Salicylic acid heterocyclic derivatives: chemical synthesis and biological activity

Before a drug can be widely used, it must go through a long development process, starting from the discovery of the active ingredient and continuing with tests to confirm its safety and effectiveness. In this study, new olsalazine derivatives were synthesized, containing a fused morpholine-3-one ring and two five-membered heterocyclic rings (thiadiazole and oxadiazole). Common and readily available materials, such as salicylic acid (to prepare 2-hydroxy-5-nitrobenzoic acid) and inexpensive catalysts, were used to synthesize compounds from the first, 5,5'-(diazene-1,2-diyl)bis(2-hydroxy-3-nitrobenzoic acid) (A1), to the seventh, 6,6'-(diazene-1,2-diyl)bis(N-(4-(5-amino-1,3,4-oxadiazol-2-yl)phenyl)-3-oxo-3,4-dihydro-2H-benzo[b][1,4]oxazine-8-carboxamide) (A7). Each compound was characterized by FT-IR and ¹H-NMR spectroscopy, along with physical properties such as melting point and color. All compounds showed positive results, and their antibacterial activity was tested against Escherichia coli and Staphylococcus aureus, with several demonstrating effective inhibition.