Pyrazole Scaffold Research Articles

One-Pot Synthesis and Antiproliferative Activity of Highly Functionalized Pyrazole Derivatives.

A series of highly functionalized pyrazole derivatives has been prepared by a one-pot, versatile and regioselective procedure. Pyrazoles 1-29 were tested in cell-based assay to assess their antiproliferative activity against a panel of tumour cells. Additionally, the cytotoxicity of prepared compounds was evaluated against normal human fibroblasts. The antiproliferative activity of the synthesized molecules emerged to be affected by the nature of the substituents of the pyrazole scaffold and derivatives 21-23 proved to inhibit the growth of melanoma and cervical cancer cells. Compound 23 was identified as the most active derivative and docking simulations predicted its ability to interact with estrogen receptors.

Recent Progress in Anticancer Agents Incorporating Pyrazole Scaffold.

The search for new anticancer agents is considered a dynamic field of medicinal chemistry. In recent years, the synthesis of compounds with anticancer potential has increased and a large number of structurally varied compounds displaying potent anticancer activities have been published. Pyrazole is an important biologically active scaffold that possesses nearly all types of biological activities. The aim of this review is to collate literature work reported by researchers to provide an overview on in vivo and in vitro anticancer activities of pyrazole based derivatives among the diverse biological activities displayed by them and also to present recent efforts made on this heterocyclic moiety regarding anticancer activities. This review has been driven by the increasing number of publications on this issue, which have been reported in the literature since the end of the 20th century (from 1995-to date).

Synthesis of Spirooxindole Analogs Tethered Pyrazole Scaffold as Acetylcholinesterase Inhibitors

AbstractA new series of spirooxindole analogs tethered pyrazole scaffold constructed via [3+2] cycloaddition (32CA) reaction starting from the new chalcone named (E)‐3‐(5‐chloro‐3‐methyl‐1‐phenyl‐1H‐pyrazol‐4‐yl)‐1‐(5‐methyl‐1‐phenyl‐1H‐pyrazol‐4‐yl)prop‐2‐en‐1‐one which confirmed by single crystal X‐ray diffraction analysis. Synthesized spirooxindole analogs were evaluated for their neuroprotection through the inhibition of acetylcholine esterase enzyme using Ellman's method. Compounds 9 w, 9 e and 9 x showed the strongest acetylcholine esterase inhibition (AChEI) with IC50 values of 5.7, 7.8 and 8.3 μM, respectively. Obviously, the incorporation of NO2 group into isatin 5th position and N‐methylglycine (sarcosine) play a crucial role for the activity which lead to compound 9 w had the most potent inhibitory activity with IC50 value of 5.7 μM. Molecular docking was used to study their interaction with the active site of hAChE. These 32CA reactions takes place via a one‐step mechanism with a high polar character as a consequence of the supernucleophilic character of azomethine yildes and the strong electrophilic character of ethylenes.

Synthesis, DFT and Antitumor Activity Screening of Some New Heterocycles Derived from 2,2'-(2-(1,3-Diphenyl-1H-Pyrazol-4-yl)Ethene-1,1-Diyl)Bis(4H-Benzo[d][1,3]Oxazin-4-One)

The broad spectrum of biological activity of pyrazole derivatives coupled with our interest in the chemistry of nitrogen heterocycles led us to synthesize a bis-benzoxazinone derivative bearing a pyrazole scaffold and utilize it as a key material for the construction of some bisimidazole, bistriazole, and bisbenzimidazole derivatives obtained by reactions with some mono- and bidentate nitrogen nucleophiles. The density functional theory studies of the synthesized compounds were calculated. The synthesized compounds were screened for their in vitro antitumor activity against two human tumor cell lines; HepG2 and MCF-7. Some compounds displayed satisfactory activities.

Design, Synthesis, and Biological Evaluation of Pyrano[2,3-c]-pyrazole–Based RalA Inhibitors Against Hepatocellular Carcinoma

The activation of Ras small GTPases, including RalA and RalB, plays an important role in carcinogenesis, tumor progress, and metastasis. In the current study, we report the discovery of a series of 6-sulfonylamide-pyrano [2,3-c]-pyrazole derivatives as novel RalA inhibitors. ELISA-based biochemical assay results indicated that compounds 4k–4r suppressed RalA/B binding capacities to their substrates. Cellular proliferation assays indicated that these RalA inhibitors potently inhibited the proliferation of HCC cell lines, including HepG2, SMMC-7721, Hep3B, and Huh-7 cells. Among the evaluated compounds, 4p displayed good inhibitory capacities on RalA (IC50 = 0.22 μM) and HepG2 cells (IC50 = 2.28 μM). Overall, our results suggested that a novel small-molecule RalA inhibitor with a 6-sulfonylamide-pyrano [2, 3-c]-pyrazole scaffold suppressed autophagy and cell proliferation in hepatocellular carcinoma, and that it has potential for HCC-targeted therapy.

