Synthesis, antibacterial and anti-MRSA activity, in vivo toxicity and a structure-activity relationship study of a quinoline thiourea

We report the synthesis, antibacterial evaluation of a series of thiourea-containing compounds. 1-(3,5-Bis (trifluoromethyl) phenyl)-3-((S)-(6-methoxyquinolin-4-yl)-((1S, 2S, 4S, 5R)-5-vinylquinuclidin-2-yl) methyl) thiourea 5, was the most active against a range of Gram-positive and Gram-negative bacteria, and exhibited bacteriostatic activity against methicillin resistant Staphylococcus aureus (MRSA) comparable to that of the well-known antibacterial agent vancomycin. Quinoline thiourea 5 was subjected to a detailed structure-activity relationship study, with 5 and its derivatives evaluated for their bacteriostatic activity against both Gram-negative and Gram-positive bacteria. A number of structural features important for the overall activity of quinoline thiourea 5 have been identified. A selection of compounds, including 5, was also evaluated for their in vivo toxicity using the larvae of the Greater wax moth, Galleria mellonella. Compound 5, and a number of derivatives, were found to be non-toxic to the larvae of Galleria mellonella. A new class of antibiotic can result from the further development of this family of compounds. (C) 2015 Elsevier Ltd. All rights reserved.