Glycosyl fluorides from n-pentenyl-related glycosyl donors - Application to glycosylation strategies

n-Pentenyl glycosides (NPGs) and n-pentenyl orthoesters (NPOEs) have been transformed into glycosyl fluorides by a variety of methods. In the case of NPGs, Barluenga's reagent, bis(pyridinium) iodonium(I) tetrafluoroborate (IPy2BF4), gives good yields of glycosyl fluorides when HF-pyridine complex is used as an additional fluoride source. NPOEs can be activated either by a combination of electrophilic iodonium (Barluenga's reagent) and HBF4 or by the action of HF-pyridine complex. The ensuing glycosyl fluorides form a semiorthogonal pair of glycosyl donors when confronted with NPGs.