In the search for polypharmacological quaternary ammonium compound disinfectants, we sought to investigate the quaternization of the ianthelliformisamine C scaffold. We synthesized a small library of quaternary ammonium compounds, finding that the tetramethyl derivative had the best activity. We investigated the mechanism of action of the natural product and methylated derivative, finding that both permeabilized the membrane.

Abstract

In the search for novel quaternary ammonium compound (QAC) disinfectants that can evade bacterial resistance, we turned to natural products as a source of inspiration. Herein we used natural product ianthelliformisamine C as a scaffold to design a small library of QACs. We first synthesized ianthelliformisamine C via an amide coupling that allowed for facile purification without the need for protecting groups. We then alkylated and quaternized the internal amines to yield four novel QACs, but all but one demonstrated no antibacterial activity against the tested strains. Using a combination of membrane depolarization and permeabilization assays, we were able to demonstrate that ianthelliformisamine C and the active QAC analog enact cell death via membrane permeabilization, contrary to prior reports on ianthelliformisamine C's mechanism of action.