Resorcinol-based Bolaamphiphilic Quaternary Ammonium Compounds

Quaternary ammonium compounds (QACs) play crucial disinfectant roles in healthcare, industry, and domestic settings. Most commercially utilized QACs like benzalkonium chloride have a common architectural theme, leading to a rise in bacterial resistance and urgent need for novel structural classes. Some potent QACs such as chlorhexidine (CHX) and octenidine (OCT) feature a bolaamphiphilic architecture, comprised of two cationic centers at the molecular periphery and a non-polar region connecting them; these compounds show promise to elude bacterial resistance mechanisms. Inspired by such structures, we synthesized a series of 43 biscationic amphiphilic compounds focused on a resorcinol core, featuring flexibility of linker lengths, alkyl tails, and relative substituent positioning, to study their structure activity relationships (SARs). Antibacterial activity evaluation against a panel of gram-positive and gram-negative strains, including ESKAPE pathogens (A. baumannii, P. aeruginosa), were encouraging, with minimum inhibitory concentrations (MICs) of 0.5-4 μM against all tested strains for select compounds. Ten prepared compounds bearing either 17 or 18 total side chain carbons demonstrated uniformly strong antibacterial activity against P. aeruginosa (MIC 4-16 μM) and 6 other strains (MIC ≤4 μM), irrespective of cationic spacing. These findings promise to further extend the application of bolaamphiphilic QACs as a novel class of disinfectants.