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The efficient synthesis of N‐glycosides via direct N‐glycosylation of amides/azacycles has been reported. The glycosylation of amides/azacycles with glycosyl halides in the presence of a catalytic amount of urea proceeded smoothly to provide the corresponding N‐glycosylated amides or nucleosides in good to excellent yields with 1,2‐trans‐stereoselectivity. Moreover, by the addition of terpyridine, the 1,2‐cis‐stereoselectivity was achieved. [ABSTRACT FROM AUTHOR]

The photoinitiated intramolecular hydroetherification of alkenols has been used to form C−O bonds, but the intermolecular hydroetherification of alkenes with alcohols remains an unsolved challenge. We herein report the visible‐light‐promoted 2‐deoxyglycosylation of alcohols with glycals. The glycosylation reaction was completed within 2 min in a high quantum yield (ϕ=28.6). This method was suitable for a wide array of substrates and displayed good reaction yields and excellent stereoselectivity. The value of this protocol was further demonstrated by the iterative synthesis of 2‐deoxyglycans with α‐2‐deoxyglycosidic linkages up to a 20‐mer in length and digoxin with β‐2‐deoxyglycosidic linkages. Mechanistic studies indicated that this reaction involved a glycosyl radical cation intermediate and a photoinitiated chain process. [ABSTRACT FROM AUTHOR]

Glycans have been hot topics in recent years due to their exhibition of numerous biological activities. However, the heterogeneity of their natural source and the complexity of their chemical synthesis impede the progress in their biological research. Thus, the development of glycan assembly strategies to acquire plenty of structurally well‐defined glycans is an important issue in carbohydrate chemistry. In this review, the latest advances in glycan assembly strategies from concepts to their applications in carbohydrate synthesis, including chemical and enzymatic/chemo‐enzymatic approaches, as well as solution‐phase and solid‐phase/tag‐assisted synthesis, are summarized. Furthermore, the automated glycan assembly techniques are also outlined. [ABSTRACT FROM AUTHOR]

A new glycosylation method promoted by visible light with 3,5-dimethoxyphenyl glycoside as the donor was developed. This protocol delivers both O-glycosides and N-glycosides in moderate to excellent yields using a wide range of O-nucleophiles and nucleobases as the glycosyl acceptors. [ABSTRACT FROM AUTHOR]

Carbohydrates have gained a lot of appreciation in the past few decades due to their important roles in numerous biological events. Acquiring a structurally well‐defined carbohydrate compound is essential for the understanding of its functions. Although some innovative methods have been developed for the synthesis of complex oligosaccharides, glycan synthesis is in general still a time‐consuming and difficult work. Herein, we will introduce the preactivation‐based glycosylation strategy, which is an efficient protocol independent of the reactivity of glycosyl donor. This review will focus on summarizing the versatile applications of preactivation strategy in stereoselective glycosylation and one‐pot assembly of biologically important oligosaccharides and even polysaccharides. What is the most favorite and original chemistry developed in your research group? Preactivation‐based one‐pot glycosylation strategy and applications. How do you get into this specific field? Could you please share some experiences with our readers? I got into this field when I was a research associate in 1996. My supervisor, Prof. Chi‐Huey Wong, gave me a research topic for synthesis of oligosaccharide libraries. At that moment, as a beginner, I did not know too much carbohydrate chemistry, just to learn and to do it. The importance and challenge of carbohydrates attracted me. What is the most important personality for scientific research? Curiosity, passion, and creative thinking. How do you supervise your students? In my opinion, before the graduate students start a specific project, their experimental skills need to be well trained. During the period of graduate studies, the enhancement of abilities to analyze problems and to solve problems is very important. The graduate students should always keep an eye on the unusual experimental phenomena. What's your hobbies? Reading history books. What is your favorite journals? The journals publishing the latest research works in chemistry and medical science. [ABSTRACT FROM AUTHOR]

We report a novel and highly stereoselective electro‐2‐deoxyglycosylation from glycals. This method features excellent stereoselectivity, scope, and functional‐group tolerance. This process can also be applied to the modification of a wide range of natural products and drugs. Furthermore, a scalable synthesis of glycosylated podophyllotoxin and a one‐pot trisaccharide synthesis through iterative electroglycosylations were achieved. [ABSTRACT FROM AUTHOR]

Summary of main observation and conclusion: The N‐glycans attached to some chloroviruses comprise a hyperbranched core structure without precedent. We are interested in the chemical synthesis of the hexasaccharide attached to ATCV‐1 (Acanthocystis turfacea Chlorella virus 1) for its distinct structure. After exploring four routes, the target hexasaccharide 2 was successfully synthesized for the first time in overall 10% yield over 8 steps from thioglycoside building blocks. This synthetic protocol is characterized by the three‐component one‐pot glycosylation and the regioselective glycosylation reactions. The disclosed synthetic approach to this new type of N‐glycans will facilitate the in‐depth understanding of their biological functions. A highly branched hexasaccharide was successfully synthesized by the three‐component preactivation‐based one‐pot glycosylation and the regioselective glycosylation reactions for the first time. [ABSTRACT FROM AUTHOR]

