General procedure for the synthesis of 3-amino-3-(4-nitrophenyl)propionic acid from malonic acid and p-nitrobenzaldehyde: A mixture of 2.40 g of p-nitrobenzaldehyde, 2.44 g of malonic acid, and 3.54 g of ammonium acetate (molar ratio 1:1.1:2.3) was dissolved in 200 mL of 1 -butanol, and the reaction was carried out at reflux for 1.5-2 hr until the release of carbon dioxide gas stopped. Upon completion of the reaction, the precipitate formed was filtered and washed sequentially with boiling 1-butanol (2 x 50 mL), boiling ethanol (2 x 50 mL) and 100 mL of water. The precipitate was dried at 80-100°C for 8-10 hours. The purity of the product was checked by thin layer chromatography (TLC) and the reaction yield was about 65-80%.
