Green Synthesis of Novel Bis(1,2,3,4-tetrahydropyrimidines) and Impact of Rigid Linkers on Their In Vitro ACE Inhibitory and Antimicrobial Activities

This study focuses on the convergent one-pot, multicomponent greener synthesis of novel bis(1,2,3,4-tetrahydropyrimidines) via the renowned Biginelli reaction. Dialdehydes with five different rigid linkers were employed as key precursors for the target compounds. All reactions were performed under microwave irradiation and were complete within a few minutes. The target compounds were isolated with remarkable yields and high purity and characterized using up-to-date spectroscopic methods. All the synthesized compounds were tested for in vitro ACE inhibitory activity, as well as for antimicrobial activity against two Gram-positive and two Gram-negative bacterial strains and antifungal activity against Aspergillus flavus and Aspergillus niger. The results showed that the choice of linkers and the presence of sulfur or oxygen at the C2 position of the pyrimidine rings strongly affect the biological activity of the compounds. The highest ACE inhibitory activity with an IC50 value of 7.29 μg/mL was revealed in bis(1,2,3,4-tetrahydro-1,3-pyrimidine-2-thione) with an alkyne linker, and the same compound and its structural analog containing 1,3-pyrimidin-2-one moieties were identified as the most potent antibacterial agents.