A propos of glycosyl cations and the mechanism of chemical glycosylation; the current state of the art

An overview of recent advances in glycosylation with particular emphasis on mechanism is presented. The mounting evidence for both the existence of glycosyl oxocarbenium ions as fleeting intermediates in some reactions, and the crucial role of the associated counterion in others is discussed. The extremes of the S(N)1 and S(N)2 manifolds for the glycosylation reaction are bridged by a continuum of mechanisms in which it appears likely that most examples are located. (C) 2014 Elsevier Ltd. All rights reserved.