Sulfamethoxazole (SMX) is the most significant antibiotic in the sulfonamide family. It was chosen as the representative of this category because of its widespread use. Starting with sulfamethoxazole, a new series of 2-Azetidinone (M1-M6) was synthesized, the structure of these new derivatives was confirmed using spectral methods, starting with the synthesis of Schiff’s bases by reflux of different aromatic benzaldehydes, separately, with Sulfamethoxazole in ethanol with few drops of acetic acid. The final compounds were obtained by ketene-imine synthesis of β-lactam using chloroacetyl chloride. The designed chemicals’ synthesis has been completed successfully. Physical parameters (melting points and Rf values), Fourier transform infrared (FT-IR) spectroscopy, and Proton nuclear magnetic resonance (1H-NMR) spectroscopy were used to establish the purity and characterization of these derivatives. When compared to standard antibiotics (Sulfamethoxazole, Ciprofloxacin, and Fluconazole), the preliminary antimicrobial activity tests on four different bacteria strains and one type of fungus demonstrated that the final compounds (M1-M6) have significant activity. Finally, the new derivatives (M3 and M5) are the most potent than the other ones and more active than the standard drugs.