Synthesis and Evaluation of Substituted Pyrazoles: Potential Antimalarials Targeting the Enoyl‐ACP Reductase of Plasmodium Falciparum

A series of 1,5‐ and 1,3‐diarylsubstituted pyrazoles were designed, synthesized, and evaluated for their ability to inhibit enoyl‐ACP reductase of Plasmodium falciparum. The inhibitory activity of these synthesized compounds was evaluated in a continuous spectrophotometric assay. Of all the compounds analyzed, NAS‐81 and NAS‐39 inhibited the enzyme with IC₅₀ values of 30 µM and 50 µM, respectively. The mode of ligand binding was investigated by docking the synthetic inhibitors at the active site of the crystal structure of the enzyme.     

Microwave‐Assisted Rapid and Straightforward Synthesis of Novel 6‐(Aroxymethyl)‐2‐aryl‐6,7‐dihydropyrazolo[5,1‐c][1,4]oxazin‐4‐one Derivatives

A series of novel 6‐(aroxymethyl)‐2‐aryl‐6,7‐dihydropyrazolo[5,1‐c][1,4] oxazin‐4‐one derivatives was synthesized from ethyl 3‐aryl‐1H‐pyrazole‐5‐carboxylate and 2‐aryloxymethylepoxide by a microwave‐assisted, one‐step method in good yields. The microwave‐assisted reaction of ethyl 3‐aryl‐1H‐pyrazole‐5‐carboxylate and 2‐aryloxymethylepoxide proceeds with higher regioselectivity and is more economical and environmentally friendly in contrast to the normal intramolecular esterification route. A tandem mechanism of the reaction was proposed.     

Synthesis of Some Pyrazolo[3, 4]pyrimidine Derivatives for Biological Evaluation

Abstract

A novel β -enaminonitrile of 1-(6-p-tolyl-pyridazin-3-yl)-pyrazole derivative 2 was formed using (6-p-tolyl-pyridazin-3-yl)-hydrazine ( 1 ) and 2-ethoxymethylenemalononitrile. The β-enaminonitrile derivative 2 was in turn used as a precursor for the preparation of pyrazoles ( 4 , 6 ), pyrazolo[3, 4-d]-pyrimidines ( 3 , 7–12 ) and pyrazolo[4, 3-e][1,2,4]triazolo[4,3-c]pyrimidine ( 13 ). Also, N- and S-acyclic nucleosides 14 and 15 were prepared. Some of the prepared products showed potent antimicrobial activity.     

Ketene dithioacetal mediated synthesis of 1,3,4,5-tetrasubstituted pyrazole derivatives and their biological evaluation

Abstract

Ketene dithioacetal mediated chemo- and regioselective synthesis of a series of novel 1,3,4,5-tetrasubstituted pyrazole derivatives (4a-l) integrated with a bioactive indole nucleus was achieved by reacting substituted 2-(1-methyl-1H-indole-3-carbonyl)-3,3-bis-(methylthio)-acrylonitrile (2) and substituted phenyl hydrazine hydrochloride (3) in the presence of a catalytic amount of anhydrous K₂CO₃ under reflux conditions. The structures were ascertained by ¹H NMR, NOESY, ¹³C NMR, FT-IR, and HRMS data. In vitro cytotoxicity evaluation of the synthesized compounds against MCF 7 (breast carcinoma) and normal Vero (monkey kidney) cell lines revealed that the compound 5-(5-Bromo-1-methyl-1H-indol-3-yl)-1-(4-cyano-phenyl)-3-methylsulfanyl-1H-pyrazole-4-carbonitrile (4k) showed significant cytotoxicity against MCF 7 (GI₅₀ = 15.6 µM) with low cytotoxicity against normal Vero cell line. Most of the synthesized compounds were also found to possess excellent anti-inflammatory and antioxidant (DPPH, NO, H₂O₂ and SOR) potential.     

Synthesis,Dimeric Crystal Structure,and Fungicidal Activity of 1-(4-Methylphenyl)-2-(5-((3,5-dimethyl-1H-pyrazol-1-yl)methyl)-4-phenyl-4H-1,2,4-triazol-3-ylthio)ethanone

Abstract

A new triazole compound, C₄₆H₄₆N₁₀O₂S₂, has been synthesized, and the crystal structure was determined by a single crystal X-ray diffraction study. The fungicidal activity of the title compound was determined, and the results showed that it displays moderate fungicidal activity.

