2-Difluoromethylpyridine as a bioisosteric replacement of pyridine-N-oxide: the case of quorum sensing inhibitorsElectronic supplementary information (ESI) available. See DOI: 10.1039/d1md00245g

Herein, we demonstrate that 2-difluoromethylpyridine is a bioisosteric replacement of pyridine-N-oxide. Using the quorum sensing inhibitor 4NPOas a model compound, a library of 2-difluoromethylpyridine derivatives was designed, synthesized, and evaluated toward quorum sensing activity, biofilm formation, anti-violacein activity, and protease activity. As a result, compounds 1(IC50of 35 ± 1.12 μM), 5(IC50of 19 ± 1.01 μM), and 6(IC50of 27 ± 0.67 μM) showed a similar or better activity in comparison to 4NPO(IC50of 33 ± 1.12 μM) in a quorum sensing system of Pseudomonas aeruginosa. In addition, compounds 1, 5, 6, and 4NPOshowed good antibiofilm biomass of Pseudomonas aeruginosaand reduced violacein production in Chromobacterium violaceum. In terms of protease activity, compounds 1, 5, and 6showed significant activity compared to 4NPO. Overall, the replacement of pyridine-N-oxide by 2-difluoromethylpyridine enhances the activity of the model compound, which could open a new path for bioisosteric replacement in drug discovery and development.