Indazole Derivatives Research Articles

Investigation on Photophysical, Solvatochromism and Biological Significance of Substituted 2H‐Indazole Derivatives

AbstractThe electronic properties of substituted 2H‐indazoles were investigated for their photophysical behavior under isolated conditions and in solvent environment, both computationally and experimentally. DFT calculations with CAM−B3LYP functional and 6–311++G** basis set were performed in the ground and excited states. The effect of solvents on the low and high energy electronic states was studied by following the steady state absorption and fluorescence excitation and emission spectra. Solvatochromic interactions including general and specific solvent effects are reported along with the results of Lippert and ET(30) plots. The biological significance of these 2H‐indazole derivatives was also investigated through docking studies. The interactions of 2H‐indazole derivatives with the active site of subdomain II of human casein kinase (C2 K) alpha are reported.

Different Strategies to the Synthesis of Indazole and its Derivatives: A Review

In this review, works of various researchers working on the synthesis of indazole and their related compound are cited. The review comprises of methodologies for the synthesis of 1H and 2H indazole derivatives, along with some pharmacological activities. In this review, research papers published in various peer-reviewed journals between the year 2000 and year 2017 are enlisted in alphabetical order.

Pd(PPh3)4 Catalyzed Synthesis of Indazole Derivatives as Potent Anticancer Drug

A series of 3-aryl indazoles and 1-methyl-3-aryl indazole derivatives are prepared with exceptional yields by coupling with several arylboronic acids and methylation by two dissimilar approaches. The as-prepared indazole derivatives (3a–3j) and their N-methyl derivatives (5a–5j) are evaluated for in vitro anticancer activity against two cancer cell lines, HCT-116 and MDA-MB-231. The results reveal that the indazole derivatives tested display mild to moderate anticancer activities against the cell lines tested.

Selected arylsulphonyl pyrazole derivatives as potential Chk1 kinase ligands\u2014computational investigations

Protein kinases control diversity of biochemical processes in human organism. Checkpoint 1 kinase (Chk1) is an important element of the checkpoint signalling pathways and is responsible for DNA damage repair. Hence, this kinase plays an essential role in cancer cells survival and has become an important target for anticancer agents. Our previous investigations showed that some arylsulphonyl indazole derivatives displayed anticancer effect in vitro. In the present study, in order to verify possibility of interactions of pyrazole and indazole derivatives with Chk1, we focused on the docking of selected tosyl derivatives of indazole and condensed pyrazole 1–7 to the Chk1 pocket, analysis of interactions involving optimized ligand–protein system using DFT formalism, and estimation of the interaction enthalpy of the ligand–protein complex by applying the PM7 method. The estimation of binding affinity seems to indicate that the indazole 5-substituted with 3,5-dimethylpyrazole 4 and condensed pyrazoloquinoline derivative 7 fit the best to the Chk1-binding pocket. The values of the energy of interaction, i.e. the enthalpy change (ΔHint), were between − 85.06 and − 124.04 kcal mol−1 for the optimized ligand–Chk1 complexes. The relaxation of the ligands within the complexes azole–protein as well as the distribution of hydrogen contacts between the ligands and kinase pocket amino acids was also analysed using molecular dynamics as a supporting method.Graphical Presentation of methods used to describe the interactions between arylsulphonyl pyrazole derivatives and Chk1 kinase

QSAR modeling, docking, ADME and reactivity of indazole derivatives as antagonizes of estrogen receptor alpha (ER-α) positive in breast cancer

To establish a quantitative structure-activity relationship, 54 indazole derivatives were analyzed by multiple linear regression MLR. The DFT-B3LYP method, with the basis set 6-311G, was performed to define the structure, chemical reactivity and properties of the compounds. This study was accompanied by molecular docking, global reactivity descriptors, absorption, distribution, metabolism and elimination (ADME) properties on a series of 21 compounds of selective estrogen receptor degraders (SERDs) that present the most active compounds from the dataset. The MLR regression equation displayed a good agreement between fitted and observed biological activities. A high average R2Boots greater than 0.5 indicates that the obtained model has good predictive power and robustness. In addition, an average value of R2pred (0.57) approximately equal to 0.6 may be taken as an indicator of good external predictability. The interactions between the most active compounds from the indazole series and ERα targets were explored through a molecular docking to elucidate the binding mode between the studied compounds and corresponding protein. Based on this study compounds 14, 43, 8 and 45 have no violated Lipinski’s rule of five and Veber’s rule, suggesting that these compounds would not have problems with oral bioavailability. Most of global reactivity results have an agreement with those obtained in this docking study.

