5,6-Diamino-l,3-dimethyluracil hydrate (1.70 g, 10.0 mmol) and 4-formylcinnamic acid (1.76 g, 10.0 mmol) were refluxed in acetic acid (10 mL)-methanol (100 mL) for 0.5 hour. (E)-4[(6-Amino-l,2,3-4-tetrahydro-1,3-dimethyl-2,4-dioxo-5-pyrimidinyl)iminomethyl]cinnamic acid was precipitated as a yellow powder (1.84 g, 56%); mp 299°-301° C. with effervescence. Analysis for (C16H16N4O4): C,58.53;H,491;N,1707. Found: C,58.36;H,4.93;N,16.90. The structure was confirmed by H-NMR and EI mass spectrum. The (E)-4-[(6-amino-1,2,3,4-tetrahydro-1,3-dimethyl-2,4-dioxo-5-pyrimidinylmethyl]cinnamic acid (500 mg, 1.52 mmol) was then refluxed in nitrobenzene (125 mL) for 2.5 hours with slow distillation to remove water formed. The reaction mixture was cooled and the precipitate washed with ether. Recrystallization from N,N-dimethylformamide-water gave the monohydrate of the title compound as a pale yellow powder; mp>380° C. Analysis for (C16H14N4O4H2O):C, 55.81; H, 4.68; N, 16.27. Found: C, 56.05: H, 4.69; N, 16.27. The structure was confirmed by 1H-NMR and EI mass spectrum.
