The invention provides antimicrobial compounds and compositions, and methods of using them. The compounds and compositions include, for example, a compound of any one of Formulas I-X. The invention further provides methods of preparing the compounds, and useful intermediates for their preparation. The compounds can possess highly specific and selective activity, such as antibacterial activity and/or enzymatic inhibitory activity. Accordingly, the compounds and compositions can be used to treat bacterial infections, or to inhibit or kill bacteria, either in vitro or in vivo.