Design and synthesis of novel arylurea derivatives of aryloxy(1-phenylpropyl) alicyclic diamines with antimicrobial activity against multidrug-resistant Gram-positive bacteria.

The alarming increase in the resistance of bacteria to the currently available antibiotics necessitates the development of new effective antimicrobial agents that are active against bacterial pathogens causing major public health problems. For this purpose, our in-house libraries were screened against a wide panel of clinically relevant Gram-positive and Gram-negative bacteria, based on which compound I was selected for further optimization. Synthetic efforts in a group of arylurea derivatives of aryloxy(1-phenylpropyl) alicyclic diamines, followed with an in vitro evaluation of the activity against multidrug-resistant strains identified compound 44 (1-(3-chlorophenyl)-3-(1-{3-phenyl-3-[3-(trifluoromethyl)phenoxy] propyl}piperidin-4-yl)urea). Compound 44 showed antibacterial activity against Gram-positive bacteria including fatal drug-resistant strains i.e., Staphylococcus aureus (methicillin-resistant, MRSA; vancomycin-intermediate, VISA) and Enterococcus faecium (vancomycin-resistant, VREfm) at low concentrations (0.78-3.125 µg/mL) comparable to last resort antibiotics (i.e., vancomycin and linezolid). It is also potent against biofilm-forming S. aureus and Staphylococcus epidermidis (including linezolid-resistant, LRSE) strains, but with no activity against Gram-negative bacteria (Escherichia coli, Klebsiella pneumoniae and Pseudomonas aeruginosa). Compound 44 showed strong bactericidal properties against susceptible and drug-resistant Gram-positive bacteria. Depolarization of the bacterial cytoplasmic membrane induced by compound 44 suggests a dissipation of the bacterial membrane potential as its mechanism of antibacterial action. The high antimicrobial activity of compound 44, along with its selectivity over mammalian cells (lung MCR-5 and skin BJ fibroblast cell lines) and no hemolytic properties toward horse erythrocytes, proposes arylurea derivatives of aryloxy(1-phenylpropyl) alicyclic diamines for development of novel antibacterial agents.