A solution of 13.0 g (75 mmol) of N-acetyl-DL-leucine, 10.5 ml (75 mmol) of triethylamine, and 150 ml of dichloromethane is stirred at -10° and 9.75 ml (75 mmol) of isobutyl chloroformate is added. The reaction mixture is stirred for 1/2 hour at -10° C. and a cold solution of 11.6 g (50 mmol) of 2-[4-aminophenyl)-4-hydroxy-5-pyrimidine carboxylic acid and 7.7 (55 mmol) of triethylamine in 200 ml of dimethylformamide is added. The mixture is stirred at 5° C. for 3 hrs and overnight at room temperature. The reaction mixture is evaporated and the residue treated with water. The pH is lowered to 2.5 with dilute hydrochloric acid and the solid filtered, washed with water, and dried to give 13.8 g of 2-[4-(N-acetyl-DL-leucylamino)phenyl]-4-hydroxy-5-pyrimidine carboxylic acid; mp 233°-235° C. dec.
