To p-toluenesulfonic acid 3-cyclopropyl-1-(2-fluoro-4-iodo-phenyl)-6,8-dimethyl-2,4,7-trioxo-1,2,3,4,7,8-hexahydro-pyrido[2,3-d]pyrimidin-5-yl ester 77 (28.0 g) and 3′-aminoacetanilide 57 (13.2 g) were added N,N-dimethylacetamide (84.0 ml) and 2,6-lutidine (15.3 ml), and the mixture was stirred at 130° C. for 4 hrs. After allowing to cool with stirring, methanol (196 ml) was added dropwise, and the mixture was stirred at room temperature. The crystals were collected by filtration and dried to give N-{3-[3-cyclopropyl-1-(2-fluoro-4-iodo-phenyl)-6,8-dimethyl-2,4,7-trioxo-1,2,3,4,7,8-hexahydro-pyrido[2,3-d]pyrimidin-5-ylamino]-phenyl}-acetamide 58 (25.2 g, yield 93%) as colorless crystals.
