Fluorinated and conformationally fixed derivatives of L-homoDMDP, i.e., 2,5-dideoxy-2,5-imino-DL-glycero-L-manno-heptitol, have been synthesized from d-xylose-derived cyclic nitrone 10 with oxazolidinone 19 or 28 and oxazinanone 22 or 32 as key intermediates. An evaluation of glycosidase inhibition showed replacement of the C-6 hydroxyl groups with fluoride in L-homoDMDP and its C-6 epimer did not have a significant influence on α-glucosidase inhibition by these iminosugars, while replacement of an amino group with a cyclic carbamate group in most conformationally fixed derivatives led to a sharp decrease in the level of glycosidase inhibition, revealing the importance of the free amino group in interaction of enzymes with these molecules.