[Synthesis]
The general procedure for the synthesis of N-(4-fluorobenzoyl)-L-proline from 4-fluorobenzoyl chloride and L-proline was as follows: L-proline (2.5 g, 22 mmol) was dissolved in 5% NaOH solution (25 mL, 31 mmol), cooled to the appropriate temperature, and then 4-fluorobenzoyl chloride (3.17 g, 20 mmol) was slowly added dropwise under vigorous stirring. The reaction mixture was then supplemented with 5% NaOH solution (15 mL, 19 mmol) and stirred continuously for 1 hour at room temperature. After completion of the reaction, the mixture was cooled in an ice bath and the pH was adjusted to acidic by slowly adding 20% HCl solution (10 mL) until crystals were precipitated. The resulting crystals were filtered, washed with cold water and then dried in a desiccator using P2O5 as the drying agent. Finally, 4.21 g of N-(4-fluorobenzoyl)-L-proline crystals were obtained in 89% yield (based on a theoretical value of 88.8%). The product characterization data were as follows: molecular formula C12H12FNO3, molecular weight 237.23; melting point 174.0 °C; IR (NaCl, cm-1): 1735, 1605, 1585, 1514, 1440, 1230, 1180, 1161, 856, 762, 513; 1H NMR (CDCl3, δ, ppm). 7.64-7.61 (d, 2H, J=5.4 Hz), 7.59-7.57 (d, 2H, J=5.4 Hz), 7.16-7.07 (t, 2H, J=8.6 Hz). |