A Novel Approach to Synthesis of Quinazoline-4-One Derivatives and Studying Their Biological Applications

This study investigates the synthesis and biological activity of novel quinazoline-4-one derivatives, synthesized through Schiff base reactions involving hydrazine and various substituted benzaldehydes in ethanol. The synthetic route commenced with the reaction of phthalic anhydride with an amino acid, resulting in the formation of an aromatic amino acid. This intermediate underwent esterification with thionyl chloride and ethanol to yield an aromatic ester. The ester was subsequently converted to an aromatic hydrazide by reaction with 80% aqueous hydrazine in ethanol. The hydrazide was then reacted with different aromatic aldehydes in the presence of a small amount of glacial acetic acid to form the corresponding hydrazone derivatives. The final step, involved synthesizing quinazoline-4-one derivatives by reacting the hydrazone with anthranilic acid. The structures of the synthesized compounds were characterized by using various spectroscopic techniques, including FT-IR, ¹H-NMR, and ¹³C-NMR. The synthesized compounds showed dose-dependent inhibitory activity against Staphylococcus aureus and Escherichia coli, with higher concentrations (75 mg/mL) yielding greater inhibition. Compound A4 was the most effective, but its activity was lower compared to standard antibiotics like amoxicillin and ciprofloxacin. These findings indicate significant antimicrobial potential.