O ‐(1‐Phenyl‐1 H ‐tetrazol‐5‐yl) Glycosides: Alternative synthesis and transformation into glycosyl fluorides

A number of new glycosyl donors, O ‐(1‐phenyl‐1 H ‐tetrazol‐5‐yl) glycosides, are prepared from the corresponding hemiacetals, commercially available 5‐chloro‐1‐phenyl‐1 H ‐tetrazole ( 2 ), and tetrabutylammonium fluoride (Bu 4 NF) in either THF or DMF. The mild reaction conditions are compatible with a variety of protecting groups. The glycosyl donors are treated with hydrogen fluoride‐pyridine complex (HF·py) to rapidly provide glycosyl fluorides in good‐to‐excellent yields, apparently by a (single or double) S N 2 mechanism as studied by both 1 H‐ and 19 F‐NMR spectroscopy. Under acidic conditions, glycosyl fluorides equilibrate partially or completely, equilibration requiring a large excess of HF · py.