Two isosteric fluorinated derivatives of the powerful glucosidase inhibitors, 1-deoxynojirimycin and 2,5-dideoxy-2,5-imino-d-mannitol: Syntheses and glucosidase-inhibitory activities of 1,2,5-trideoxy-2-fluoro-1,5-imino-d-glucitol and of 1,2,5-trideoxy-1-

1,2,5-Trideoxy-2-fluoro-1,5-imino-d-glucitol, the 2-deoxyfluoro derivative of 1-deoxynojirimycin, as well as 1,2,5-trideoxy-1-fluoro-2,5-imino-d-mannitol and 2,5-dideoxy-2,5-imino-1-O-methyl-d-mannitol, two new analogues of the natural product and powerful glucosidase inhibitor 2,5-dideoxy-2,5-imino-d-mannitol, were synthesised featuring glucose isomerase-catalysed aldose-ketose interconversion reactions as the key steps of the syntheses. Results of inhibition studies conducted with these compounds and previously obtained deoxyfluoro derivatives of 1-deoxynojirimycin, employing glucosidases from various sources, showed that the replacement of a hydroxyl function by fluorine caused an impairment of the inhibitory potency. This effect was smallest for the hydroxyl group at C-6 up to four orders of magnitude larger for replacements at C-2 and C-3. Title compounds were synthesized by chemical and chemo-enzymatic routes.