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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]

An oligosaccharides library of small tri- and tetrasaccharides is prepared by one-pot sequential glycosylation strategies using thioglycosides as glycosylation reagents. The methodology facilitates rapid assembly of 33 linear or branched protected oligosaccharides.

O -GlcNAcylation is a post-translational modification that links metabolism with signal transduction. High O -GlcNAcylation appears to be a general characteristic of cancer cells. It promotes the invasion, metastasis, proliferation and survival of tumor cells, and alters many metabolic pathways. Glycogen metabolism increases in a wide variety of tumors, suggesting that it is an important aspect of cancer pathophysiology. Herein we focused on the O -GlcNAcylation of liver glycogen phosphorylase (PYGL)—an important catabolism enzyme in the glycogen metabolism pathway. PYGL expressed in both HEK 293T and HCT116 was modified by O -GlcNAc. And both PYGL O -GlcNAcylation and phosphorylation of Ser15 (pSer15) were decreased under glucose and insulin, whereas increased under glucagon and Na2S2O4 (hypoxia) conditions. Then, we identified the major O -GlcNAcylation site to be Ser430, and demonstrated that pSer15 and Ser430 O -GlcNAcylation were mutually reinforced. Lastly, we found that Ser430 O -GlcNAcylation was fundamental for PYGL activity. Thus, O -GlcNAcylation of PYGL positively regulated pSer15 and therefore its enzymatic activity. Our results provided another molecular insight into the intricate post-translational regulation network of PYGL. [ABSTRACT FROM AUTHOR]

A novel method for the synthesis of unsymmetrically 3,4-disubstituted thiophenes was developed based on the intermolecular thiazole-alkyne Diels-Alder reactions involving 3,4-bis(trimethylsilyl)thiophene. The synthetic strategy was characterized by the formation of the [2+2]- and [4+2]-cycloaddition adducts of 3,4-didehydrothiophene via 1,3-dipolar cycloadditions. Furthermore, the synthetic process was characterized by 3,4-bromothiophene modification and intermolecular thiazole-alkyne Diels-Alder reactions with 3,4-bis(trimethylsilyl)thiophene.

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]

Two photoreactions for the synthesis of 1- and 2-deoxysugars from thioglycosides were developed. In the presence of Hantzsch ester as an additive, a wide range of 1-deoxysugars were synthesized in moderate to excellent yields under irradiation with UV light without an exogenous photosensitizer. On the other hand, the utilization of 2,4,6-tri-tert-butylpyrimidine (TTBP) as the additive furnished a variety of 2-deoxysugars as the main products from their corresponding thioglycosides. The reported methodology has a broad substrate scope and high functional group tolerance and is scalable to gram-scale reaction. [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]