The reaction of D-glucal and its derivatives with the electrophilicN-F-fluorination reagents F-TEDA tetrafluoroborate and triflate was studied by means of19F NMR spectroscopy. In all cases mixtures of 2-deoxy-2-fluoro-D-gluco- and -D-mannopyranose derivatives were formed, the ratio of which was dependent on the nature of theO-protecting groups. Concerning the products arising from the direct addition of reagents across the double bond, the D-gluco-configured compounds (13-20) generally showed higher hydrolysis rates than their D-manno-counterparts (21-28). Product separation was only achieved when single anomers (e.g., 2,4-dinitrophenyl glycosides29e/37eand disaccharidic fluorides35d/43d) or per-O-acetates (e.g.29f/37f) were formed.