Nonhydrolyzable d­phenylalanine-benzoxazole derivatives retain antitubercular activity.

The emergence of drug resistant Mycobacterium tuberculosis, the causative agent of tuberculosis, demands the development of new drugs and new drug targets. We have recently reported that the d-phenylalanine benzoxazole Q112 has potent antibacterial activity against this pathogen with a distinct mechanism of action from other antimycobacterial agents. Q112 and previously reported derivatives were unstable in plasma and no free compound could be observed. Here we expand the structure-activity relationship for antimycobacterial activity and find nonhydrolyzable derivatives with decreased plasma binding. We also show that there is no correlation between antibacterial activity and inhibition of PanG, a putative target for these compounds.