Synthesis of 4-Nitrobenzenesulfonamide Derivative

Sodium carbonate (Na₂CO₃, 5 mmol) was added to a solution of 4-hydroxyproline (5 mmol) in water (15 mL) with continuous stirring until all the solutes dissolved. The solution was cooled to − 5 °C and 4-nitrobenzenesulfonyl chloride (5 mmol) was added in four portions over a period of 1 h. The reaction mixture was further stirred at room temperature for 4 h(Scheme 1). The mixture was acidified using 20% HCl until a pH of 2 was obtained. The white product obtained was filtered, washed, and dried in the open air. Yield (1.12 g, 71.34%), MP = 190–192 °(O), 1004 (C–N), 685 (S–N). ¹H-NMR (DMSO, 400 MHz) δ: 8.40 (m, 2H, ArH), 8.10 (m, 2H, ArH), 4.87 (s, 1H, OH exchangeable with HDO), 4.31 (m, 2H, CH-CO₂H and CH-OH), 3.59 (dd, 1H, CH_a of CH₂-CH-CO₂H, J = 8.00, 4.00 Hz) 3.41 (dt, 1H, CH_b of CH₂-CH-CO₂H, J = 8.00, 4.00 Hz), 2.19 (ddt, 1H, CH of CH2-N, J = 12.00, 8.00, 4.00 Hz), 2.06 (ddd, 1H, CH_b of CH₂-N, J = 12.00, 8.00,4.00 Hz).¹³C NMR (DMSO, 100 MHz) δ: 174.19 (C = O), 150.28, 143.40, 128.81, 123.79 (4 aromatic carbons), 69.21, 59.94, 56.51, 39.00 (4 aliphatic carbon). DEPT (100 MHz) δ: 174.19, 150.28, 143. 40 (tertiary C), 128.81, 123.79, 69.21, 59.94 (CH carbons), 56.51 and 39.00 (CH₂ carbons).