Novel 5-membered iminocyclitol derivatives were found to be a potent and selective inhibitors of the glycoprotein processing α- and β-glucosidase which were further found to be active antiviral agents against Japanese encephalitis virus, dengue virus serotype 2 (DEN-2), human SARS coronavirus and human β-hexosaminidase, a new target for development of osteoarthritis therapeutics.