Browsing by Author "Hung, Wei-Cheng"

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(2-Ketulosonyl)onate 2,3-O-thionocarbonate donors for the synthesis of KO and KDO alpha-glycosides and a one-pot glycosylation method for 2-keto acid donors
(2020-08-21)
Mong, Kwok-Kong Tony
;
Pradhan, Tapan Kumar
;
Chiu, Cheng-Hsin
;
Hung, Wei-Cheng
;
Chen, Chao-Ju
We report a short synthetic strategy for direct preparation of (2-ketulosonyl)onate donors. These donors feature a cyclic thionocarbonate group at the C2 and C3 positions, which plays a multitude of chemical roles. It protects the C2 and C3 hydroxyls during building block preparation. In glycosylation, the thionocarbonate can be activated by a sulfenylating promoter and serves as a leaving group. Because of its beta-configuration, it also plays the role of a stereo-directing group during the formation of the alpha-glycosidic bond. In addition, the thionocarbonate donors can couple with thioglycoside acceptors. This orthogonal property was used for the development of the first one-pot glycosylation method for 2-keto acid sugars.
Application of 2-Azido-2-deoxythioglycosides for beta-Glycoside Formation and Oligosaccharide Synthesis
(2012-05-01)
Mong, Kwok-Kong Tony
;
Yen, Yu-Fang
;
Hung, Wei-Cheng
;
Lai, Yen-Hsun
;
Chen, Jiun-Han
Most natural 2-acetamido-2-deoxyglycosides exist in a 1,2-trans-beta-glycosidic configuration. This study investigated the use of 2-azido-2-deoxythioglycosides for 1,2-trans-beta-glycosidic bond formation under low-concentration glycosylation conditions. Further application of the 2-azido-2-deoxythioglycosyl substrates for one-pot oligosaccharide synthesis was demonstrated in the synthesis of protected beta-(1?6)-N-acetylglucosamine trimer, core-6serine conjugate, and F1a serine conjugate.
Chemical Synthesis of the O-Antigen Repeating Unit of Escherichia coli O86 by an N-Formylmorpholine-Modulated One-Pot Glycosylation Strategy
(2014-08-01)
Ingle, Arun B.
;
Chao, Chin-Sheng
;
Hung, Wei-Cheng
;
Mong, Kwok-Kong Tony
;
應用化學系
The synthesis of the O-antigen pentasaccharide repeating unit of the cell wall of Gram-negative bacteria Escherichia coli O86 is reported. The synthesis features the use of an N-formylmorpholine (NFM)-modulated glycosylation method for the construction of 1,2-cis alpha-glycosidic linkages and an [1+1+2] iterative one-pot alpha-glycosylation strategy to accelerate the assembly of the tetrasaccharide backbone.
Modulating glycosylation with exogenous nucleophiles: an overview
(2014)
Mulani, Shaheen K.
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Hung, Wei-Cheng
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Ingle, Arun B.
;
Shiau, Kai-Sheng
;
Mong, Kwok-Kong Tony
The major challenge in carbohydrate synthesis is stereochemical control of glycosidic bond formation. Different glycosylation methods have been developed that are based on the modulation effect of external nucleophiles. This review highlights the development, synthetic application, challenges and outlook of the modulated glycosylation methods.
Neighboring-Group Participation by C-2 Ether Functions in Glycosylations Directed by Nitrile Solvents
(2011-10-01)
Chao, Chin-Sheng
;
Lin, Ching-Yu
;
Mulani, Shaheen
;
Hung, Wei-Cheng
;
Mong, Kwok-kong Tony
Ether-protecting functions at C-2 hydroxy groups have been found to play participating roles in glycosylations when the reactions are conducted in nitrile solvent mixtures. The participation mechanism is based on intramolecular interaction between the lone electron pair of the oxygen atom of the C-2 ether function and the nitrile molecule when they are positioned in a cis configuration. A 1,2-cis glycosyl oxazolinium intermediate is formed. This participation, in conjunction with the anomeric effect of the glycosyl donor, confers high 1,2-trans selectivities on glycosylations. Further application of this concept has led to efficient preparations of alpha-(1 -> 5)-arabinan oligomers.
Solvent Participation in a One-Pot Glycosylation Strategy (SPOG)
(2011-04-18)
Chao, Chin-Sheng
;
Yen, Yu-Fang
;
Hung, Wei-Cheng
;
Mong, Kwok-Kong Tony
;
應用化學系
Solvent participation in a one-pot glycosylation strategy (SPOG) was developed on the basis of the low concentration beta-selective glycosylation method. This strategy enables the production of a beta-glycosidic bond in a one-pot oligosaccharide synthesis without or with minimal use of any C-2 participating function.
Tuning Reactivity of Glycosyl Imidinium Intermediate for 2-Azido-2-deoxyglycosyl Donors in alpha-Glycosidic Bond Formation
(2013-10-18)
Ingle, Arun B.
;
Chao, Chin-Sheng
;
Hung, Wei-Cheng
;
Mong, Kwok-Kong Tony
;
應用化學系
The chemical properties of nucleophile additives were investigated in a modulated glycosylation context. N-Formylmorpholine (NFM) was found to be an effective modulator for glycosylation with less reactive 2-azido-2-deoxythioglucosyl and thiogalactosyl donors.