Synthesis, carbonic anhydrase inhibitory activity and antioxidant activity of some 1,3-oxazine derivatives

Hit, Lead & Candidate Discovery A series of 1-(6-methyl-2-substituted phenyl-4-thioxo-4H-1,3-oxazin-5-yl)ethanones (3a-n) were synthesized by the reaction of benzoyl isothiocyanates with active methylene compound acetylacetone in the presence of triethyl amine in a one-pot process. The structures of the products were elucidated by elemental analyses, FT-IR, ¹ H NMR, ¹³ C NMR, and mass spectroscopy. These new 1,3-oxazine derivatives were evaluated for their inhibitory activity against carbonic anhydrase II. Results for in vitro assay revealed that compound 3b having 4-methoxy phenyl moiety was the most potent inhibitor with IC₅₀ value of 0.144 ± 0.008 μM. It exhibited higher enzyme inhibitory activity as compared to the standard acetazolamide (IC₅₀  = 0.997 ± 0.061 μM). The compounds 3c, 3h, and 3n also displayed superior inhibitory activities compared to the rest of the synthesized oxazine derivatives. The radical scavenging activity of oxazine derivatives was also performed and it was found that compounds showed moderate antioxidant activity. Lipinski rule confirmed the therapeutic potential of the synthesized compounds. Molecular docking studies were also performed to further understand the binding affinity of these compounds with PDBID 1V9E which confirmed that the synthesized derivatives bind in the active binding site of the target protein. Based upon our results, it is proposed that compound 3b may serve as a lead structure to design more potent carbonic anhydrase inhibitors.