Small molecule probes of the receptor binding site in the Vibrio cholerae CAI-1 quorum sensing circuit

Based on modification of separate structural features of the Vibrio cholerae quorum sensing signal, (S)-3-hydroxytridecan-4-one (CAI-1), three focused compound libraries have been synthesized and evaluated for biological activity. Modifications to the acyl tail and α-hydroxy ketone typically provided agonists with activities correlated to tail length and conservative changes to the hydroxy ketone. Among the molecules identified within this collection of agonists is Am-CAI-1 (B11), which is among the most potent agonists reported to date with an EC50 of 0.21 μM. Modifications to the ethyl side chain delivered molecules with both agonist and antagonist activity, including m-OH-Ph-CAI-1 (C13) which is the most potent antagonist reported to date with an IC50 of 36 μM. The molecules described in this manuscript are anticipated to serve as valuable tools in the study of quorum sensing in Vibrio cholerae and provide new leads in the development of an antivirulence therapy against this human pathogen.