Synthesis, Characterization, and Antimicrobial Evaluation of Novel Thiohydrazonates and Pyrazolo[3,4-b]pyridines

Comprehensive analysis of crystal structure, spectroscopic properties, quantum chemical insights, and molecular docking studies of two pyrazolopyridine compounds: potential anticancer agents

In this study, two pyrazolo[3,4-b]pyridine derivatives (4a and 4b) were grown using a slow evaporation solution growth technique and characterized by FT-IR, HRMS, 1H/13C NMR spectroscopy, and X-ray crystallography. The 4a and 4b structures crystallized in monoclinic and triclinic systems with space groups P21/n and P1̄, respectively. Theoretical calculations were performed at the DFT/B3LYP level for the optimized geometries. The results were in excellent agreement with the experimental data (spectroscopic and XRD). This investigation encompasses molecular modeling studies including Hirshfeld surface analysis, energy framework calculations, and frontier molecular orbital analysis. Intermolecular interactions within the crystal structures of the compounds were explored through Hirshfeld surface analysis, which revealed the notable presence of hydrogen bonding and hydrophobic interactions. This insight provides valuable information on the structural stability and potential solubility characteristics of these compounds. The research was extended to docking analysis with eight distinct kinases (BRAF, HER2, CSF1R, MEK2, PDGFRA, JAK, AKT1, and AKT2). The results of this analysis demonstrate that both 4a and 4b interact effectively with the kinase-binding sites through a combination of hydrophobic interactions and hydrogen bonding. Compound 4a had the best affinity for proteins; this is related to the fact that the compound is not rigid and has a small size, allowing it to sit well at any binding site. This study contributes to the advancement of kinase inhibitor research and offers potential avenues for the development of new therapeutic agents for cancer treatment.

[3+2] Cycloaddition Synthesis of New Piperazine-Linked Bis(chromene) Hybrids Possessing Pyrazole Units as Potential Acetylcholinesterase Inhibitors

Two series of piperazine-linked bis(chromene) hybrids that are attached to pyrazole units were synthesized in the current study. Both series are attached to an acyl unit at pyrazole-C3, with one series attached to an acetyl unit and the other to an ethoxycarbonyl unit. A [3+2] cycloaddition protocol was conducted to produce the target hybrids with good yields by reacting the appropriate hydrazonoyl chlorides with chromene-based bis(enaminone) in dioxane containing triethylamine at reflux for 4 h. New hybrids were tested for acetylcholinesterase inhibitory activity at concentrations of 15 and 25 μM, as well as their ability to quench 2,2-diphenylpicrylhydrazyl (DPPH) free radicals at a concentration of 25 μg/mL. In general, the inhibitory activity is related to the electronic properties of the para-substituent that is attached to the arene unit at pyrazole-N1. Furthermore, the acyl unit attached to pyrazole-C3 has a significant effect on the new hybrids' inhibitory activity. At the previous concentrations, the (3-acetylpyrazole)-linked hybrid attached to p-NO₂ units demonstrated the best acetylcholinesterase inhibitory activity, with inhibition percentages of 79.7 and 90.2. Furthermore, the previous hybrid demonstrated the most effective DPPH inhibitory activity, with an inhibition percentage of 87.5.

1H-Pyrazolo[3,4-b]pyridines: Synthesis and Biomedical Applications

Pyrazolo[3,4-b]pyridines are a group of heterocyclic compounds presenting two possible tautomeric forms: the 1H- and 2H-isomers. More than 300,000 1H-pyrazolo[3,4-b]pyridines have been described which are included in more than 5500 references (2400 patents) up to date. This review will cover the analysis of the diversity of the substituents present at positions N1, C3, C4, C5, and C6, the synthetic methods used for their synthesis, starting from both a preformed pyrazole or pyridine, and the biomedical applications of such compounds.

