Design and Synthesis of Metabolically Stable tRNA Synthetase Inhibitors Derived from Cladosporin.

Selective and specific inhibitors of Plasmodium falciparum lysyl-tRNA synthetase represent promising therapeutic antimalarial avenues. Cladosporin was identified as a potent P. falciparum lysyl-tRNA synthetase inhibitor, with an activity against parasite lysyl-tRNA synthetase >100-fold more potent than that of the activity registered against the human enzyme. Despite its compelling activity, cladosporin exhibits poor oral bioavailability; a critical requirement for antimalarial drugs. Thus, the quest to develop metabolically stable cladosporin-derived analogues, while retaining similar selectivity and potency to that of the natural compound, has begun. Chemogenomic profiling of a designed library allowed an entirely innovative structure-activity relationship study to be initiated; this shed light on structural evidence of a privileged scaffold with a unique activity against tRNA synthetases.

Identification of Compounds that Selectively Stabilize Specific G-Quadruplex Structures by Using a Thioflavin†T-Displacement Assay as a Tool.

Small molecules are used in the G-quadruplex (G4) research field in vivo and in vitro, and there are increasing demands for ligands that selectively stabilize different G4 structures. Thioflavin T (ThT) emits an enhanced fluorescence signal when binding to G4 structures. Herein, we show that ThT can be competitively displaced by the binding of small molecules to G4 structures and develop a ThT-displacement high-throughput screening assay to find novel and selective G4-binding compounds. We screened approximately 28 000 compounds by using three different G4 structures and identified eight novel G4 binders. Analysis of the structural conformation and stability of the G4 structures in presence of these compounds demonstrated that the four compounds enhance the thermal stabilization of the structures without affecting their structural conformation. In addition, all four compounds also increased the G4-structure block of DNA synthesis by Taq DNA polymerase. Also, two of these compounds showed selectivity between certain Schizosaccharomyces pombe G4 structures, thus suggesting that these compounds or their analogues can be used as selective tools for G4 DNA studies.

Design and Synthesis of 2,2'-Diindolylmethanes to Selectively Target Certain G-Quadruplex DNA Structures.

G-quadruplex (G4) structures carry vital biological functions, and compounds that selectively target certain G4 structures have both therapeutic potential and value as research tools. Along this line, 2,2'-diindolylmethanes have been designed and synthesized in this work based on the condensation of 3,6- or 3,7-disubstituted indoles with aldehydes. The developed class of compounds efficiently stabilizes G4 structures without inducing conformational changes in such structures. Furthermore, the 2,2'-diindolylmethanes target certain G4 structures more efficiently than others and this G4 selectivity can be altered by chemical modifications of the compounds.

Gold(I) as an artificial cyclase: short stereodivergent syntheses of (-)-epiglobulol and (-)-4ß,7α- and (-)-4α,7α-aromadendranediols.

Three natural aromadendrane sesquiterpenes, (-)-epiglobulol, (-)-4ß,7α-aromadendranediol, and (-)-4α,7α-aromadendranediol, have been synthesized in only seven steps in 12, 15, and 17 % overall yields, respectively, from (E,E)-farnesol by a stereodivergent gold(I)-catalyzed cascade reaction which forms the tricyclic aromadendrane core in a single step. These are the shortest total syntheses of these natural compounds.

Rationale for the sluggish oxidative addition of aryl halides to Au(I).

The oxidative addition of Csp(2)-Br or Csp(2)-I bonds to gold(I) does not take place even under very favorable intramolecular conditions that could form five- or six-membered gold(III) metallacycles. DFT calculations reveal that although this process could be feasible thermodynamically, it is kinetically very sluggish.

Unlikeliness of Pd-free gold(I)-catalyzed Sonogashira coupling reactions.

The Sonogashira coupling reaction is not catalyzed by AuI/dppe in the absence of Pd complexes. However, addition of 0.1 mol % of Pd(0) led to efficient cross-coupling reactions. The most plausible catalytic cycles for the Au-catalyzed cross-coupling reactions have been examined and are unlikely in the absence of Pd contamination.