Antimicrobial 1,3,4-trisubstituted-1,2,3-triazolium salts

A series of 1,3,4-trisubstituted-1,2,3-triazolium bromide salts were prepared by efficient two-step sequences of azide-alkyne cycloaddition and benzylic substitution. The antimicrobial activity of each triazolium salt and correlating triazole precursor was evaluated using a minimum inhibitory concentration (MIC) assay. MIC activities as low as 1 µM against Gram-positive bacteria, 8 µM against Gram-negative bacteria and 4 µM against fungi were observed for salt analogs, while neutral triazoles were inactive. Analogs representing selective and broad-spectrum antimicrobial activity were each identified. MIC structure-activity relationships observed within this motif indicate that the presence of cationic charge and balance of overall hydrophobicity are strongly impactful, while benzyl vs. aryl substituent identity and variation of substituent regiochemistry are not.