The efficient synthesis of enantiomeric pairs of iminosugars including 1,4-dideoxy-1,4-imino-D-arabinitol (DAB) and 1,4-dideoxy-1,4-imino-L-arabinitol (LAB) analogues with an amidine, hydrazide, hydrazide imide, or amide oxime moiety is described. The preparation of DAB and LAB analogues commenced from L-xylose and D-xylose, respectively. Title iminosugars were tested against a panel of glycosidases with therapeutic relevance, revealing an enhanced activity of DAB analogues in comparison with the LAB analogues. In particular, the D-arabino-configured amidine behaved as a potent (sub micromolar range) and selective inhibitor of α-mannosidase.