A fluorinated N-acetylglucosamine analog in which the C4 hydroxyl is replaced by a fluorine. Fluorinated GlcNAc analogs are valuable probes for studying GlcNAc-processing enzymes (O-GlcNAc transferase / OGA, hexosaminidases, glycosyltransferases) and as metabolic inhibitors of N-glycan, O-GlcNAc, and glycosaminoglycan biosynthesis. The carbon-fluorine bond is stable, isosteric with the native hydroxyl, and provides a handle for ¹⁹F NMR studies of glycan-protein interactions.