Disclosed herein are antibacterial compounds that accumulate in Gram-negative bacteria, methods of preparing the compounds, and methods of using the compounds to inhibit or kill microbes, and methods of treating microbial infections, such as Gram-negative bacterial infections. Compounds selected for conversion to potential Gram-negative antibacterial compounds were identified based on compounds having low globularity and low flexibility. Amine substituents were then strategically added to the selected compounds to provide compounds having antibacterial activity against Gram-negative bacteria.