The general experimental procedure was as follows: glycine methyl ester hydrochloride (10 mmol) and sodium carbonate (2.1 g, 20 mmol) were dissolved in anhydrous dichloromethane (50 mL) and cooled in an ice bath. Subsequently, p-toluenesulfonyl chloride (1.9 g, 10 mmol) was added. The reaction mixture was stirred at room temperature overnight. After the reaction was completed, more dichloromethane was added and the organic layer was washed sequentially with 0.1 M hydrochloric acid, saturated sodium bicarbonate solution and brine. The organic phase was dried with anhydrous sodium sulfate and concentrated in vacuum to give the crude product. The crude product was purified by silica gel column chromatography using hexane and ethyl acetate (1:1) as eluent. Methyl 2-(4-methylphenylsulfonylamino)acetate (compound G2) was finally obtained in 78% yield as a white solid.1H NMR (400 MHz, CDCl3): δ 7.74 (d, J = 8.3 Hz, 2H, ArH), 7.31 (d, J = 8.3 Hz, 2H, ArH), 5.04 (t, J = 5.1 Hz, 1H, - NH-), 3.78 (d, J = 5.1 Hz, 2H, -CH2-), 3.64 (s, 3H, -OCH3), 2.42 (s, 3H, -CH3) ppm. 13C NMR (100 MHz, CDCl3): δ 169.4, 144.0, 136.3, 129.9, 127.4, 52.7, 44.2, 21.7 ppm. 21.7 ppm.Calculated elemental values [C10H13NO4S]: C, 49.37; H, 5.39; N, 5.76; S, 13.18.Measured values: C, 50.63; H, 5.09; N, 5.36; S, 12.87.
