Antimicrob. outbreak of extensively-drug resistant (XDR)-Mtb threatens TB control and prevention efforts.4 Treatment duration for MDR-Mtb infections is at least 20-28 months. Tuberculosis chemotherapy for XDR-TB takes substantially longer than MDR-TB, and XDR-Mtb strains are responsible for very high mortality rate.5 Therefore, it is very important to discover new drugs that can shorten current TB drug regimens. Mechanisms that enter non-replicating (or dormant) state of Mtb are accounted for a significant factor that requires long-term chemotherapy.6 Wayne et. al. reported that oxygen starvation SIRPB1 is linked to TB drug resistance; upon depletion of oxygen in culture, Mtb terminates growth and develops into a characteristic dormant form.7,8 Significantly, the dormant form of Mtb was found to be resistant to most of clinically utilized antimycobacterial agents.8 Thus, new drugs targeting non-replicating Mtb are likely to revolutionize TB chemotherapy. The cell-wall of Mtb offers many unique targets for drug development.9 However, most of drugs associated with cell-wall biosynthesis have proven difficult to reduce treatment time of TB drug regimens due to the facts that this dormant bacteria are not actively synthesizing cell-walls.10 On the contrary, it was recently reported that a peptidoglycan biosynthesis inhibitor, meropenem (a (R)-Rivastigmine D6 tartrate carbapenem) was effective in killing non-replicating Mtb in combination with clavulanate (a -lactamase inhibitor).11 Although a mechanism of action of their bactericidal effect against dormant Mtb cells is not known, it is one of few examples that peptidoglycan biosynthesis inhibitors kill dormant form of Mtb. Because several translocase (R)-Rivastigmine D6 tartrate I (MurX/MraY, hereafter referred to as Mur X for translocase I) inhibitors kill Mtb much faster than other TB drugs under aerobic conditions (Physique 1),12 we commenced SAR studies of capuramycin (1), a known MurX inhibitor antibiotic, to improve efficacy of its antimycobacterial activity and (Physique 2).13,14,15 Daiichi-Sankyo and Sequella reported several capuramycin analogs in which MraY enzyme and antimycobacterial activity could be improved the modification of the carboxylic group of the capuramycin biosynthetic intermediate, A-500359.16,17,18,19 We have synthesized new capuramycin analogs our total synthetic scheme,15 in which all analogs are structurally different from the reported molecules and they are difficult to access from A-500359. In screening of new capuramycin analogs against replicating and non-replicating (dormant) Mtb, it was found that a 2-methylated capuramycin analog, UT-01320 (3) killed both replicating and non-replicating Mtb in microplate alamar blue assay (MABA) and Low-oxygen recovery assay (LORA), respectively.20 To the best of our knowledge, it is the first observation that a capuramycin analog exhibited bactericidal activity against non-replicating Mtb at low concentrations. Herein, we statement biological evaluations of 3, synergistic effect with known MurX inhibitors 1 or 2 2, and insights into a molecular target of 3 (Physique 2). Open in a separate window Physique 1 Biosynthesis of lipid II in and or RNA polymerase (RNAP) enzyme and 10 fluorescence dye. Tetrahydrofuran (THF), methylene chloride (CH2Cl2), dimethyformamide (DMF) were purified MBRAUN Solvent Purification Systems (MB-SPS) under an Argon atmosphere. Reactions were monitored by thin-layer chromatography (TLC) performed with 0.25 mm coated commercial silica gel plates (EMD, Silica Gel 60F254) using UV light for visualization at 254 nm, or developed with ceric ammonium molybdate or anisaldehyde or copper sulfate or ninhydrin solutions by heating on a hot plate. Reactions were also monitored by using SHIMADZU LCMS-2020 with solvents: A: 0.1% formic acid in water, B: acetonitrile. When necessary, reactions were monitored by SHIMADZU prominence HPLC using Phenomenex Kinetex 1.7 XB-C18 100A column (150 2.10 mm) and detected at 220, 254 nm. Flash chromatography was performed with Whatman silica gel (Purasil 60 ?, 230-400 Mesh). Proton magnetic resonance (1H-NMR) spectral data were recorded on 400, and 500 MHz devices. Carbon magnetic resonance (13C-NMR) spectral data were recorded on 100 and 125 MHz devices. For all those NMR spectra, chemical shifts ( H, C) were quoted in parts per million (ppm), and values were quoted in Hz. 1H and 13C NMR spectra were calibrated with residual undeuterated solvent (CDCl3: H =7.26 ppm, C =77.16ppm; CD3CN: H=1.94ppm, C =1.32ppm; CD3OD: H =3.31ppm, C =49.00 ppm; DMSO-d6: H=2.50ppm, C =39.5ppm; D2O: H=4.79 ppm) as an internal reference. The following abbreviations were used to designate the multiplicities: s=singlet, d=doublet, dd=double doublets, t=triplet, q=quartet, quin=quintet, hept=heptet, m=multiplet, br=broad. Bacterial strains The (R)-Rivastigmine D6 tartrate strains used were (ATCC 607) and H37Rv, H37Rv INHr, H37Rv RFPr, (ATCC 25019), (ATCC 6538D-5), (ATCC 349), (ATCC 8047), and (ATCC 27853). These bacteria were obtained from ATCC except for H37Rv (BEI Resources, NIAID). MIC assays Log phase bacterial culture A single colony of a bacterial strain (or and strains were produced on tryptic soy agar. The flasks were incubated overnight in (R)-Rivastigmine D6 tartrate a shaking incubator.