Ketonitrone 8 was prepared fromd-fructose as an inexpensive starting material and was used in a stereoselective synthesis of 1-deoxymannojirimycin (DMJ, 4), of its previously unknown N-hydroxy analogue 15, and of the polyhydroxylated ketonitrone 14. The latter were assayed as potential glycosidase inhibitors on a panel of 13 selected purified enzymes. Disappointingly, the polyhydroxylated nitrone