An Efficient Synthetic Approach for the Synthesis of Pyrano[2,3-d]pyrimidinones and Their Antimicrobial, Antioxidant Studies

Objective: Synthesis of pyrano[2,3-d]pyrimidinone derivatives and evaluation of their antimicrobial and antioxidant activity. Methods: An efficient protocol for the synthesis of pyranopyrimidinone derivatives via a one-pot three-component condensation reaction of aryl aldehydes, malononitrile and barbituric acid in aqueous conditions using a phase transfer catalyst was employed. Physical and spectroscopic methods were used to assign the structures of the synthesized derivatives (IVa–IVj). The agar well diffusion method was used to test the in vitro antimicrobial activity of the compounds against Dickeya sp. (Gram-negative bacteria) and Streptomyces scabiei (Gram-positive bacteria). The antioxidant activity of the synthesized pyrimidinone derivatives (IVa–IVj) was evaluated by the H₂O₂ scavenging assay using ascorbic acid and gallic acid as the positive controls. Results and Discussion: A simple procedure, short reaction time, high yields (78–93%), broader substrate scope, easy handling of the catalyst and simple work-up, i.e., non-column chromatographic separation of the desired products were attractive features of this process. Synthesized compounds exhibited zone of inhibition at 10.67 ± 0.33, 9.50 ± 0.29, and 10.75 ± 0.14 mm in diameter for (IVf), (IVg), and (IVj), respectively against Dickeya sp., compared to Gentamicin as standard (zone of inhibition at 19.17 ± 0.22 mm). Using H₂O₂ scavenging assay, the derivatives (IVg), (IVj), (IVi), and (IVf) emerged to display promising antioxidant activities with inhibition percentages of 82.0 ± 0.3, 81.6 ± 0.3, 81.0 ± 0.2, and 77.0 ± 0.3 respectively, similar to the ascorbic acid and gallic acid (percent inhibition of 80.5 ± 0.3 and 79.5 ± 0.1, respectively) used as reference standards. Conclusions: The compounds (IVf–IVg), (IVi–IVj) possessing electron-donating groups were found to be potent towards antioxidant activity and could be potentially utilized to develop pharmaceutical products.