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As part of our search for new antimicrobials and antibiotic enhancers, a series of naphthyl- and biphenyl-substituted polyamine conjugates have been synthesized. The structurally-diverse library of compounds incorporated variation in the capping end groups and in the length of the polyamine (PA) core. Longer chain (PA-3-12-3) variants containing both 1-naphthyl and 2-naphthyl capping groups exhibited more pronounced intrinsic antimicrobial properties against methicillin-resistant <i>Staphylococcus aureus</i> (MRSA) (MIC ≤ 0.29 µM) and the fungus <i>Cryptococcus neoformans</i> (MIC ≤ 0.29 µM). Closer mechanistic study of one of these analogues, <b>20f</b>, identified it as a bactericide. In contrast to previously reported diarylacyl-substituted polyamines, several examples in the current set were able to enhance the antibiotic action of doxycycline and/or erythromycin towards the Gram-negative bacteria <i>Pseudomonas aeruginosa</i> and <i>Escherichia coli</i>. Two analogues (<b>19a</b> and <b>20c</b>) were of note, exhibiting greater than 32-fold enhancement in activity. This latter result suggests that α,ω-disubstituted polyamines bearing 1-naphthyl- and 2-naphthyl-capping groups are worthy of further investigation and optimization as non-toxic antibiotic enhancers.