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Direct Experimental Evidence for the High Chemical Reactivity of alpha- and beta-Xylopyranosides Adopting a (2,5)B Conformation in Glycosyl Transfer

AuthorsAmorim, Luis; Marcelo, Filipa ; Rousseau, Cyril; Nieto, Lidia ; Jiménez-Barbero, Jesús ; Rauter, Amélia Pilar; Marrot, Jérôme; Sollogoub, Matthie; Bols, Mikael; Blériot, Yves
KeywordsAcid-Catalyzed Hydrolysis
Constrained Glocupyranosides
Glycosidase Inhibitors
Enzyme Intermediate
Oxacarbenium Ions
Issue DateJun-2011
CitationChemistry-A European Journal 17(26):7345-7356(2011)
AbstractThe effect of a (2,5)B boat conformation on xyloside reactivity has been investigated by studying the hydrolysis and glycosylation of a series of synthetic xyloside analogues based on a 2-oxabicyclo[2.2.2] octane framework, which forces the xylose analogue to adopt a (2,5)B conformation. The locked beta-xylosides were found to hydrolyze 100-1200 times faster than methyl beta-D-xylopyranoside, whereas the locked alpha-xylosides hydrolyzed up to 2 x 10(4) times faster than methyl alpha-D-xylopyranoside. A significant rate enhancement was also observed for the glycosylation reaction. The high reactivity of these conformers can be related to the imposition of a (2,5)B conformation, which ap-proximates a transition state (TS) boat conformation. In this way, the energy penalty required to go from the chair to the TS conformation is already paid. These results parallel and support the observation that the GH-11 xylanase family force their substrate to adopt a (2,5)B conformation to achieve highly efficient enzymatic glycosidic bond hydrolysis.
Description12 páginas, 1 figura -- Págs nrs. : 7345-7356
Publisher version (URL)http://dx.doi.org/10.1002/chem.201003251
Appears in Collections:(CIB) Artículos
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