Mechanism of 4,6‐O‐Benzylidene‐Directed β‐Mannosylation as Determined by α‐Deuterium Kinetic Isotope Effects

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 for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2002/2004/z53688_s.pdf or from the author. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.