Communication
Mechanism of 4,6-O-Benzylidene-Directed β-Mannosylation as Determined by α-Deuterium Kinetic Isotope Effects†
David Crich Prof. Dr.,
N. Susantha Chandrasekera,
David Crich Prof. Dr.
Department of Chemistry, University of Illinois at Chicago, 845 West Taylor Street, Chicago, IL 60607-7061, USA, Fax: (+1) 312-996-4439
Search for more papers by this authorN. Susantha Chandrasekera
Department of Chemistry, University of Illinois at Chicago, 845 West Taylor Street, Chicago, IL 60607-7061, USA, Fax: (+1) 312-996-4439
Search for more papers by this authorDavid Crich Prof. Dr.,
N. Susantha Chandrasekera,
David Crich Prof. Dr.
Department of Chemistry, University of Illinois at Chicago, 845 West Taylor Street, Chicago, IL 60607-7061, USA, Fax: (+1) 312-996-4439
Search for more papers by this authorN. Susantha Chandrasekera
Department of Chemistry, University of Illinois at Chicago, 845 West Taylor Street, Chicago, IL 60607-7061, USA, Fax: (+1) 312-996-4439
Search for more papers by this author†
We thank the National Institutes of Health (GM 62160) for support of our work in this area
Graphical Abstract
Considerable oxacarbenium ion character may be in the transition state of a highly β-selective mannosylation reaction that proceeds via an α-mannosyl triflate. An α-deuterium kinetic isotope effect of 1.2 was measured at −78 °C (≡1.1 at 25 °C). This information may be interpreted in terms of a stereoselective trapping of a transient contact ion pair or, alternatively, as representative of an “exploded” transition state (see scheme).
Supporting Information
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