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Tsun-Yi Chiang

Bio: Tsun-Yi Chiang is an academic researcher from Academia Sinica. The author has contributed to research in topics: Glycosylation & Carbohydrate synthesis. The author has an hindex of 1, co-authored 2 publications receiving 6 citations.

Papers
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Journal ArticleDOI
TL;DR: A multifaceted experimental approach is reported that reveals the behaviors of side reactions, such as the intermolecular thioaglycon transformation and N-glycosyl succinimides, via the glycosyl intermediate, which lowers its yield and limits its efficiency.
Abstract: The glycosylation reaction, which is key for the studies on glycoscience, is challenging due to its complexity and intrinsic side reactions. Thioglycoside is one of the most widely used glycosyl donors in the synthesis of complex oligosaccharides. However, one of the challenges is its side reactions, which lower its yield and limits its efficiency, thereby requiring considerable effort in the optimization process. Herein, we reported a multifaceted experimental approach that reveals the behaviors of side reactions, such as the intermolecular thioaglycon transformation and N-glycosyl succinimides, via the glycosyl intermediate. Our mechanistic proposal was supported by low temperature NMR studies that can further be mapped by utilizing relative reactivity values. Accordingly, we also presented our findings to suppress the generation of side products in solving this particular problem for achieving high-yield glycosylation reactions.

16 citations

Journal ArticleDOI
TL;DR: In this paper, a multifunctional O-phenyl thiocarbonyl (O(C═S)OPh) group was introduced in glycosylation reactions.

6 citations


Cited by
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Journal ArticleDOI
TL;DR: A database of acceptor nucleophilic constants (Aka) was developed to quantify the nucleophilicity of hydroxyl groups in glycosylation influenced by the steric, electronic and structural effects, providing a connection between experiments and computer algorithms as discussed by the authors.
Abstract: The stereoselectivity and yield in glycosylation reactions are paramount but unpredictable. We have developed a database of acceptor nucleophilic constants (Aka) to quantify the nucleophilicity of hydroxyl groups in glycosylation influenced by the steric, electronic and structural effects, providing a connection between experiments and computer algorithms. The subtle reactivity differences among the hydroxyl groups on various carbohydrate molecules can be defined by Aka, which is easily accessible by a simple and convenient automation system to assure high reproducibility and accuracy. A diverse range of glycosylation donors and acceptors with well-defined reactivity and promoters were organized and processed by the designed software program "GlycoComputer" for prediction of glycosylation reactions without involving sophisticated computational processing. The importance of Aka was further verified by random forest algorithm, and the applicability was tested by the synthesis of a Lewis A skeleton to show that the stereoselectivity and yield can be accurately estimated.

33 citations

Journal ArticleDOI
TL;DR: Intramolecular interactions, identified by molecular dynamics simulations and NMR analysis, underscore the importance of the chitosan amino group for the stabilization of specific geometries.
Abstract: Chitin, a polymer composed of β(1-4)-linked N-acetyl-glucosamine monomers, and its partially deacetylated analogue chitosan, are abundant biopolymers with outstanding mechanical as well as elastic properties. Their degradation products, chitooligosaccharides (COS), can trigger the innate immune response in humans and plants. Both material and biological properties are dependent on polymer length, acetylation, as well as the pH. Without well-defined samples, a complete molecular description of these factors is still missing. Automated glycan assembly (AGA) enabled rapid access to synthetic well-defined COS. Chitin-cellulose hybrid oligomers were prepared as important tools for a systematic structural analysis. Intramolecular interactions, identified by molecular dynamics simulations and NMR analysis, underscore the importance of the chitosan amino group for the stabilization of specific geometries.

13 citations

Journal ArticleDOI
TL;DR: Isothermal glycosylation below the activation temperature halved the equivalents of building block required in comparison to the standard 'ramp' regime used in solution- and solid-phase oligosaccharide synthesis to-date.
Abstract: Abstract Glycosidic bond formation is a continual challenge for practitioners. Aiming to enhance the reproducibility and efficiency of oligosaccharide synthesis, we studied the relationship between glycosyl donor activation and reaction temperature. A novel semi‐automated assay revealed diverse responses of members of a panel of thioglycosides to activation at various temperatures. The patterns of protecting groups and the thiol aglycon combine to cause remarkable differences in temperature sensitivity among glycosyl donor building blocks. We introduce the concept of donor activation temperature to capture experimental insights, reasoning that glycosylations performed below this reference temperature evade deleterious side reactions. Activation temperatures enable a simplified temperature treatment and facilitate optimization of glycosyl donor usage. Isothermal glycosylation below the activation temperature halved the equivalents of building block required in comparison to the standard “ramp” regime used in solution‐ and solid‐phase oligosaccharide synthesis to‐date.

10 citations

Journal ArticleDOI
10 Mar 2022
TL;DR: It is reported that N-phenyltrifluoroacetimidoyl (PTFAI), a well-known leaving group for catalytic glycosylation, can act as a stereodirecting group for the challenging 1,2-cis α-glycosylating of trisaccharide heparins.
Abstract: The anomeric configuration can greatly affect the biological functions and activities of carbohydrates. Herein, we report that N-phenyltrifluoroacetimidoyl (PTFAI), a well-known leaving group for catalytic glycosylation, can act as a stereodirecting group for the challenging 1,2-cis α-glycosylation. Utilizing rapidly accessible 1,6-di-OPTFAI glycosyl donors, TMSOTf-catalyzed glycosylation occurred with excellent α-selectivity and broad substrate scope, and the remaining 6-OPTFAI group can be cleaved chemoselectively. The remote participation of 6-OPTFAI is supported by the first characterization of the crucial 1,6-bridged bicyclic oxazepinium ion intermediates by low-temperature NMR spectroscopy. These cations were found to be relatively stable and mainly responsible for the present stereoselectivities. Further application is highlighted in glycosylation reactions toward trisaccharide heparins as well as the convergent synthesis of chacotriose derivatives using a bulky 2,4-di-O-glycosylated donor.

8 citations

Journal ArticleDOI
TL;DR: The same sulfonate system can be used for the selective synthesis of α-glycosides containing the allo-configured 2-deoxy sugar digitoxose and optimal selectivity is obtained through matching the donor with the appropriate arylsulfonyl chloride promoter.

6 citations