Glycosyl haloacetimidates: Synthesis, kinetics and glycosylation properties.

A method for synthesizing glycosyl haloacetimidates in a two-chamber reaction vessel is used to access new glycosyl haloacetimidates. Simple haloacetamides are transformed into the corresponding gaseous halonitriles in one chamber and these react with the hemiacetal in the other chamber. In this paper the properties of the new glycosyl haloacetimidates are studied with a focus on glycosylation properties. Especially the solvolysis reactions in neat simple alcohols are studied and compared with seminal work by Schmidt and coworkers. For the α-anomeric acetimidates inversion is seen with less bulky acceptors while increasing steric bulk increases the amount of α-product. For the β-anomeric acetimidates inversion is seen in all cases. Glycosylation screening of five model glycosyl acceptors reveals that the glycosyl haloacetimidates are glycosylating agents comparable with the Schmidt donor.