Recent developments in antimicrobial small molecule quaternary phosphonium compounds (QPCs) - synthesis and biological insights.

The development and characterization of quaternary phosphonium compounds (QPCs) have long benefitted from their incorporation into a cornerstone reaction in organic synthesis - the Wittig reaction. These structures have, more recently, been developed into a wide variety of novel applications, ranging from phase transfer catalysis to mitochondrial targeting. Importantly, their antimicrobial action has demonstrated great promise against a wide variety of bacteria. This review aims to provide an overview of recent development in non-polymeric biocidal QPC structures, highlighting their synthetic preparation, and comparing their antimicrobial performance. Discussions of similarities and dissimilarities to QACs are included, both in bioactivity as well as likely mechanism(s) of action. The observed potential of QPCs to eradicate Gram-negative pathogens via a novel mechanism is highlighted, as there is an urgent need to address the declining biocide arsenal in modern infection control.