Browsing by Author "Ghosh, Bhaswati"

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In situ formation of beta-glycosyl imidinium triflate from participating thioglycosyl donors: elaboration to disarmed-armed iterative glycosylation
(2012)
Lin, Yu Hsien
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Ghosh, Bhaswati
;
Mong, Kwok-Kong Tony
;
應用化學系
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Department of Applied Chemistry
beta-Glycosyl imidinium triflate is generated from participating thioglycoside donors for disarmed-armed iterative glycosylations and one-pot oligosaccharide synthesis.
Photoluminescent Gold Nanoclusters as Sensing Probes for Uropathogenic Escherichia coli
(2013-03-15)
Chan, Po-Han
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Ghosh, Bhaswati
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Lai, Hong-Zheng
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Peng, Hwei-Ling
;
Mong, Kwok Kong Tony
Glycan-bound nanoprobes have been demonstrated as suitable sensing probes for bacteria containing glycan binding sites. In this study, we demonstrated a facile approach for generating glycan-bound gold nanoclusters (AuNCs). The generated AuNCs were used as sensing probes for corresponding target bacteria. Mannose-capped AuNCs (AuNCs@Mann) were generated and used as the model sensors for target bacteria. A one-step synthesis approach was employed to generate AuNCs@Mann. In this approach, an aqueous solution of tetrachloroauric acid and mannoside that functionized with a thiol group (Mann-SH) was stirred at room temperature for 48 h. The mannoside functions as reducing and capping agent. The size of the generated AuNCs@Mann is 1.95 +/- 0.27 nm, whereas the AuNCs with red photoluminescence have a maximum emission wavelength of similar to 630 nm (lambda(excitation) = 375 nm). The synthesis of the AuNCs@Mann was accelerated by microwave heating, which enabled the synthesis of the AuNCs@Mann to complete within 1 h. The generated AuNCs@Mann are capable of selectively binding to the urinary tract infection isolate Escherichia coli J96 containing the mannose binding protein FimH expressed on the type 1 pili. On the basis of the naked eye observation, the limit of detection of the sensing approach is as low as similar to 2 x 10(6) cells/mL.
Synthesis of Oligomeric Mannosides and Their Structure-Binding Relationship with Concanavalin A
(2014-07-01)
Li, Chen-Wei
;
Hon, Kai-Wei
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Ghosh, Bhaswati
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Li, Po-Han
;
Lin, Hsien-Ya
Small glycodendrimers with a-mannosyl ligands were synthesized by using copper-catalyzed azide-alkyne coupling chemistry and some of these molecules were used as multivalent ligands to study the induction of concanavalin A (Con A) precipitation. The results showed that the monovalent mannose ligand could induce the precipitation of Con A. This unexpected finding initiated a series of studies to characterize the molecular basis of the ligand-lectin interaction. The atypical precipitation is found to be specific to the mannose, fluorescein moiety (FITC), and Con A. Apparently the mannose ligand binds to Con A through hydrogen-bonding interactions, whereas the binding of FITC is mediated by hydrophobic forces.
Total Synthesis of a Glycoglycerolipid from Meiothermus taiwanensis through a One-Pot Glycosylation Reaction and Exploration of its Immunological Properties
(2013-12-01)
Ghosh, Bhaswati
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Lai, Yen-Hsun
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Shih, Yu-Yin
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Pradhan, Tapan Kumar
;
Lin, Chun-Hung
The total synthesis of a glycoglycerolipid isolate of Meiothermus taiwanensis and its truncated structural analogues is reported. Our synthesis employed DMF-modulated and low-concentration glycosylation reactions for the construction of - and -glycosidic bonds in the absence of participating protecting groups. Further simplification of the synthesis was achieved by employing a low-concentration one-pot glycosylation procedure. Preliminary immunological studies showed that one of the truncated structural analogues suppressed the cytokine production of THP-1 monocytes.
Unusually Stable Picoloyl-Protected Trimethylsilyl Glycosides for Nonsymmetrical 1,1-Glycosylation and Synthesis of 1,1-Disaccharides with Diverse Configurations
(2017-05-01)
Lu, Yen-Chu Luke
;
Ghosh, Bhaswati
;
Mong, Kwok-Kong Tony
;
應用化學系
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Department of Applied Chemistry
Nonsymmetrical 1,1-disaccharides and related derivatives constitute structural components in various glycolipids and natural products. Some of these compounds have been shown to exhibit appealing biological properties. We report a direct yet stereoselective 1,1-glycosylation strategy for the synthesis of nonsymmetrical 1,1-disaccharides with diverse configurations and sugar components. The strategy is based on the joined forces of a new class of configurationally stable glycoside acceptors and stereodirecting thioglycoside donors. The new glycoside acceptors feature a picoloyl (Pico) protecting group at the remote C4/C3 position that confers unusual stability on TMS glycosides under acidic conditions.