GENERAL METHOD: Glycine (1 mol), 22% sodium hydroxide solution and carbon disulfide (1 mol) were dissolved in 3 mL of water and placed in a microwave reactor (CEM Discover, Benchmate, USA) and reacted at 100°C for 5 min. After the reaction was completed, it was automatically cooled to 40 °C, sodium chloroacetate (1 mol) was added and the mixture was again reacted at 100 °C for 5 min. The reaction solution was cooled to 40 °C and concentrated. To the concentrate, 3 mL of hydrochloric acid was added and the reaction was continued at 110°C for 20-30 minutes. Upon completion of the reaction, the crude product was extracted with ethyl acetate and purified (refer to Nitsche and Klein, 2012 method). The product obtained was 2-(4-oxo-2-thioxothiazolidin-3-yl)acetic acid (2a) in 82.5% yield; melting point 245-247 °C; UV λmax 266, 215 nm; IR (KBr) νmax 3439, 1663, 1512, 1321, 896 cm-1; 1H NMR (DMSO-d6, 400 MHz): δ= 4.56 (2H, s, N-CH2), 4.41 (2H, s, H-5); 13C NMR (DMSO-d6, 100 MHz): δ= 202.80 (C=S, C-2), 173.72 (C=O, COOH), 167.29 (C=O, C-4), 44.77 (CH2, N-CH2), 35.94 ( CH2, C-5); elemental analysis (C5H5NO3S2) calculated values: C, 31.40; H, 2.64; N, 7.32. measured values: C, 31.55; H, 2.53; N, 7.22.
