C7 Epimerization of Benzylidene-Protected β-d-Idopyranosides Brings Structural Insights into Idose Conformational
Maude Cloutier1, Serge Lavoie2, Charles Gauthier1,2
1Unité Mixte de Recherche INRS-UQAC, Centre Armand-Frappier Santé Biotechnologie, Institut National de la Recherche Scientifique (INRS), 555, boulevard de l'Université, Chicoutimi, Québec, Canada G7H 2B1.
Abstract:
Idose is unique among other aldohexoses because of its high conformational flexibility in solution. We herein show that benzylidene acetal-protected 3-O-acyl-β-d-idopyranosides undergo Lewis acid-catalyzed C7 epimerization with concomitant 4C1 to 1C4 ring inversion. The reaction conditions and structural parameters for this transformation to occur have been thoroughly investigated through an extensive glycosylation study combined with NMR analyses, X-ray diffraction, and quantum molecular modeling. In addition to reporting a direct, β-stereoselective idosylation approach, our work brings fundamental structural insights into the conformational flexibility of idose.
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