Discovery and Development of the Covalent Hydrates ofTrifluoromethylated Pyrazoles as Riboflavin Synthase Inhibitors withAntibiotic Activity Against Mycobacterium tuberculosis

摘要

A high-throughput screening (HTS) hit compound displayed moderate inhibition of Mycobacteriumtuberculosis and Escherichia coli riboflavin synthases. The structure of the hit compound provided by thecommercial vendor was reassigned as [3-(4-chlorophenyl)-5-hydroxy-5-(trifluoromethyl)-4,5-dihydro-1H-pyrazol-1-yllio-tolyl)methanone (18). The hit compound had a k_(is)of 8.7 μM vs.M. tuberculosisriboflavin synthase and moderate antibiotic activity against both M. tuberculosis replicating phenotypeand nonreplicating persistent phenotype. Molecular modeling studies suggest that two inhibitormolecules bind in the active site of the enzyme, and that the binding is stabilized by stacking betweenthe benzene rings of two adjacent ligands. The most potent antibiotic in the series proved to be [5-(4-chlorophenyl)-5-hydroxy-3-(trifluoromethyl)-4,5-dihydro-1H-pyrazol-1-yl](m-tolyl)methanone (16),which displayed a minimum inhibitory concentration (MIC) of 36.6 μM vs. M. tuberculosis replicatingphenotype and 48.9 μM vs. M. tuberculosis nonreplicating phenotype. The HTS hit compound and itsanalogues provide the first examples of riboflavin synthase inhibitors with antibiotic activity.