Novel Azoles as Antiparasitic Remedies against Brain-Eating Amoebae.

Balamuthia mandrillaris and Naegleria fowleri are opportunistic protozoan pathogens capable of producing infection of the central nervous system with more than 95% mortality rate. Previously, we have synthesized several compounds with antiamoebic properties; however, synthesis of compounds that are analogues of clinically used drugs is a highly desirable approach that can lead to effective drug development against these devastating infections. In this regard, compounds belonging to the azole class possess wide range of antimicrobial properties and used clinically. In this study, six novel benzimidazole, indazole, and tetrazole derivatives were synthesized and tested against brain-eating amoebae. These compounds were tested for their amoebicidal and static properties against N. fowleri and B. mandrillaris. Furthermore, the compounds were conjugated with silver nanoparticles and characterized. The synthetic heterocyclic compounds showed up to 72% and 65% amoebicidal activities against N. fowleri and B. mandrillaris respectively, while expressing up to 75% and 70% amoebistatic activities, respectively. Following conjugation with silver nanoparticles, amoebicidal activities of the drugs increased by up to 46 and 36% versus B. mandrillaris and N. fowleri. Minimal effects were observed when the compounds were evaluated against human cells using cytotoxicity assays. In summary, azole compounds exhibited potent activity against N. fowleri and B. mandrillaris. Moreover, conjugation of the azole compounds with silver nanoparticles further augmented the capabilities of the compounds against amoebae.

A mild and readily scalable procedure for the N-1-difluoromethylation of ethyl 6-((tert-butyldiphenylsilyl)oxy)-1H-indazole-3-carboxylate and its applications to the N-difluoromethylation of indazole, benzotriazole, imidazole, indole and pyrazole derivatives

A set of mild conditions for the N-1-difluoromethylation of ethyl 6-((tert-butyldiphenylsilyl)oxy)-1H-indazole-3-carboxylate (1) with chlorodifluoromethane (CHClF2) on large scale (up to 33 g) is described. An optimized N-1-difluoromethylation of the functionalized indazole 1 was achieved, under an atmosphere of CHClF2 (balloon) in the presence of NaH and catalytic amounts of NaI and 18-crown-6 ether at a moderate temperature (40 °C). This procedure provides a safe and convenient alternative to existing approaches that require high pressures and/or the use of NaH in DMF at high temperatures that would present a safety concern when operating on a large scale. This method was extended to the N-difluoromethylation of indazole, benzotriazole, imidazole, indole and pyrazole derivatives, all of which bear an ester group.

1-(3-Amino-4-morpholino-1H-indazole-1-carbonyl)-N-phenylcyclopropane-1-carboxamide: Design, synthesis, crystal structure, antitumor activity, DFT and Hirshfeld surface analysis

An indazole derivative, 1-(3-amino-4-morpholino-1H-indazole-1-carbonyl)-N-phenylcyclopropa ne-1-carboxamide (C22H23N5O3, Mr = 405.45) has been synthesized by condensation of 1-(phenylcarbamoyl)cyclopropane-1-carboxylic acid with 4-morpholino-1H-indazol-3-amine, which was prepared from 2,6-difluorobenzonitrile by amination with morpholine and then cyclisation with hydrazine hydrate. Spectro-elemental characterizations and single-crystal X-ray analysis were done for the structure elucidation. C22H23N5O3 has a monoclinic system, space group P21/c with a = 10.427(2) Å, b = 17.283(4) Å, c = 13.759(2) Å, α = 90°, β = 122.773(12) °, γ = 90°. The optimized geometric bond lengths and bond angles obtained by using density functional theory (DFT) have been compared with X-ray diffraction values. The calculated HOMO - LUMO energy gap and electrostatic potential map were computed by DFT and reaction sites in the molecule are represented in molecular electrostatic potential maps (MEP) plot. The molecular electrostatic potential (MEP) surface map of the related molecule were investigated with theoretical calculations at the B3LYP/6-31G(d,p) levels. A quantitative analysis of the intermolecular interactions in the crystal structures has been performed using Hirshfeld surface analysis. In addition, the compound possesses distinct effective inhibition on the proliferation of HT-29, K562 and MKN45 cancer cell lines.

