Synthesis, Antiviral and Cytotoxic Activities of Some Novel 2, 3-Disubstituted Quinazolin-4(3H)-Ones

2-substituted benzoxazin-4-ones were condensed with trimethoprim and pyrimethamine to form the 2, 3-disubstituted quinazolin-4(3h)-ones. their chemical structure was elucidated by means of spectral (ft-ir, ih-nmr, ms) and elemental analysis. the antiviral activity and cytotoxicity of the compounds were tested in hela cells (vesicular stomatitis virus and respiratory syncytial virus), hel cells (herpes simplex- l and -2), vero cells(parainfluenza-3 , reovirus-l , sindbis virus, coxsackie virus b4 and punta toro virus) and mt-4 cells (hiv-l and 2) cell cultures. among the new derivatives evaluated, 3-[4-amino5(4-chlorophenyl)-6-ethylpyrimidin-2-yl ]-2-ethyl/phenyl-quinazolin-4(3h)-one (5b andsa) exhibited some activity with an mic of 9.6 ug/ml, against parainfluenza-3 virus, reo-lvirus and punta toro virus in vero cells. compounds 5a, sb and 5c also displayed markedcytostatic activity in lymphocyte (mt-4) cells. they were not active against hiv-l or -2 atnon-cytostatic concentrations.