Imino sugars, such as deoxynojirimycin (DNJ), are glucose analogues that selectively inhibit cellular α-glucosidase I and II (enzymes that process N-linked glycans in glycoprotein) and exhibit broad spectrum antiviral activities against many enveloped viruses. Previously we have reported a novel DNJ derivative, OSL-95II, with antiviral activity and reduced cytotoxicity. In order to develop imino sugars with more potent antiviral activity as well as improved toxicity profile, OSL-95II was modified by diversifying the nitrogen linked alkylated side chain. The antiviral activities were initially tested in bovine viral diarrhea virus (BVDV) infected MDBK cells, yielding several imino sugar derivatives with novel structure and superior antiviral activity and toxicity profile. Furthermore, these new compounds were shown to be active against Dengue virus (DV) and West Nile virus (WNV) infection in BHK cells where potent anti-DV activity having submicromolar EC50 values and SI of greater than 900. These compounds represent a new generation of iminio sugars and their analogues, having application in the clinical treatment of infection of DV and other members of flaviviridae.