Synthesis, in-vitro biological evaluation, and molecular docking study of novel spiro-β-lactam-isatin hybrids

In our ongoing search for bioactive compounds, a class of novel spiro-β-lactam isatin hybrids has been synthesized through a [2 + 2] cycloaddition reaction from 1-allyl-3-(arylimino)indolin-2-one, ketenes and various aryloxy acetic acids. The formation of all cycloadducts was confirmed by FTIR, 1H NMR, 13C NMR, and mass spectroscopy as well as elemental analyses. The new β-lactams were subsequently evaluated for their biological activities demonstrating moderate to good activities against P. falciparum K1 strain. Among them, 4b and 4e lead to the best results with IC50 of 5.04 and 7.18 µM, respectively. The molecular docking simulation of 4b with P. falciparum dihydrofolate reductase enzyme (PfDHFR) binding site presented several important intermolecular interactions. All the synthesized β-lactams were also evaluated for their antimicrobial activities against both Gram-positive (S. aureus ATCC 25923) and Gram-negative bacteria (E. coli ATCC 28922, P. aeruginosa ATCC 27853) but unfortunately MICs up to 200 µg/mL were encountered in all cases.