Significance The global problem of TB has worsened in recent years with the emergence of drug-resistant organisms, and new drugs are clearly needed. In a cell-based high-throughput screen, a small molecule, TCA1, was discovered that has activity against replicating and nonreplicating Mycobacterium tuberculosis . It is also efficacious in acute and chronic rodent models of TB alone or combined with frontline TB drugs. TCA1 functions by a unique mechanism, inhibiting enzymes involved in cell wall and molybdenum cofactor biosynthesis. This discovery represents a significant advance in the search for new agents to treat persistent and drug-resistant TB.

Orlistat, or tetrahydrolipstatin (THL), is an FDA-approved antiobesity drug with potential antitumor activities. Cellular off-targets and potential side effects of Orlistat in cancer therapies, however, have not been extensively explored thus far. In this study, we report the total of synthesis of THL-like protein-reactive probes, in which extremely conservative modifications (i.e., an alkyne handle) were introduced in the parental THL structure to maintain the native biological properties of Orlistat, while providing the necessary functionality for target identification via the bio-orthogonal click chemistry. With these natural productlike, cell-permeable probes, we were able to demonstrate, for the first time, this chemical proteomic approach is suitable for the identification of previously unknown cellular targets of Orlistat. In addition to the expected fatty acid synthase (FAS), we identified a total of eight new targets, some of which were further validated by experiments including Western blotting, recombinant protein expression, and site-directed mutagenesis. Our findings have important implications in the consideration of Orlistat as a potential anticancer drug at its early stages of development for cancer therapy. Our strategy should be broadly useful for off-target identification against quite a number of existing drugs and/or candidates, which are also covalent modifiers of their biological targets.

Catalytic asymmetric hydrogenations of prochiral unsaturated compounds, such as olefin, ketone, and imine, have been intensively studied and are considered as a versatile method of creating a chiral carbon center. 1 However, asymmetric hydrogenation of heteroaromatic compounds is less explored, resonance stability of heteroaromatic compounds might impede the enantioselective hydrogenation. 2 To date, only a few papers on homogeneous asymmetric hydrogenation of heteroaromatic compounds have been reported. Kuwano and co-workers reported a highly effective hydrogenation of N-Boc-or Ac-substituted indoles by application of Rh/Ph-TRAP/Cs 2 CO 3 catalyst, 3 and up to 95% ee was obtained. Bianchini developed an orthometalated dihydride iridium complex for hydrogenation of 2-methylquinoxaline with 90% ee. 4 Studer and co-workers employed Rh(NBD) 2 BF 4 /DIOP as the catalyst for hydrogenation of monosubstituted pyridine and furans with only 24-27% ee. 5a Rh(DIOP)H was used as the catalyst for hydrogenation of 2-methylquinoxaline with only 3% ee. 5b The search for a new catalytic system for asymmetric hydrogenation of heteroaromatic compounds is still a challenge.Direct hydrogenation of easily available quinoline derivatives is the most convenient route to synthesize tetrahydroquinoline derivatives, which are important organic synthetic intermediates 6 and structural units of alkaloids and biologically active compounds. 7 Although many efforts have been made toward development of hydrogenation of quinolines using homogeneous achiral Rh 8 or Ru 9 catalysis, to the best of our knowledge, no report on homogeneous asymmetric hydrogenation of quinolines has appeared in the literature. Therefore, we decided to focus on this reaction. In this communication, we report our preliminary results and describe the first example of highly enantioselective iridium-catalyzed hydrogenation of quinolines.Considering that iridium has been successfully applied to asymmetric hydrogenation of imines and unfunctionalized olefins recently, 1 we first examined the [Ir(COD)Cl] 2 /MeO-Biphep/DCM system for hydrogenation of 2-methylquinoline (1a) (Scheme 1). Unfortunately, it was found that the catalytic activity is very low, and only a trace amount of product with low ee was obtained when the reaction was carried out in methylene chloride at room temperature under 700 psi of hydrogen for 18 h. A number of literature reports have appeared documenting the dramatic impact of additives on catalytic turnover and enantioselectivity. 10 Accordingly, we evaluated a number of additives, such as I 2 11 n-Bu 4 NI, 12,13 BiI 3 , 13 phthalimide, 14 benzylamine, 15 etc., in an attempt to promote reaction turnover. Gratifyingly, iodine proved to be the most efficient additive in this reaction. Chiral iridium complex prepared in situ from [Ir(COD)Cl] 2 and chiral bisphosphine (R)-MeO-Biphep were employed as catalysts, and the reactions were carried out at room temperature under 700 psi of hydrogen with a substrate: [Ir]: ligand:I 2 ratio of 100:0.5:1.1:10. Furt...

Tyrosine phosphorylation is a common protein posttranslational modification, which plays a critical role in signal transduction and the regulation of many cellular processes. Using a pro-peptide strategy to increase cellular uptake of O-phosphotyrosine (pTyr) and its nonhydrolyzable analog 4-phosphomethyl-L-phenylalanine (Pmp), we identified an orthogonal aminoacyl-tRNA synthetase/tRNA pair that allows the site-specific incorporation of both pTyr and Pmp into recombinant proteins in response to the amber stop codon in Escherichia coli in good yields. The X-ray crystal structure of the synthetase reveals a reconfigured substrate binding site formed by non-conservative mutations and substantial local structural perturbations. We demonstrate the utility of this method by introducing Pmp into a putative phosphorylation site whose corresponding kinase is unknown and determined the affinities of the individual variants for the substrate 3BP2. In summary, this work provides a useful recombinant tool to dissect the biological functions of tyrosine phosphorylation at specific sites in the proteome.