains a challenge. Here, the authors demonstrate a system to selectively incorporate multiple cis-glycosidic linkages by use of remote participating groups.
- Heung Sik Hahm
- , Mattan Hurevich
- & Peter H Seeberger
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| Open AccessTetrasaccharide iteration synthesis of a heparin-like dodecasaccharide and radiolabelling for in vivo tissue distribution studies
Heparin-like oligosaccharides are implicated in various diseases. Hansen et al. report an efficient two-cycle [4+4+4] tetrasaccharide-iteration-based approach to synthesize a structurally defined heparin dodecasaccharide with a latent aldehyde tag for labelling and conjugation.
- Steen U. Hansen
- , Gavin J. Miller
- & John M. Gardiner