21392-51-8

6628-81-5

109-77-3

21392-51-8

A mixture of acetic anhydride (16.9 g, 165 mmol), acetic acid (2.26 g, 37.6 mmol), triethylamine (19 g, 188 mmol), and 4-(dimethylamino)pyridine (0.1 g, 0.75 mmol) was added to a reaction flask and heated to 50 °C. Racemic alanine (6.79 g, 76.2 mmol) was added in small batches over a period of 4 h under stirring while maintaining the reaction temperature in the range of 45-55 °C. The reaction was carried out at a constant temperature in the range of 45-55 °C. The reaction temperature was kept at a constant temperature in the range of 45-55 °C. After the alanine addition was completed, the red mixture was continued to be stirred at 50 °C for 8 hours. Subsequently, acetic anhydride, acetic acid and triethylamine were removed by vacuum distillation (15-20 mbar) and the temperature of the system was gradually raised to a maximum of 100 °C. The residue of the resulting acylamino ketone intermediate (246) was cooled to room temperature and water (40 mL) was added. Next, malononitrile (4.71 g, 71.3 mmol) was added and the reaction mixture was slowly poured into 30% aqueous sodium hydroxide solution (25 mL), ensuring that the reaction temperature did not exceed 60 °C. The resulting mixture was cooled to 0 °C, filtered, washed with water (45 mL), and dried under vacuum to give 6.65 g of pyrrole derivative (7) in beige solid form in 66% yield; the melting point was 163-165 °C (literature value) [24].