Glycosylation with Disarmed Glycosyl Bromides Promoted by Iodonium Ions

Iodonium ions have been developed for activating glycosyl bromides in the coupling to glycosyl acceptors. The iodonium ions are generated from N‐iodosuccinimide and a protic acid such as camphorsulfonic acid or triflic acid, where the latter gives the most reactive promoter system. The couplings occur with the release of iodine monobromide, and the best results are obtained with benzoylated glycosyl donors and acceptors. In this way, disarmed glycosyl bromides can serve as glycosyl donors without the use of heavy‐metal salts. N‐Iodosuccinimide and triflic acid have been developed as a promoter system for activating disarmed glycosyl bromides. Glycosylations with these donors can then be performed with a more benign promoter instead of the commonly employed silver and mercury salts.