Step 3: To a methanolic (15 mL) suspension of the disulfone compound (0.62 g, 2.23 mmol) obtained in Step 2, a methanolic solution of 0.5 M sodium methanol (8.9 mL, 4.58 mmol) was slowly added. The reaction mixture was stirred at room temperature for 24 hours. After completion of the reaction, the homogeneous reaction solution was concentrated under reduced pressure to give a solid. The solid was suspended in ethanol (20 mL) and stirred at room temperature for 1 hour. Subsequently, the solid was separated by filtration and the filter cake was washed sequentially with ethanol (2 x 10 mL) and ether (2 x 10 mL). The resulting solid was dissolved in water (2 mL) and purified by passing through a C8 reversed-phase silica gel pad, using water as eluent. The eluate containing sodium 1,3-propanedisulfonate (P1, disodium salt) was collected and lyophilized to give sodium 1,3-propanedisulfonate (0.41 g, 85% yield) in white solid form. The structure of the product was confirmed by 1H NMR (D2O, 500 MHz): δ 1.84 (quintuple peak, J = 8.0 Hz, 2H), 2.44 (triple peak, J = 8.0 Hz, 4H).