Tuberculosis (TB) remains one of the world's deadliest communicable diseases. Naturally derived antibiotics appear frequently in nature as collections of structurally similar compounds representing an adaptive evolutionary response to drug resistance development. Herein, we report an undescribed versicomycin (1), featuring an unprecedented post-nonribosomal peptide synthetase (NRPS) assembly line-modified skeleton, which was isolated from the marine-derived fungus. Gram-scale total synthesis of versicomycin (1) was accomplished using a hybrid synthesis strategy combining solid-phase chemistry, solution-phase cyclization, and chemical C–H bond functionalization. Inspired by this undescribed natural product (NP) skeleton, we efficiently developed a compound library comprising 89 natural product-like cycloheptapeptides (2–90) bearing aryl groups. Their antituberculosis activity, structure–activity relationships (SARs), and conformational effects along with in vitro and in vivo antibacterial effects were evaluated using Mycobacterium marinum. Remarkably, CHNQD-02353 (21), the most potent candidate, suppressed the proliferation of Mycobacterium tuberculosis H37Ra effectively with an MIC90 value of 0.25 μM, which is 300-fold lower than that of versicomycin (1). The in vitro study demonstrated that CHNQD-02353 exhibited biocompatibility and synergistic effects with major frontline drugs, indicating its broad clinical application potential. Further subcutaneous M. marinum infection study in mice revealed that CHNQD-02353 cleared bacteria effectively from lesions, demonstrating its in vivo anti-infective potential. These results show that our integrated research strategy has discovered a structurally untapped chemical class, representing a promising new area for antibiotic drug discovery.
Zhang et al. (Fri,) studied this question.