Efficient Synthesis of Amine-Linked 2,4,6-Trisubstituted Pyrimidines as a New Class of Bacterial FtsZ Inhibitors.

We have recently identified a new class of filamenting temperature-sensitive mutant Z (FtsZ)-interacting compounds that possess a 2,4,6-trisubstituted pyrimidine-quinuclidine scaffold with moderate antibacterial activity. Employing this scaffold as a molecular template, a compound library of amine-linked 2,4,6-trisubstituted pyrimidines with 99 candidates was successfully established by employing an efficient convergent synthesis designed to explore their structure-activity relationship. The results of minimum inhibitory concentration (MIC) assay against strains and cytotoxicity assay against the mouse L929 cell line identified those compounds with potent antistaphylococcal properties (MIC ranges from 3 to 8 μg/mL) and some extent of cytotoxicity against normal cells (IC ranges from 6 to 27 μM). Importantly, three compounds also exhibited potent antibacterial activities against nine clinically isolated methicillin-resistant (MRSA) strains. One of the compounds, , exhibited low spontaneous frequency of resistance, low toxicity against larvae, and the ability to rescue larvae (20% survival rate at a dosage of 100 mg/kg) infected with a lethal dose of MRSA ATCC 43300 strain. Biological characterization of compound by saturation transfer difference NMR, light scattering assay, and guanosine triphosphatase hydrolysis assay with purified FtsZ protein verified that it interacted with the FtsZ protein. Such a property of FtsZ inhibitors was further confirmed by observing iconic filamentous cell phenotype and mislocalization of the Z-ring formation of . Taken together, these 2,4,6-trisubstituted pyrimidine derivatives represent a novel scaffold of FtsZ inhibitors.