The 1,2,5-Thiadiazolidin-3-one 1,1-dioxide scaffold was used in the design and synthesis of inhibitors of Dengue Virus and West Nile Virus proteases and human tryptase. The scaffold was successfully used in the synthesis of potential inhibitors of Dengue Virus and West Nile Virus proteases. Inhibitors of Human tryptase synthesized based on the 1,2,5-Thiadiazolidin-3-one 1,1- dioxide scaffold were shown to be effective mechanism-based inhibitors of the enzyme.