Synthesis of PSBC

Typically, AmP (1.1 g, 10.2 mmol) was first dissolved in DCM (15 mL) at room temperature. Under stirring, BOC (2.3 g, 10.5 mmol) solution in DCM (5 mL) was added and the obtained solution was stirred for another 7 h. Then, it was transferred into a funnel and washed with saline water three times (250 mL). The organic layer was collected and vacuum-concentrated at 50 °C to obtain 2 as yellow oil. The obtained 2 and PrS (1.6 g, 13.1 mmol) were refluxed overnight in chloroform (25 mL). The solvent was then removed to obtain the crudes of 3 as a brown solid. It was then dissolved in acidic D. I. water (20 mL) with the pH < 1. The resultant solution was stirred for 3 h at room temperature and then was concentrated under vacuum to remove the water, affording 4 as a yellow solid. Next, 4 and potassium carbonate (1.6 g, 11.6 mmol) were stirred in acetone (100 mL) for 30 min in an ice bath. The acetone solution (20 mL) of CyC (2.2 g, 11.9 mmol) was added and the resultant solution was stirred for another 8 h in the ice bath. After filtration, washing with acetone and dryness, PSBC was obtained as yellow powder. HRMS (ESI positive): m/z = 378.0191 ([M⁺ H]⁺), Calcd. for C₁₂H₁₄Cl₂N₅O₃S = 378.0189. ¹H NMR (D₂O/DMSO-d₆, ppm): 8.82 (d, 1H), 8.40 (t, J = 8.0, 1H), 7.93 (q, J = 8.0, 2H), 4.97 (s, 2H), 4.73 (t, J = 8.0, 2H), 2.85 (t, 2H), 2.32 (t, J = 8.0, 2H). ¹³C NMR (D₂O, ppm): 170.30, 169.64, 165.95, 160.27, 153.48, 146.19, 127.08, 56.16, 47.18, 41.54, 25.36.