Construction of Spirooxindole Analogues Engrafted with Indole and Pyrazole Scaffolds as Acetylcholinesterase Inhibitors.

Twenty-five new hits of spirooxindole analogs 8a–y engrafted with indole and pyrazole scaffolds were designed and constructed via a [3+2]cycloaddition (32CA) reaction starting from three components: new chalcone-based indole and pyrazole scaffolds 5a–d, substituted isatins 6a–c, and secondary amines 7a–d. The potency of the compounds were assessed in modulating cholinesterase (AChE) activity using Ellman’s method. Compounds 8i and 8y showed the strongest acetylcholine esterase inhibition (AChEI) with IC50 values of 24.1 and 27.8 μM, respectively. Molecular docking was used to study their interaction with the active site of hAChE.

Regio- and stereoselective synthesis of spiro-heterocycles bearing the pyrazole scaffold via [3+2] cycloaddition reaction

Herein we reported the utility of one-pot multicomponent based [3+2] cycloaddition reaction transformation to prepare a new two hybrids of spirooxindoles engrafted with pyrazole skeleton. Upon treatment of the electron-deficient olefins based pyrazole motif with in situ the generated azomethine ylides (AY) of sarcosine with the 6-chloro-isatin afforded spiroadducts. To enlighten the regio- and diastereo-selectivity of these spiroheterocycles, single crystal X-ray diffraction analysis was presented. Using Hirshfeld calculations, many short distance contacts such as O…H, Cl…H, N…H, H…C, C…C and Cl…S have a great impact on the molecular packing and the crystal stability of 8a and 8b. The latter showed some Cl…Cl inter halogen interactions (Cl1…Cl3; 3.358 Å). In addition, DFT calculations were used to compute the electronic properties as well as the 1H- and 13C-NMR spectra of the studied systems. Both compounds are polar where 8b (3.995 Debye) has higher dipole moment than 8a (3.414 Debye). The NMR chemical shifts were calculated and found in excellent correlations between the calculated and experimental data were obtained (R2 = 0.94–0.98).

Synthesis of pyrazolo[1,5-a]pyrimidine ring as a possible bioisosteric replacement of the 5-(1H-pyrrol-1-yl)pyrazole scaffold

Synthesis of pyrazolo[1,5-a]pyrimidine ring as a possible bioisosteric replacement of the 5-(1H-pyrrol-1-yl)pyrazole scaffold

A new role for photoexcited Na2 eosin Y as direct hydrogen atom transfer (HAT) photocatalyst in photochemical synthesis of dihydropyrano[2,3-c]pyrazole scaffolds promoted by visible light irradiation under air atmosphere

Evidence indicates that Na2 eosin Y-derived photoexcited states functions as a direct hydrogen atom transfer (HAT) catalyst to synthesize dihydropyrano[2,3-c]pyrazole scaffolds photochemically via four-condensation domino reaction of tandem Knoevenagel-Michael cyclocondensation reaction ethyl acetoacetate, hydrazine hydrate, aryl aldehyde derivatives and malononitrile via visible light-mediated in aqueous ethanol at ambient temperature under air atmosphere. This study paves the new role for further the use of a metal-free organic dye with commercial availability and inexpensiveness, Na2 eosin Y in photochemical synthesis with use of the lowest amount of catalyst, excellent yields, time-saving aspects of the reaction and high atom economy. Notably, this cyclization is also runnable on the gram scale, which highlights the potentiality of using this reaction in industrial uses.

