N-Oxide heterocycles and imidazoles replacing ring D of calanolides against Mycobacterium tuberculosis

We have explored the chemistry of N-oxide heterocycles and imidazoles replacing ring D of the natural product (+)-calanolide A, and have synthesized 12 new analogues, two of which were active against both R Mtb and NR Mtb with MIC values of 12.5 μg/mL, which would lead to further optimization for more potent anti-TB candidates.