Synthesis of Barbituric and Thiobarbituric Acids Bearing 5,6-Diphenyl-1,2,4-Triazin-3-yl Moiety as CDK2 Inhibitors of Tumor Cells

Synthesis of several new diphenyl-1',2',4'-triazin-3'-yl barbituric acid are described. The method involves addition reaction of isocyanate and isothiocyanate and 3-amino-5,6-diphenyl-1,2,4-triazine (1) to give N1,N3-disubstituted urea 2 and N1,N3-disubstituted thioureas 3 and 4 respectively. Further, ring closure reactions with malonate ester give barbituric acid 5 and thiobarbituric acid 6 and 7. The Presence of the active methylene in the skeleton of compound 5-7 at C-5 are deduced by condensation with pyridine-4-carboxyladehyde to give barbituric and thiobarbituric acids (8-10). Further fluoroacylation of compounds 5-7, afforded 1-(cyclohexyl/methyl/phenyl)-3-(5',6'-diphenyl-1',2',4'-triazin-3'-yl)-5-(trifluoracetyl)-5H-barbituric/thiobarbituric acids (11-13). Synthesis compounds of the series 5-(trifluoroacetyl) barbituric acid (11) and 5-(trifluoroacetyl) thiobarbituric acids (12 and 13) were able to inhibit activity of CDK2 in a biochemical assay with IC50 values comparable to olomoucine. In addition, a pyridine side chain at C-5 (compound 9 and 10) significantly decreases CDK2 inhibitory activity.