3-Aminopyrazolo[3,4-b]pyridine: Effective Precursor for Barium Hydroxide-Mediated Three Components Synthesis of New Mono- and Bis(pyrimidines) with Potential Cytotoxic Activity

In this study, an efficient one-pot procedure for preparing a new series of pyrazolo[3,4-b]pyridine-fused pyrimidines was described. The target hybrids were developed through a three-component reaction of 3-amino-1H-pyrazolo[3,4-b]pyridine, benzaldehydes, and acetophenones (molar ratio 1 : 1 : 1). The best conditions for the previous reaction were 2.5 equivalents of barium hydroxide in DMF at 150 °C for 6 h. New bis(pyrimidines) were synthesized in high yields using a similar one-pot reaction protocol with some modifications. Thus, two equivalents of each of the appropriate acetophenones and 3-aminopyrazolopyridine were reacted with one equivalent of the appropriate bis(aldehydes). The reaction was carried out at 150 °C for 8 h using 4.5 equivalents of barium hydroxide in DMF. Repeating the previous reaction with the appropriate bis(acetyl) derivatives and benzaldehydes resulted in good yields of the target bis(pyrimidines). The in vitro cytotoxic activity of new pyrimidines against the MCF-7, HEPG2, and Caco2 cell lines was evaluated using the reference doxorubicin (IC₅₀ values of 4.34-6.97 μM). Hybrid 6h had the best activity against Caco2 and MCF-7 cell lines, IC₅₀ values of 12.62 and 14.50 μM, respectively. The IC₅₀ values for hybrids 6c, 6e, and 6f against MCF-7 and Caco2 cell lines were 23.99-41.69 and 33.14-43.33 μM, respectively. Furthermore, hybrid 6e displayed IC₅₀ value of 20.06 μM HEPG2 cell lines, while the hybrids 6c, 6f and 6h exhibited IC₅₀ values ranging between 26.29-50.51 μM. Furthermore, hybrid 6e had an IC₅₀ value of 20.06 μM for the HEPG2 cell lines, whereas hybrids 6c, 6f, and 6h had IC₅₀ values ranging from 26.29 to 50.51 μM.

Novel bis(pyrazole-benzofuran) hybrids possessing piperazine linker: Synthesis of potent bacterial biofilm and MurB inhibitors

Novel 1,4-bis[(2-(3-(dimethylamino)-1-oxoprop-2-en-1-yl)benzofuran-5-yl)methyl]piperazine was prepared and used as a key synthon for the this study. Therefore, 1,3-dipolar cycloaddition of this synthon with the appropriate hydrazonyl chlorides afforded a new series of bis(1,3,4-trisubstituted pyrazoles), linked via piperazine moiety. Furthermore, it reacted with hydrazine hydrate and phenyl hydrazine individually to afford the corresponding 1,4-bis[(2-(1H-pyrazolyl)benzofuran-5-yl)methyl]piperazines. Different bacterial strains and cell lines were selected to study the in-vitro antibacterial and cytotoxic activities for the new derivatives. 1,4-Bis[((2-(3-acetyl-1-(4-nitrophenyl)-1H-pyrazole-4-yl)carbonyl)benzofuran-5-yl)methyl]piperazine 5e showed the best antibacterial efficacies with MIC/MBC values of 1.2/1.2, 1.2/2.4 and 1.2/2.4 μM against each of E. coli, S. aureus and S. mutans strains, respectively. In addition, the inhibitory activity of some new bis(pyrazoles) as MRSA and VRE inhibitors were studied. Compound 5e gave the best inhibitory activity with MIC/MBC values of 18.1/36.2, 9.0/18.1 and 18.1/18.1 µM, respectively, against MRSA (ATCC:33591 and ATCC:43300) and VRE (ATCC:51575) bacterial strains, respectively. Compound 5e showed more effective biofilm inhibition activities than the reference Ciprofloxacin. It showed IC₅₀ values of 3.0 ± 0.05, 3.2 ± 0.08 and 3.3 ± 0.07 μM against S. aureus, S. mutans and E. coli strains, respectively. Furthermore, experimental study showed excellent inhibitory activities of 1,4-bis[((2-(3-substituted-1-aryl-1H-pyrazole-4-yl)carbonyl)benzofuran-5-yl)methyl]piperazine derivatives, attached to p-NO₂ or p-Cl groups, against MurB enzyme. Compound 5e gave the best MurB inhibitory activity with IC₅₀ value of 3.1 μM. The in-silico study was performed to predict the capability of new derivatives as potential inhibitors of MurB enzyme.