Sodium carbonate (Na2CO3, 1.590 g, 15 mmol) was added to a solution of glycine (12.5 mmol) in water (15 mL) under continuous stirring until completely dissolved. The solution was cooled to -5°C and p-toluenesulfonyl chloride (15 mmol) was added in four batches over 1 hour. The reaction mixture was continued to be stirred at room temperature for about 4 h. The progress of the reaction was monitored using thin layer chromatography (TLC, unfolding agent was MeOH/DCM, 1:9). Upon completion of the reaction, the mixture was acidified with 20% aqueous hydrochloric acid to pH 2. The crystals were collected by diafiltration and washed with pH 2.2 buffer. The pure product 2-(4-methylphenylsulfonamido)acetic acid was dried in a desiccator. The yield was 99.34% (2.8410 g) and the melting point was 88.4-88.6°C. FTIR (KBr, cm-1 ): 3448 (O-H, COOH), 3277 (N-H), 2957 (C-H, aliphatic), 1730 (C=O), 1598, 1440 (C=C), 1354, 1321 (2S=O). 1185 (SO2-NH), 1111, 1094 (C-N, C-O).1H NMR (DMSO-d6) δ: 7.90-7.88 (t, J=6.3 Hz, 1H, NH), 7.65-7.63 (d, J=8.6 Hz, 2H, ArH), 7.34-7.33 (d, J=8.05 Hz, 2H, ArH ), 3.52-3.51 (d, J=5.7 Hz, 2H, CH2), 2.34 (s, 3H, CH3).13C NMR (DMSO-d6) δ: 170.7 (C=O), 143.1, 138.4, 130.0, 127.1 (aryl carbons), 44.3 (CH2), 21.5 (CH3).HRMS-ESI (m/z): 228.0412 ([M-H]-, calculated value: 228.0408).
