General procedure for the synthesis of 4-[[5-(aminosulfonyl)-1,3,4-thiadiazol-2-yl]amino]-4-oxobutanoic acid from succinic anhydride and 5-amino-1,3,4-thiadiazole-2-sulfonamide: To a solution of 5-amino-1,3,4-thiadiazole-2-sulfonamide (0.40 g, 2.22 mmol) in N,N-dimethylformamide was added Succinic anhydride (0.22 g, 2.22 mmol). The reaction mixture was heated at 100 °C with stirring for 12 hours. Upon completion of the reaction, the solvent was removed by rotary evaporator to afford the crude product 4-[[5-(aminosulfonyl)-1,3,4-thiadiazol-2-yl]amino]-4-oxobutanoic acid (0.60 g, 96% yield), which can be used in the next step of the reaction without further purification. The structure of the product was confirmed by the following characterization data: 1H NMR (400 MHz, DMSO-d6) δ 8.33 (s, 2H), 2.78 (t, J = 6.6 Hz, 2H), 2.62 (t, J = 6.4 Hz, 2H); 13C NMR (100 MHz, DMSO-d6) δ 174.08, 172.38, 164.52 , 162.15, 30.77, 29.08; HRMS (ESI+): m/z Calculated value C6H9N4O5S2 [M + H]+: 281.0014, measured value: 281.0009.