novel heptitol analogues of mannofuranose and their syntheses from δ - lactones of heptonic acids are disclosed . the novel heptitols are 2 , 5 - dideoxy - 2 , 5 - imino - d - glycero - d - talo - heptitol and 1 - amino - 2 , 5 - anhydro - 1 - deoxy - d - glycero - d - talo - heptitol . these novel heptitol compounds are useful inhibitors of glycosidases .