Anti-Helicobacter pylori agents. 5. 2-(Substituted guanidino)-4-arylthiazoles and aryloxazole analogues

Ferrocenyl palladacycles derived from unsymmetrical pincer-type ligands: evidence of Pd(0) nanoparticle generation during the Suzuki-Miyaura reaction and applications in the direct arylation of thiazoles and isoxazoles

A new family of ferrocenyl-palladacycle complexes Pd(L¹)Cl (Pd1) and Pd(L²)Cl (Pd2) were synthesized and characterized by UV-visible, IR, ESI-MS, and NMR spectral studies. The molecular structures of Pd1 and Pd2 were determined by X-ray crystallographic studies. Palladacycle catalyzed Suzuki-Miyaura cross-coupling reactions were investigated utilizing the derivatives of phenylboronic acids and substituted chlorobenzenes. Mechanistic investigation authenticated the generation of Pd(0) nanoparticles during the catalytic cycle and the nanoparticles were characterized by XPS, SEM and TEM analysis. Direct C-H arylation of thiazole and isoxazole derivatives employing these ferrocenyl-palladacycle complexes was examined. The reaction model for the arylation reaction implicating the in situ generation of Pd(0) nanoparticles was proposed.

Camphyl-based α-diimine palladium complexes: highly efficient precatalysts for direct arylation of thiazoles in open-air

Bulky camphyl-based α-diimine palladium complexes have been developed and exhibited high reactivity for the direct arylation of thiazoles in air.

Cu(i)-Catalyzed oxidative homo-coupling of thiazoline-4-carboxylates: synthesis of 4,4′-bithiazoline derivatives

Cu(i)-Catalyzed oxidative homo-coupling of thiazoline-4-carboxylates with good functional group tolerance has been developed.

Solid-phase synthesis of a library of amphipatic hydantoins. Discovery of new hits for TRPV1 blockade

Some heterocyclic systems, called privileged scaffolds, appear frequently in bioactive products and marketed drugs. The combination of a recognized privileged scaffold (hydantoin) and a functional group with high incidence in bioactive molecules (guanidine) guided the design of a library of amphipatic compounds, which allowed the discovery of novel TRPV1 ion channel blockers. The library was synthesized by parallel solid-phase synthesis from an orthogonally protected resin-bound Lys-Lys skeleton. Key steps of the synthetic procedure were the construction of the hydantoin ring, by reaction of the N-terminal amino group with N,N-disuccinimidyl carbonate (DSC) and subsequent base-induced cyclization, and the guanidinylation of the C-terminal Lys side-chain after removal of the Alloc protecting-group. The preliminary biological studies have allowed the identification of some of the key structural features directing the blockage of capsaicin-induced Ca(2+) influx through TRPV1 channels, particularly, the strong preference showed for highly lipophilic acyl groups and substituted guanidine moieties. Active compounds based on this new pharmacophoric scaffold that display in vitro and in vivo inhibitory activity.

Discovery, synthesis, and biological evaluation of a novel group of selective inhibitors of filoviral entry

Herein, we report the development of an antifiloviral screening system, based on a pseudotyping strategy, and its application in the discovery of a novel group of small molecules that selectively inhibit the Ebola and Marburg glycoprotein (GP)-mediated infection of human cells. Using Ebola Zaire GP-pseudotyped HIV particles bearing a luciferase reporter gene and 293T cells, a library of 237 small molecules was screened for inhibition of GP-mediated viral entry. From this assay, lead compound 8a was identified as a selective inhibitor of filoviral entry with an IC(50) of 30 μM. To analyze functional group requirements for efficacy, a structure-activity relationship analysis of this 3,5-disubstituted isoxazole was then conducted with 56 isoxazole and triazole derivatives prepared using "click" chemistry. This study revealed that while the isoxazole ring can be replaced by a triazole system, the 5-(diethylamino)acetamido substituent found in 8a is required for inhibition of viral-cell entry. Variation of the 3-aryl substituent provided a number of more potent antiviral agents with IC(50) values ranging to 2.5 μM. Lead compound 8a and three of its derivatives were also found to block the Marburg glycoprotein (GP)-mediated infection of human cells.