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GRAPHICAL ABSTRACT      

Insight into the Structural Requirements of Protoporphyrino- gen Oxidase Inhibitors： Molecular Docking and CoMFA of Di- phenyl Ether, Isoxazole Phenyl, and Pyrazole Phenyl Ether

Protoporphyrinogen oxidase （PPO, EC 1.3.3.4） is one of the most significant targets for a large family of in- hibitors that may be used as herbicide, bactericide, fungicide, or photosensitizing activator to treat cancer through photodynamic therapy （PDT）. Molecular docking and CoMFA were combined in a multistep framework with the ultimate goal of identifying important factor contributing to the activity of PPO inhibitors. As a continuation of the previous research work on the development of new PPO inhibitors, the bioassay results indicated that good PPO in- hibitors were discovered in all of the three chemical series with ICs0 values ranging from 0.010 to 0.061 pmol·L ^-1. Using the crystal structure of tobacco mitochondrial PPO （mtPPO） as template, all the compounds were docked into the enzyme active site. The docking pose of each compound was subsequently used in a receptor-based alignment, leading to the development of a significant CoMFA model with r^2 value of 0.98 and q^2 （cross validation r^2） value of 0.63. This novel multistep framework gives insight into the and it can be extended to other classes of PPO inhibitors. In be particularly applicable in virtual screening procedures. structural characteristics for the binding of inhibitors, addition, the simplicity of the proposed approach may     

Cobalt Complexes with Pyrazole Ligands as Catalyst Precursors for the Peroxidative Oxidation of Cyclohexane: X‐ray Absorption Spectroscopy Studies and Biological Applications

[CoCl(μ‐Cl)(Hpz^Ph)₃]₂ ( 1 ) and [CoCl₂(Hpz^Ph)₄] ( 2 ) were obtained by reaction of CoCl₂ with HC(pz^Ph)₃ and Hpz^Ph, respectively (Hpz^Ph=3‐phenylpyrazole). The compounds were isolated as air‐stable solids and fully characterized by IR and far‐IR spectroscopy, MS(ESI+/?), elemental analysis, cyclic voltammetry (CV), controlled potential electrolysis, and single‐crystal X‐ray diffraction. Electrochemical studies showed that 1 and 2 undergo single‐electron irreversible Co^II→Co^III oxidations and Co^II→Co^I reductions at potentials measured by CV, which also allowed, in the case of dinuclear complex 1 , the detection of electronic communication between the Co centers through the chloride bridging ligands. The electrochemical behavior of models of 1 and 2 were also investigated by density functional theory (DFT) methods, which indicated that the vertical oxidation of 1 and 2 (that before structural relaxation) affects mostly the chloride and pyrazolyl ligands, whereas adiabatic oxidation (that after the geometry relaxation) and reduction are mostly metal centered. Compounds 1 and 2 and, for comparative purposes, other related scorpionate and pyrazole cobalt complexes, exhibit catalytic activity for the peroxidative oxidation of cyclohexane to cyclohexanol and cyclohexanone under mild conditions (room temperature, aqueous H₂O₂). In situ X‐ray absorption spectroscopy studies indicated that the species derived from complexes 1 and 2 during the oxidation of cyclohexane (i.e., Ox‐ 1 and Ox‐ 2 , respectively) are analogous and contain a Co^III site. Complex 2 showed low in vitro cytotoxicity toward the HCT116 colorectal carcinoma and MCF7 breast adenocarcinoma cell lines.     

D,L‐Proline‐Catalyzed One‐Pot Synthesis of Pyrans and Pyrano[2,3‐c]pyrazole Derivatives by a Grinding Method under Solvent‐Free Conditions

D,L‐Proline was found to efficiently catalyze the one‐pot condensation of aromatic aldehydes, malononitrile, and dimedone (1,3‐cyclohexanedione or 3‐methyl‐1‐phenyl‐2‐pyrazolin‐5‐one) 2‐Amino‐3‐cycano‐4‐aryl‐7,7‐dimethyl‐5,6,7,8‐tetrahydrobenzo[b]pyrans and 6‐amino‐5‐cyano‐4‐aryl‐1,4‐dihydropyrano[2,3‐c]pyrazoles were synthesized by a grinding method under solvent‐free conditions. The reaction proceeded cleanly at room temperature to afford the products in good yields.     

Iodobenzene Diacetate Mediated Oxidation of N-Substituted Hydrazones of Chalcones: An Efficient Regioselective Synthesis of 1,3,5-Trisubstituted Pyrazoles

Iodobenzene diacetate, a relatively benign nonmetallic oxidant, has been utilized efficiently for the oxidation of N-substituted hydrazones of chalcones to afford 1,3,5-trisubstituted pyrazoles under mild reaction conditions.