The increase in the incidence of antibiotic-resistant infections is a major concern to healthcare workers and requires the development of novel antibacterial agents. Recently, we described a series of benzophenone-containing antibiotics which displayed activity against antibiotic-resistant bacteria. We have shown that these agents function by disrupting the bacterial membrane. To further explore these compounds, a practical and efficient solution-phase parallel synthesis method was developed which allowed us to prepare combinatorial libraries of these agents. Using this method, we prepared 218 compounds in 58 reactions. All of the compounds were characterized by HPLC and MALDI-TOF mass spectrometry. Analysis of this library for antibacterial activity identified six compounds which displayed MIC values of 2.0 mg/L against Staphylococcus aureus. Examination of the structure-function relationships of these agents revealed that cationic groups were required and that cyclic, aliphatic amines were crucial for activity. Using the information generated here, we speculate on how the various structural features of the molecule are necessary for the interaction with the bacterial membrane.
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