Synthesis and biological studies of some 3-substituted-2,4(1H,3H)-quinazolinedione derivatives

In this thesis, twenty eight novel derivatives of 6,7-disubstituted-3-{2-[4-(substituted)piperazin-1-yl]-2-oxoethyl}quinazoline-2,4(1H,3H)-dione (compound 7-34) have been synthesized and their antimicrobial and anticancer activities were evaluated. Synthesis of the target compounds were started by the reaction of 4,5-disubstituted-2-aminobenzoic acid derivatives with ethyl isocyanatoacetate in basic media to form 4,5-disubstituted-2-[3-(2-ethoxy-2-oxoethyl)ureido]benzoic acid derivatives (compound 1-3). These products were submitted to the ring closure reaction by refluxing in concentrated hydrochloric acid to prepare 2-(6,7-disubstituted-2,4-dioxo-1,4-dihydroquinazolin-3(2H)-yl)acetic acid derivatives (compound 4-6). The target compounds, 6,7-disubstituted-3-{2-[4-substitutedpiperazin-1-yl]-2-oxoethyl} quinazoline-2,4(1H,3H)-dione derivatives (compound 7-34) were obtained by the amidation reaction of (6,7-disubstituted-2,4-dioxo-1,4-dihydroquinazolin-3(2H)-yl)acetic acid derivatives (compound 4-6) with various 1-substitutedpiperazines in the presence of DCC coupling reagent. Structure identifications of the compounds were done by 1H-NMR, UV and IR spectral methods and elemental analysis. 13C-NMR and mass spectral techniques were also applied for compounds 11, 20 and 32. Antimicrobial and anticancer activities of the compounds were examined by using disc diffusion and Sulforhodamine B test, respectively. Synthesized compounds were screened against two gram positive bacteria strains, Bacillus subtilis and Staphylococcus aureus, by using agar-based disc diffusion method. The compounds generally showed mild to moderate activity compared with ampicillin as standard. Among them, 3-[2-(4-Cyclohexylpiperazin-1-yl)-2-oxoethyl]-6,7-dimethoxyquinazoline-2,4(1H,3H)-dione (compound 29) exhibited the highest zone inhibition value of 14 mm against S. Aureus. According to the cytotoxicity screening results, the compounds generally showed moderate or no cytotoxic activity. 3-{2-[4-(4-Chlorobenzyl)piperazin-1-yl]-2-oxoethyl}quinazoline-2,4(1H,3H)-dione (compound 7) presented the highest activity against hepatoma (HUH-7), breast cancer (MCF-7) and colorectal cancer cell line (HCT-116) with the IC50 values of 2.5, 6.8 and 4.9 µM, respectively.