Synthesis, characterization, and screening for analgesic and anti-inflammatory activities of new 1,3,4-oxadiazole derivatives linked to quinazolin-4-one ring

In the present study, several new 1,3,4-oxadiazole derivatives linked with quinazolin-4-one moiety were synthesized by following steps. 2-methyl -4H-3, 1-benzoxazin-4-one, and 2-phenyl -4H-3, 1-benzoxazin-4-one were synthesized in the first and second step by stirring anthranilic acid in pyridine with benzoyl chloride and with an acetic anhydride for 30 min at room temperature. On treatment with semicarbazide with the above synthesized intermediates, that is, 2-methyl-4H-3,1-benzoxazin-4-one, and 2-phenyl-4H-3,1-benzoxazin-4-one in the third step afforded 2-methyl-4-oxoquinazoline-3(4H)-carbohydrazide and 2-phenyl-4-oxoquinazoline-3(4H)-carbohydrazide. These were introduced in cyclization reaction with different aromatic acids, aromatic aldehydes, and carbon disulfide in the next step, producing the corresponding 3-(4-acetyl-5-aryl-4,5-dihydro-1,3,4-oxadiazol-2-yl)-2-phenyl-quinazolin-4(3H)-one derivatives, 3-(4-acetyl-5-aryl-4,5-dihydro-1,3,4-oxadiazol-2-yl)-2-methyl-quinazolin-4(3H)-one derivatives, 3-(5-aryl-1,3,4-oxadiazol-2-yl)-2-phenylquinazolin-4(3H)-one derivatives and 3-(5-aryl-1,3,4-oxadiazol-2-yl)-2-methylquinazolin-4(3H)-one derivatives. Purity of these synthesized derivatives was confirmed by thin layer chromatography, melting point. Structure of the derivatives was set up by determining infrared spectroscopy, nuclear magnetic resonance, and mass spectroscopy. All the synthesized derivatives were evaluated for their analgesic and anti-inflammatory activities in mice and rats. In animal studies, the derivatives 3-[4-acetyl-5-(2-hydroxyphenyl)-4,5-dihydro-1,3,4-oxadiazol-2-yl]-2-phenylquinazolin-4(3H)-one and 3-[4-acetyl-5-(4-hydroxy-3-methoxyphenyl)-4,5-dihydro-1,3,4-oxadiazol-2-yl]-2-phenylquinazolin-4(3H)-one shown more potent analgesic activity and the derivatives 3-[4-acetyl-5-(4-methoxyphenyl)-4,5-dihydro-1,3,4-oxadiazol-2-yl]-2-phenylquinazolin-4(3H)-one and 3-[4-acetyl-5-(4-methoxyphenyl)-4,5-dihydro-1,3,4-oxadiazol-2-yl]-2-methylquinazolin-4(3H)-one shown more potent anti-inflammatory activity as compared to other derivatives. The results of current study indicate that cyclization of carbohydrazide group of intermediate 2-methyl-4-oxoquinazoline-3(4H)-carbohydrazide and 2-phenyl-4-oxoquinazoline-3(4H)-carbohydrazide with different aromatic acids, aromatic aldehydes, and carbon disulfide produces novel quinazolin-4-one linked oxadiazole derivatives with potent analgesic and anti-inflammatory activities.