Browsing by Author "Chao, Chin-Sheng"

Now showing 1 - 11 of 11

A mild and general method for preparation of alpha-glycosyl chlorides
(2009-08-05)
Chang, Chih-Wei
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Chang, Shih-Sheng
;
Chao, Chin-Sheng
;
Mong, Kwok-Kong T.
;
應用化學系
A mild and efficient chlorination method for production of glycosyl chlorides is first described which employs inexpensive trichlorotriazine (TCT) and DMF as a chlorination reagent and is compatible with typical acid-labile hydroxyl protecting functions. The scope and limitations, reaction mechanism and its application in the sequential glycosylations are discussed. (C) 2009 Elsevier Ltd. All rights reserved.
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.
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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.
Joined use of oxazolidinone and desymmetric amino protection: a new strategy for protection of glucosamine
(2010-04-07)
Lin, Shih-Che
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Chao, Chin-Sheng
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Chang, Chiu-Ching
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Mong, Kwok-Kong T.
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應用化學系
Joined use of N-benzyl oxazolidinone and N-benzyl-N-benzyloxycarbonyl (N-BnCbz) desymmetric amino-protecting function is reported. The new synthetic approach enables the facile preparation of type I and type 2 LacNAc disaccharides in satisfactory yields. One-pot deprotection of N-BnCbz and O-benzyl ether is achieved by hydrogenolysis under mild conditions. (C) 2010 Elsevier Ltd. All rights reserved.
Low-Concentration 1,2-trans beta-Selective Glycosylation Strategy and Its Applications in Oligosaccharide Synthesis
(2009)
Chao, Chin-Sheng
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Li, Chen-Wei
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Chen, Min-Chun
;
Chang, Shih-Sheng
;
Mong, Kwok-Kong Tony
This study develops an operationally easy, efficient, and general 1,2-trans beta-selective glycosylation reaction that proceeds in the absence of a C2 acyl function. This process employs chemically stable thioglycosyl donors and low substrate concentrations to achieve excellent beta-selectivities in glycosylation reactions. This method is widely applicable to a range of glycosylsubstrates irrespective of their structures and hydroxyl-protecting functions. This low-concentration 1,2-trans beta-selective glycosylation in carbohydrate chemistry removes the restriction of using highly reactive thioglycosides to construct 1,2-trans beta-glycosidic bonds. This is beneficial to the design of new strategies for oligosaccharide synthesis, as illustrated in the preparation of the biologically relevant beta-(1 -> 6)-glucan trisaccharide, beta-linked Gb(3) and isoGb(3) derivatives.
Neighboring-Group Participation by C-2 Ether Functions in Glycosylations Directed by Nitrile Solvents
(2011-10-01)
Chao, Chin-Sheng
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Lin, Ching-Yu
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Mulani, Shaheen
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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.
Online monitoring of chemical reactions by contactless atmospheric pressure ionization mass spectrometry
(2012-05-01)
Hsieh, Cheng-Huan
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Chao, Chin-Sheng
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Mong, Kwok-Kong Tony
;
Chen, Yu-Chie
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應用化學系
Solvent Participation in a One-Pot Glycosylation Strategy (SPOG)
(2011-04-18)
Chao, Chin-Sheng
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Yen, Yu-Fang
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Hung, Wei-Cheng
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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.
Tandem One-Pot Acetalation-Acetylation for Direct Access to Differentially Protected Thioglycosides and O-Glycosides with p-Toluenesulfonic Acid
(2009-03-03)
Mong, Kwok-Kong Tony
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Chao, Chin-Sheng
;
Chen, Min-Chun
;
Lin, Chun-Wei
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應用化學系
A new tandem one-pot acetalation-acetylation procedure is reported which streamlines routine protecting-group manipulation of carbohydrate molecules in production of differentially protected 0- and thioglycosides. This new procedure eliminates the use of highly toxic pyridine, and p-toluenesulfonic acid is employed as catalyst for acetalation and acetylation. Synthetic utility of the new procedure is demonstrated in the expeditious preparation of differentially protected glycosides from a wide variety of carbohydrate substrates including unprotected O-glycosides, thioglycosides, and N-acetyl neuraminic acid ester.
Tuning Reactivity of Glycosyl Imidinium Intermediate for 2-Azido-2-deoxyglycosyl Donors in alpha-Glycosidic Bond Formation
(2013-10-18)
Ingle, Arun B.
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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.
Ultrasonication-assisted spray ionization mass spectrometry for on-line monitoring of organic reactions
(2010)
Chen, Tsung-Yi
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Chao, Chin-Sheng
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Mong, Kwok-Kong Tony
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Chen, Yu-Chie
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應用化學系
A straightforward on-line monitoring of organic reactions by ultrasonication-assisted spray ionization mass spectrometry (UASI MS) is demonstrated in this work.
Versatile acetylation of carbohydrate substrates with bench-top sulfonic acids and application to one-pot syntheses of peracetylated thioglycosides
(2008-04-07)
Chao, Chin-Sheng
;
Chen, Min-Chun
;
Lin, Shih-Che
;
Mong, Kwok-Kong T.
;
應用化學系
Inexpensive and readily available sulfonic acids, p-toluenesulfonic acid, and sulfuric acid are versatile and efficient catalysts for the peracetylation of a broad spectrum of carbohydrate substrates in good yield and in a practical time frame. Three appealing features in sulfonic acid-catalyzed acetylation of free sugars were explored including (1) suppression of furanosyl acetate formation for D-galactose and L-fucose; (2) high yielding chemoselective acetylation of sialic acid under appropriate conditions; and (3) peracetylation of amino sugars with different amino protecting functions. Simple one-pot two step acetylation-thioglycosidation methods for the expeditious synthesis of p-tolyl per-O-acetyl thioglycosides were also delineated. (C) 2008 Elsevier Ltd. All rights reserved.