Substituted Imidazole-Pyrazole Clubbed Scaffolds: Microwave Assisted Synthesis and Examined Their In-vitro Antimicrobial and Antituberculosis Effects

A series of substituted imidazole-pyrazole fused compounds were designed & fused synthesized by employing Debus-Radziszewski one-pot synthesis reaction. Azoles are an extensive and comparatively new class of synthetic compounds including imidazoles and pyrazoles. The current clinical treatment uses compounds of azole framework. Azoles act by inhibiting ergosterol synthesis pathway (a principal component of the fungal cell wall). In addition, a literature review shows that the compounds that include imidazoles and pyrazoles have significant anti-bacterial and anti-mycobacterial effects. In light of the above findings, a series of compounds with imidazole and pyrazole scaffolds were sketched and developed to examine anti-bacterial, antifungal and antimycobacterial activities. The structures of the synthesized compounds were characterized using <sup>1</sup>HNMR, <sup>13</sup>CNMR, elemental analysis, and MS spectral data. The target compounds were screened for their in-vitro antimicrobial activity against gram-positive and gram-negative bacterial species by disc diffusion method according to the NCCLS (National Committee for Clinical Laboratory Standards) and anti-mycobacterial activity against the Mycobacterium tuberculosis H37Rv strain. The results revealed that imidazole-pyrazole fused scaffold compounds have potential antibacterial, antifungal and anti-mycobacterial activities which can be further optimized to get a lead compound.

Synthesis and Hypoglycemic Activity of the Derivatives of 4-(1,3-Thiazolidine-5-Ylidene)Pyrazole-3-Carbonic Acid and its Esters

A preparatively convenient method for synthesizing a series of new (pyrazole-4-yl)methylenethiazolidine structures fictionalized by the carboxylate or carboxylic group in the 3rd position of the pyrazole cycle and by the oxo- thio- or imine groups in the 3rd and 5th positions of the thiazolidine ring is discussed. The method is based on the condensation of 4-formylpyrazole-3-carbonic acids and their ethyl esters with a series of substituted thiazolidines: 1,3-thiazolidine-2,4-dione, 4-thioxo-1,3-thiazolidine-2-one, 2-thioxo-1,3-thiazolidine-4-one, and 2-imino-1,3-thiazolidine-4-one. As seen from the biochemical investigations results, a clear hypoglycemic activity has been registered for the compounds mentioned in this work. Five of ten products have ensured a prolonged effect embracing the entire duration of the experiment. 1-Methyl-4[(4-oxo-2-thioxo-1,3-thiazolidine-5-iliden)methyl]-1H-pyrazole-3-carbonic acid caused the deepest decrease in the glucose content (by 2.0 mmole/L or 30.4 %), while in the case of the reference medicine pioglitazone, it was only by 1.35 mmole/L (23.9 %). Some dependence between the compound structure and its pharmaceutical activity was also found. The most prolonged and steady hypoglycemic activity was registered for (pyrazole-4-il)methylethiazolidines with methyl group as a substitute in the 1st position and carboxylic group – in the 3rd position. The additional introduction of the methyl and carboxylate groups into the pyrazole scaffold results in a prolonged and more in-depth hypoglycemic effect leading to the 1.4 times lesser drop in glucose concentration as compared to that after administration of the reference medicine.

Synthesis and Functionalization of Coumarin-Pyrazole Scaffold: Recent Development, Challenges, and Opportunities.

Heterocycles are the main structural motif of DNA and RNA and play a crucial role in various chemical reactions of metabolisms. Therefore, heterocyclic compounds show good physiological and pharmacological properties. Coumarin and pyrazole scaffolds are present in many commercial drug molecules and natural products. This review overviews the progress made in the synthesis and functionalization of the coumarin- pyrazole hybrid heterocycle. It also includes discussion on the possible reactive sites of heterocycles, functionalization, and mechanistic pathways to incorporate pyrazole pharmacophore unit in synthesis. Several synthesis and biological studies reveal that the combination of the coumarin-pyrazole moiety is a prominent structural motif to find lead compounds in drug discovery.

Pyrazole Scaffold Synthesis, Functionalization, and Applications in Alzheimer's Disease and Parkinson's Disease Treatment (2011-2020).

The remarkable prevalence of pyrazole scaffolds in a versatile array of bioactive molecules ranging from apixaban, an anticoagulant used to treat and prevent blood clots and stroke, to bixafen, a pyrazole-carboxamide fungicide used to control diseases of rapeseed and cereal plants, has encouraged both medicinal and organic chemists to explore new methods in developing pyrazole-containing compounds for different applications. Although numerous synthetic strategies have been developed in the last 10 years, there has not been a comprehensive overview of synthesis and the implication of recent advances for treating neurodegenerative disease. This review first presents the advances in pyrazole scaffold synthesis and their functionalization that have been published during the last decade (2011–2020). We then narrow the focus to the application of these strategies in the development of therapeutics for neurodegenerative diseases, particularly for Alzheimer’s disease (AD) and Parkinson’s disease (PD).

