Cyclic Amide-Linked Oxazolidinone Triazoles as Inhibitors of the T-Box Riboswitch.

Antimicrobial resistance remains a critical global health challenge, and was intensified by the COVID-19 pandemic. To address this growing threat, novel antibacterial agents targeting unconventional mechanisms are urgently needed. One promising strategy involves inhibiting bacterial riboswitches-RNA elements that regulate gene expression. Unlike most riboswitches that respond to small-molecule metabolites, the T-box riboswitch uniquely binds non-aminoacylated tRNA and is predominantly found in Gram-positive bacteria, making it an attractive target due to its conserved sequences and regulatory role over essential genes. This study explored oxazolidinone- and triazole-based compounds as potential inhibitors of the T-box riboswitch. Prior investigations into tricyclic oxazolidinones revealed an allosteric modulator that effectively inhibited T-box riboswitch transcriptional readthrough in vitro, though it showed limited disruption of the isolated tRNA-antiterminator complex. To enhance RNA-binding affinity and stereoselectivity, a macrocyclic oxazolidinone scaffold was designed, incorporating a strategic substituent to expand the interaction footprint. A synthetically viable candidate was identified, and computational docking studies suggested that one of the designed compounds may interfere with tRNA-induced transcription by forming π-π stacking interactions with G5 in the antiterminator region. These findings support the potential of targeting the T-box riboswitch with structurally optimized small molecules as a novel antibacterial strategy.