Synthesis, in Vitro Antimycobacterial and Antibacterial Evaluation of IMB-070593 Derivatives Containing a Substituted Benzyloxime Moiety

A series of novel IMB-070593 derivatives containing a substituted benzyloxime moiety and displaying a remarkable improvement in lipophilicity were synthesized and evaluated for their in vitro antimycobacterial and antibacterial activity. Our results reveal that the target compounds 19a–m have considerable Gram-positive activity (MIC: <0.008–32 µg/mL), although they are generally less active than the reference drugs against the Gram-negative strains. In particular, compounds 19h, 19j, 19k and 19m show good activity (MICs: <0.008–4 µg/mL) against all of the tested Gram-positive strains, including ciprofloxacin (CPFX)- and/or levofloxacin (LVFX)-resistant MSSA, MRSA and MSSE. Moreover, compound 19l (MIC: 0.125 µg/mL) is found to be 2–4 fold more active than the parent IMB070593, CPFX and LVFX against M. tuberculosis H37Rv ATCC 27294.