AC-SO3H/[CholineCl][Urea]2 as a green catalytic system for the synthesis of pyrano[2,3-c]pyrazole scaffolds

A sulfonated amorphous carbon (AC-SO3H) was prepared from rice husk with sulfuric acid and fully characterized using FT-IR spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS). Deep eutectic solvent between choline chloride and urea was obtained from cheap and available material. The as-synthesized AC-SO3H was applied to prepare pyrano[2,3-c]pyrazoles through a four-component reaction of aromatic aldehydes, ethyl acetoacetate, hydrazines, and malononitrile with moderate to good yields in deep eutectic solvent at room temperature. The catalytic system was synthesized easily through a low-cost, non-toxic, eco-friendly, and simple procedure with potential application in large-scale process.

Selective functionalization of the 1H-imidazo[1,2-b]pyrazole scaffold. A new potential non-classical isostere of indole and a precursor of push-pull dyes.

We report the selective functionalization of the 1H-imidazo[1,2-b]pyrazole scaffold using a Br/Mg-exchange, as well as regioselective magnesiations and zincations with TMP-bases (TMP = 2,2,6,6-tetramethylpiperidyl), followed by trapping reactions with various electrophiles. In addition, we report a fragmentation of the pyrazole ring, giving access to push–pull dyes with a proaromatic (1,3-dihydro-2H-imidazol-2-ylidene)malononitrile core. These functionalization methods were used in the synthesis of an isostere of the indolyl drug pruvanserin. Comparative assays between the original drug and the isostere showed that a substitution of the indole ring with a 1H-imidazo[1,2-b]pyrazole results in a significantly improved solubility in aqueous media.

Pyrazole Incorporated New Thiosemicarbazones: Design, Synthesis and Investigation of DPP-4 Inhibitory Effects.

Dipeptidyl peptidase-4 (DPP-4) inhibition has been recognized as a promising approach to develop safe and potent antidiabetic agents for the management of type 2 diabetes. In this context, new thiosemicarbazones (2a–o) were prepared efficiently by the reaction of aromatic aldehydes with 4-[4-(1H-pyrazol-1-yl)phenyl]thiosemicarbazide (1), which was obtained via the reaction of 4-(1H-pyrazol-1-yl)phenyl isothiocyanate with hydrazine hydrate. Compounds 2a–o were evaluated for their DPP-4 inhibitory effects based on a convenient fluorescence-based assay. 4-[4-(1H-pyrazol-1-yl)phenyl]-1-(4-bromobenzylidene)thiosemicarbazide (2f) was identified as the most effective DPP-4 inhibitor in this series with an IC50 value of 1.266 ± 0.264 nM when compared with sitagliptin (IC50 = 4.380 ± 0.319 nM). MTT test was carried out to assess the cytotoxic effects of compounds 2a–o on NIH/3T3 mouse embryonic fibroblast (normal) cell line. According to cytotoxicity assay, compound 2f showed cytotoxicity towards NIH/3T3 cell line with an IC50 value higher than 500 µM pointing out its favourable safety profile. Molecular docking studies indicated that compound 2f presented π-π interactions with Arg358 and Tyr666 via pyrazole scaffold and 4-bromophenyl substituent, respectively. Overall, in vitro and in silico studies put emphasis on that compound 2f attracts a great notice as a drug-like DPP-4 inhibitor for further antidiabetic research.

Synthesis, antiproliferative activity, and molecular docking of some N‐heterocycles bearing a pyrazole scaffold against liver and breast tumors

AbstractA new series of some 1,3‐diphenylpyrazole‐based heterocycles were constructed from 2‐cyano‐3‐(1,3‐diphenyl‐1H‐pyrazol‐4‐yl)propenoyl chloride (1). The titled acid chloride was submitted to react with mono‐nucleophilic reagents, including oxygen, sulfur, or nitrogen, to afford new acrylate, thioacrylate, and acrylamide derivatives, respectively. Meanwhile, condensation of 1 with some 1,2‐ and 1,3‐binucleophiles led to the construction of oxadiazepine, pyridopyrimidine, and thiadiazolopyrimidine derivatives (16, 18, 20, 23). In turn, two benzoxazinone derivatives (27, 28) were synthesized upon treating 1 with substituted anthranilic acids followed by heating with acetic anhydride. The antiproliferative activity of the compounds developed against two tumors (HePG2 and MCF7) was evaluated. Compounds 4, 6, 11, 25, and 26 exhibited strong activity and compounds 3, 5, 16, 18, 27, and 28 exhibited moderate activity. A molecular modeling study was conducted by utilizing molecular modeling environment to test the binding free energies of the studied compounds toward human cyclin‐dependent kinase 2. The compounds, 4, 25, and 26, displayed the best docking score. The orientation and hydrogen bond pattern of these compounds in the active site correspond to that of PNU‐292137, which had been approved as a selective CDK2 inhibitor.