A stereoselective Koenigs-Knorr glycosylation reaction under the catalysis of urea is described. This method is characterized by urea-mediated hydrogen-bond activation and subsequent glycosylation with glycosyl chlorides or bromides. Excellent yields and high anomeric selectivity can be achieved in most cases. Moreover, the low a-stereoselectivity of glycosylations observed when using perbenzylated glucosyl donors can be greatly improved by the addition of tri-(2,4,6-trimethoxyphenyl) phosphine (TTMPP). [ABSTRACT FROM AUTHOR]

2-Deoxyglycosides, Bromine Radical, Intermolecular Hydroetherification, Photoreaction, Stereoselectivity The rapid constructions of oligosaccharides, 20-mer deoxyglycan, and digoxin are facilitated by a bromide-based hydrogen species through an electron transfer process. Keywords: 2-Deoxyglycosides; Bromine Radical; Intermolecular Hydroetherification; Photoreaction; Stereoselectivity EN 2-Deoxyglycosides Bromine Radical Intermolecular Hydroetherification Photoreaction Stereoselectivity 1 1 1 05/05/22 20220509 NES 220509 B A visible-light-promoted b iterative synthesis of 2-deoxyoligosaccharides is reported by De-Cai Xiong, Xin-Shan Ye, and co-workers in their Research Article (e202114726). [Extracted from the article]

Keywords: 2-Deoxyglycosides; Bromine Radical; Intermolecular Hydroetherification; Photoreaction; Stereoselectivity EN 2-Deoxyglycosides Bromine Radical Intermolecular Hydroetherification Photoreaction Stereoselectivity 1 1 1 05/05/22 20220509 NES 220509 B Sichtbares Licht b vermittelt die iterative Synthese von 2-Desoxyoligosacchariden, über die De-Cai Xiong, Xin-Shan Ye und Mitarbeiter in ihrem Forschungsartikel berichten (e202114726). Innentitelbild: Iterative Synthesis of 2-Deoxyoligosaccharides Enabled by Stereoselective Visible-Light-Promoted Glycosylation (Angew. 2-Deoxyglycosides, Bromine Radical, Intermolecular Hydroetherification, Photoreaction, Stereoselectivity. [Extracted from the article]

Abstract: The repeating GalpNAc-α-(1→4)-GalpNAc unit is part of a series of essential structures that can be found in many important biomolecules such as the glycoproteins and the O-antigenic polysaccharides of clinically important bacterial strains. In this paper, we describe an exclusive α-selective glycosylation reaction, using a 4,6-di-O-tert-butyldimethylsilyl-N-acetyloxazolidinone-protected thioglycoside as the glycosyl donor, under pre-activation conditions, with only half amount of the promoter, providing the product GalpNAc-α-(1→4)-GalpNAc in high isolated yield. This reaction can be also applied to increasing the length of the repeating structure, which is of significant use in further synthesis of branched or linear oligosaccharides. [ABSTRACT FROM AUTHOR]

An efficient preactivation protocol for the highly α-stereo�selective glycosylation of 2-deoxy- and 2,6-dideoxysugars has been developed using acetyl-protected 2-deoxy- and 2,6-dideoxythioglycosides as glycosyl donors. The approach allows a wide range of glycosyl acceptors and donors to be used. [ABSTRACT FROM AUTHOR]

Abstract: A new sialyl donor, N,N-acetyl, benzoyl-O-perbenzoyl-protected p-toluenethiosialoside, was synthesized and its sialylation reaction was investigated. This reaction proceeded in dichloromethane and β anomeric selectivity was achieved when NIS–TfOH was used as promoter. This method may be employed to construct the unnatural β-linked sialosides. [Copyright &y& Elsevier]

3-Butenyloxycarbonyl (Bloc) has been identified as a new hydroxyl protecting group, which can be introduced under mild conditions in high yields and selectively removed by OsO 4 /NaIO 4 /2,6-lutidine in CH 3 CN–H 2 O without affecting most commonly-used protecting groups. Moreover, this new protecting group is inert under glycosylation conditions. [ABSTRACT FROM AUTHOR]

Stereo-controllable glycosylation reactions of 2,3-oxazolidinone protected glucosamine thioglycoside donor with different phenol acceptors based on preactivation protocol, are described. It was found that BF 3 ·Et 2 O worked as α-directing additive, while TTBP acted as β-directing additive. Simply by altering additives, either α-aryl glycosides or β-aryl glycosides were achieved in a stereoselective manner. The additives were also applied to the stereoselective glycosylation reactions of 2,3-oxazolidinone protected galactosamine donor with phenol substrates. [ABSTRACT FROM AUTHOR]

Highlights: [•] o-Methylphenylthioglycosides were used as blocks in preactivation protocol. [•] The aglycon transfer was avoided. [•] The efficiency of glycosyl coupling reactions was enhanced. [•] The thioglycosides were efficiently employed in one-pot oligosaccharide assembly. [ABSTRACT FROM AUTHOR]

