Screening of quinoline, 1,3-benzoxazine, and 1,3-oxazine-based small molecules against isolated methionyl-tRNA synthetase and A549 and HCT116 cancer cells including an in silico binding mode analysis.

Elevated activity of methionyl-tRNA synthetase (MRS) in many cancers renders it a possible drug target in this disease area, as well as in a series of parasitic diseases. In the present work, we report the synthesis and in vitro screening of a library of 1,3-oxazines, benzoxazines and quinoline scaffolds against human MRS. Among the compounds tested, 2-(2-butyl-4-chloro-1-(4-phenoxybenzyl)-1H-imidazol-5-yl)-5-(4-methoxyphenyl)-1-oxa-3-azaspiro[5.5]undecane (compound 21) and 2-(2-butyl-4-chloro-1-(4-nitrobenzyl)-1H-imidazol-5-yl)-2,4-dihydro-1H-benzo[d][1,3]oxazine (compound 8) were found to be potent inhibitors of MRS. Additionally, these compounds significantly suppressed the proliferation of A549 and HCT116 cells with IC50 values of 28.4, 17.7, 41.9, and 19.8 µM respectively. Molecular docking studies suggested that the ligand binding orientation overlaps with the original positions of both methionine and adenosine of MRS. This suggests the binding of compound 21 against MRS, which might lead the inhibitory activity towards cancer cells.