Discovery of trisubstituted pyrazolines as a novel scaffold for the development of selective phosphodiesterase 5 inhibitors

Celecoxib, is a selective cyclooxygenase-2 (COX2) inhibitor with a 1,5-diaryl pyrazole scaffold. Celecoxib has a better safety profile compared to other COX2 inhibitors having side effects of systemic hypertension and thromboembolic complications. This may be partly attributed to an off-target activity involving phosphodiesterase 5 (PDE5) inhibition and the potentiation of NO/cGMP signalling allowing coronary vasodilation and aortic relaxation. Inspired by the structure of celecoxib, we synthesized a chemically diverse series of compounds containing a 1,3,5-trisubstituted pyrazoline scaffold to improve PDE5 inhibitory potency, while eliminating COX2 inhibitory activity. SAR studies for PDE5 inhibition revealed an essential role for a carboxylic acid functionality at the 1-phenyl and the importance of the non-planar pyrazoline core over the planar pyrazole with the 5-phenyl moiety tolerating a range of substituents. These modifications led to new PDE5 inhibitors with approximately 20-fold improved potency to inhibit PDE5 and no COX-2 inhibitory activity compared with celecoxib. PDE isozyme profiling of compound 11 revealed a favorable selectivity profile. These results suggest that trisubstituted pyrazolines provide a promising scaffold for further chemical optimization to identify novel PDE5 inhibitors with potential for less side effects compared with available PDE5 inhibitors used for the treatment of penile erectile dysfunction and pulmonary hypertension.

Bronchospasmolytic and Adenosine Binding Activity of 8- (Proline / Pyrazole)- Substituted Xanthine Derivatives.

8-Phenyltheophylline derivatives exhibit prophylactic effects at a specific dose but do not produce the cardiovascular or emetic side effects associated with xanthines, thereby exhibiting unique characteristics of potential therapeutic importance. Novel series of 8-(proline/pyrazole)-substituted xanthine analogs have been synthesized. The affinity and selectivity of compounds to adenosine receptors have been assessed by radioligand binding studies. The synthesized compounds also showed good bronchospasmolytic properties (increased onset of bronchospasm; decreased duration of jerks) with 100% survival of animals in comparison to the standard drug. Besides, compound 8f & 9f showed good binding affinity in comparison to other synthesized compounds in the micromolar range. The maximum binding affinity of these compounds was observed for A2B receptors, which was ~ 7 or 10 times higher as compared to A1, A2A and A3 receptors. The newly synthesized derivatives 8f, 9a-f, 17g-m, and 18g-m displayed significant protection against histamine aerosol induced bronchospasm in guinea pigs. Newly synthesized proline/pyrazole based xanthines compounds showed a satisfactory binding affinity for adenosine receptor subtypes. Replacement or variation of substituted proline ring with substituted pyrazole scaffold at the 8th-position of xanthine moiety resulted in the reduction of adenosine binding affinity and bronchospasmolytic effects.

Discovery of biphenyl pyrazole scaffold for neurodegenerative diseases: A novel class of acetylcholinesterase-centered multitargeted ligands

Multitargeted ligands have demonstrated remarkable efficiency as potential therapeutics for neurodegenerative diseases as they target multiple pathways involved in the progression of these diseases. Herein, we report first-in-class dual inhibitor of acetylcholinesterase (AChE) and tau aggregation as a novel class of multitargeted ligands for neurodegenerative diseases. The reported biphenyl pyrazole scaffold binds monomeric tau with submicromolar affinity and impedes the formation of tau oligomers at early stages. Additionally, the lead compound inhibited AChE activity with an IC50 value of 0.35 ± 0.02 μM. Remarkably, the neuroprotective effect of this lead in induced cytotoxicity model of SH-SY5Y neuroblastoma cells is superior to single-targeted AChE and tau-aggregation inhibitors. This scaffold would enable development of new generation of multitargeted ligands for neurodegenerative diseases that function through dual targeting of AChE and monomeric tau.