A new approach for the synthesis of phenolic glycosides via aromatic O-glycosylation of 1,2-anhydrosugar and aryl boronic acids was disclosed. This method is characterized by the use of aryl boronic acid as the aryl source and produces phenolic glycosides in a stereoselective manner. This reaction provides an alternative approach to the synthesis of phenolic glycosides. It also represents a new application of aryl boronic acids as versatile reagents in organic synthesis. [ABSTRACT FROM AUTHOR]

Abstract: Diverse 2,3-oxazolidinone protected 2-amino-2-deoxy-d-glucose thioglycosides were prepared and studied as glycosyl donors at low temperature by BSM/Tf2O pre-activation protocol before the addition of glycosyl acceptors. The stereochemistry outcomes of a series of glycosylations were investigated. Different stereoselectivities of the coupling reactions were obtained, arising from the different protecting groups in the oxazolidinone donors. 4,6-Di-O-benzyl-N-benzyl-oxazolidinone protected thioglycoside donor 1c underwent glycosylation with general β-anomeric selectivity and the stereoselectivity could be also affected by glycosylation conditions. [Copyright &y& Elsevier]

Chemical O -glycosylation is a key step for the synthesis of sugar-containing molecules such as glycolipids. However, traditional carbohydrate chemistry is characterized by extensive use of protective groups, resulting in laborious manipulations and poor atom economy. Here, we present a protecting-group-free glycosylation strategy employing dibenzyloxy-1,3,5-triazin-2-yl glycosides (DBT-glycosides) as glycosyl donors. The DBT-glycosyl donors could be prepared directly through an alkaline nucleophilic substitution from unprotected sugars in aqueous media. The O -glycosylation of alcohols by using DBT-glycosyl donors has been carried out under mild hydrogenolytic conditions, affording the corresponding alkyl glycosides stereo-selectively in good yields. [Display omitted] • A protecting group-free and stereoselective O -glycosylation method was described. • Glycosyl donors were prepared directly from unprotected sugars under water media. • Glycosylation reaction was performed under mild hydrogenolysis conditions. • Various sugar types (e.g., Glc, Gal, Man, GlcN, GlcNAc, etc) were screened. [ABSTRACT FROM AUTHOR]

The 3-butenyloxycarbonyl group can be introduced into carbohydrates such as (I) under mild conditions. [ABSTRACT FROM AUTHOR]

A new useful method for the synthesis of phenolic glycosides by the reaction of 1,2-anhydrosugars with aryl boronic acids is reported. [ABSTRACT FROM AUTHOR]

2-Pyridyl glycosides have been identified to be powerful glycosyl donors for the preactivation-based oligosaccharide synthesis. By using stoichiometric amount of Tf 2 O, the 2-pyridyl glycosides were pre-activated, which subsequently underwent glycosylation reactions smoothly to produce the coupled products in high yields. Furthermore, the 2-pyridyl glycosides were applied to the efficient oligosaccharide assembly by the preactivation-based one-pot oligosaccharide synthesis protocol. [ABSTRACT FROM AUTHOR]

Review: 174 refs. [ABSTRACT FROM AUTHOR]

Abstract: A new class of pseudoacarviosins with 2,3-anhydro or unsaturated sugar moieties were synthesized efficiently. The designed target disaccharides were constructed by the glycosylation reactions using 2,3-anhydromonosaccharides as glycosyl donors. The glycosylation reactions were carried out in a highly stereoselective manner in most cases, especially when the preactivation protocol was used. The anhydrosugar units of disaccharides were kept intact during the deprotection operations of protective groups. Furthermore, the disaccharides containing anhydrosugar moieties were smoothly converted to the unsaturated disaccharides via the base-promoted rearrangement of sugar epoxides. [Copyright &y& Elsevier]

Abstract: Gb3 and isoGb3 are both biologically important oligosaccharides. A new efficient synthesis of Gb3 and isoGb3 trisaccharide analogues has been achieved by one-pot sequential glycosylation strategy starting from simple monosaccharide building blocks promoted by N-(phenylthio)-ɛ-caprolactam at room temperature. [Copyright &y& Elsevier]

Abstract: Xenotransplantations from pig to human are rapidly rejected because of the interaction between α-Gal epitopes carried by the graft and natural antibodies (anti-Gal antibodies) present in the blood of the recipient. This paper describes a three-component one-pot synthesis of three α-Gal related oligosaccharides with minimal protecting group manipulations in a very short period of time. [Copyright &y& Elsevier]

A stereoselective Koenigs-Knorr glycosylation reaction under the catalysis of urea is described. [ABSTRACT FROM AUTHOR]

An atom economic and environmentally friendly protocol for C-glycosylation of iodoglycals is presented. [ABSTRACT FROM AUTHOR]

Activation of thioglycosides upon UV irradiation followed by cupric triflate oxidation leads to the in situ formation of an oxacarbenium ion which is able to undergo glycosylation reactions with a wide variety of substrates such as sugars, amino acids, terpenes, and sterols. [ABSTRACT FROM AUTHOR]