A new series of 2, 3-substituted quinazoline-4(3H)-ones were prepared by condensation of different amino acids with either 2-methyl or 2-phenyl- 4H-3,1-benzoxazin-4-one in refluxing pyridine. The structures of all compounds have been evaluated by elemental analysis and spectral analysis (IR, MS and 1H NMR). The antimicrobial activity of the newly synthesized compounds was tested and finally the structure activity relationship was described.