Although conformational preferences of neutral six-memberedring
systems are dominated by steric effects,1 recent computational
studies suggest that electronic effects exert a profound influence
on the conformations of six-membered-ring oxocarbenium ions.
In the process of analyzing rates of glycoside hydrolysis, Bowen
and co-workers reported molecular mechanics calculations indicating
that hydroxyl groups at C-4 and C-3 of a six-membered
oxocarbenium ion2 assume pseudoaxial positions in the half-chair
conformation (eq 1).3,4 The pseudoaxial preference has been