MnO2-Mediated Oxidative Cyclization of "Formal" Schiff's Bases: Easy Access to Diverse Naphthofuro-Annulated Triazines

A different type of MnO₂-induced oxidative cyclization of dihydrotriazines has been developed. These dihydrotriazines are considered as a "formal" Schiff's base. This method provided easy access to naphthofuro-fused triazine via the C-C/C-O oxidative coupling reaction. The reaction sequence comprised the nucleophilic addition of 2-naphthol or phenol to 1,2,4-triazine, followed by oxidative cyclization. The scope and limitations of this novel coupling reaction have been investigated. Further application of the synthesized compound has been demonstrated by synthesizing carbazole-substituted benzofuro-fused triazines. The scalability of the reaction was demonstrated at a 40 mmol load. The mechanistic study strongly suggests that this reaction proceeds through the formation of an O-coordinated manganese complex.

Application of the Meerwein reaction of 1,4-benzoquinone to a metal-free synthesis of benzofuropyridine analogues

Several new heterocyclic systems based on a hydroxybenzofuro[2,3-b]pyridine building block were prepared. This benzofuropyridine is easily available from the Meerwein reaction of benzoquinone and a heterocyclic diazonium salt, followed by reduction and cyclization. Electrophilic substitution and further condensations give polycyclic systems, including oxazolo- and chromeno-fused analogues.

Inhibition of cyclin-dependent kinase CDK1 by oxindolimine ligands and corresponding copper and zinc complexes

Oxindolimine-copper(II) and zinc(II) complexes that previously have shown to induce apoptosis, with DNA and mitochondria as main targets, exhibit here significant inhibition of kinase CDK1/cyclin B protein. Copper species are more active than the corresponding zinc, and the free ligand shows to be less active, indicating a major influence of coordination in the process, and a further modulation by the coordinated ligand. Molecular docking and classical molecular dynamics provide a better understanding of the effectiveness and kinase inhibition mechanism by these compounds, showing that the metal complex provides a stronger interaction than the free ligand with the ATP-binding site. The metal ion introduces charge in the oxindole species, giving it a more rigid conformation that then becomes more effective in its interactions with the protein active site. Analogous experiments resulted in no significant effect regarding phosphatase inhibition. These results can explain the cytotoxicity of these metal complexes towards different tumor cells, in addition to its capability of binding to DNA, and decreasing membrane potential of mitochondria.

Molecular dynamics simulations of amyloid fibrils: an in silico approach

Amyloid fibrils play causal roles in the pathogenesis of amyloid-related degenerative diseases such as Alzheimer's disease, type II diabetes mellitus, and the prion-related transmissible spongiform encephalopathies. The mechanism of fibril formation and protein aggregation is still hotly debated and remains an important open question in order to develop therapeutic method of these diseases. However, traditional molecular biological and crystallographic experiments could hardly observe atomic details and aggregation process. Molecular dynamics (MD) simulations could provide explanations for experimental results and detailed pathway of protein aggregation. In this review, we focus on the applications of MD simulations on several amyloidogenic protein systems. Furthermore, MD simulations could help us to understand the mechanism of amyloid aggregation and how to design the inhibitors.