Design and Synthesis of New Developed Sulfa Drugs via Introducing of Pyridine–Thiazole Moiety Followed by Screening of Their Antimicrobial Activity

Several novel antimicrobial agents with enhanced biological activity were designed and prepared by modifying three known sulfa drugs—sulfamethazine, sulfamerazine, and sulfamethoxazole—through the introduction of a pyridine–thiazole moiety. The synthesis involved four stages: (1) reaction of chloroacetyl chloride with 4-aminopyridine to obtain 4-(α-chloroacetamido)pyridine (1); (2) reaction of compound 1 with thiourea under microwave irradiation to form 2-amino-4-(pyridin-4-yl)thiazole (2); (3) chloroacetylation of sulfamethazine, sulfamerazine, and sulfamethoxazole to produce corresponding 4-(α-chloroacetamido) derivatives 3–5, and (4) reaction of thiazole derivative 2 with compounds 3–5 to obtain the desired novel pyridine–thiazole–sulfonamide hybrids 6–8. Antimicrobial screening against four bacterial strains and Candida albicans fungi demonstrated that the products exhibit significantly enhanced activity compared to the parent sulfonamide drugs. This confirms that introducing a pyridine–thiazole moiety is a successful strategy for increasing antimicrobial activity—a result validating our design hypothesis.