Synthesis and in vitro antimycobacterial and isocitrate lyase inhibition properties of novel 2-methoxy-2′-hydroxybenzanilides, their thioxo analogues and benzoxazoles

A new series of 2-methoxy-2′-hydroxybenzanilide derivatives and their thioxo analogues have been synthesised and characterised by IR, NMR and elemental analysis. These compounds were investigated for their in vitro antimycobacterial activities against Mycobacterium tuberculosis 331/88, Mycobacterium avium 330/88, Mycobacterium kansasii 235/80, clinically isolated M. kansasii 6509/96 and the ability to act as in vitro isocitrate lyase inhibitors. The best ICL inhibitors were two compounds from the thiobenzanilide group (8f, 8m), which exhibited an inhibition potential that was equal to the standard compound, 3-nitropropionic acid. In addition, the best antimycobacterial properties were exhibited by benzanilide derivatives 6h, 6k and 6l with 5-Cl and 4′ or 5′ Cl/Br substitution. For all the thiobenzanilide derivatives tested, two conformers were observed in the NMR spectra, which is most likely due to the hindered rotation of the C–N bond.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► New series of 2-methoxy-2′-hydroxybenzanilides and their thioxo analogues were prepared. ► Thiobenzanilides exhibited E, Z conformation due to the rigidity of the CS–NH bond. ► Two thiobenzanilides had equal isocitrate lyase inhibition as the standard. ► Antimycobacterial evaluation showed medium activity.