Regioselective C-H Sulfonylation of 2H-Indazoles by Electrosynthesis.

This study reveals a transition-metal- and external oxidant-free electrochemical method for the C3-H sulfonylation of biologically diverse 2H-indazoles at room temperature and under ambient air. Using various sulfonyl hydrazides as the sulfonyl precursor, a series of sulfonylated indazole derivatives containing a broad spectrum of functional groups were synthesized in up to 92% yield. Mechanistic studies suggest a precedented radical pathway is operating in the electrochemical process.

An efficient strategy for the preparation of insensitive energetic materials: intramolecular cyclization of picrylhydrazone into an indazole derivative

An efficient method to acheive a balance of energy and sensitivity through the intramolecular cyclization reaction of picrylhydrazone into an indazole derivative.

Copper-catalyzed cascade C–N coupling/C–H amination: one pot synthesis of imidazo[1,2-b]indazole

A one-pot, two-fold C–N bond formation protocol has been developed for the construction of imidazo[1,2-b]indazole derivatives.

The discovery of novel indazole derivatives as tubulin colchicine site binding agents that displayed potent antitumor activity both in vitro and in vivo

Tubulin inhibitors that bind to the colchicine site are widely studied anticancer agents. In continuous our researches, we designed a series of novel indazole derivatives as microtubule-targeting agents (MTAs). The structure-activity relationships (SARs) investigations indicated that a 3,4,5-trimethoxyphenyl moiety and a methyl or methoxy substitution were preferred for the better antiproliferative activity. The indazole derivatives 3c and 3f showed noteworthy low nanomolar potency against HepG2, HCT116, SW620, HT29 and A549 tumor cells. In mechanism studies, 3c and 3f were proved to target the colchicine site, inhibited tubulin polymerization and disrupted cellular microtubule networks, arrested HCT116 cell in G2/M phase and induced cell apoptosis. In the HCT116 xenografts mouse model, 3c and 3f suppressed tumor growth by 45.3% and 58.9% at an orally dose of 25 mg/kg without causing obvious weight loss. The indazole 3f may serve as a good lead or drug candidate for colorectal cancer therapy.

Design and Synthesis of New 6-Nitro and 6-Amino-3,3a,4,5-Tetrahydro-2H-Benzo[g]indazole Derivatives: Antiproliferative and Antibacterial Activity.

New substituted benzo[g]indazoles functionalized with a 6-nitro and 6-amino groups have been synthesized by the reaction of benzylidene tetralones with hydrazine in acetic acid. The resulting conformationally-constrained compounds were evaluated for their antiproliferative activity against selected cancer cell lines. The nitro-based indazoles 11a, 11b, 12a and 12b have shown IC50 values between 5–15 μM against the lung carcinoma cell line NCI-H460. Moreover, the nitro compounds were tested for antibacterial activity where compounds 12a and 13b have shown MIC values of 250 and 62.5 μg/mL against N. gonorrhoeae with no hemolytic activity in human red blood cells (RBC).

Design, synthesis and biological evaluation of novel 1H-1,2,4-triazole, benzothiazole and indazole-based derivatives as potent FGFR1 inhibitors viafragment-based virtual screening

Fibroblast growth-factor receptor (FGFR) is a potential target for cancer therapy. We designed three novel series of FGFR1 inhibitors bearing indazole, benzothiazole, and 1H-1,2,4-triazole scaffold via fragment-based virtual screening. All the newly synthesised compounds were evaluated in vitro for their inhibitory activities against FGFR1. Compound 9d bearing an indazole scaffold was first identified as a hit compound, with excellent kinase inhibitory activity (IC50 = 15.0 nM) and modest anti-proliferative activity (IC50 = 785.8 nM). Through two rounds of optimisation, the indazole derivative 9 u stood out as the most potent FGFR1 inhibitors with the best enzyme inhibitory activity (IC50 = 3.3 nM) and cellular activity (IC50 = 468.2 nM). Moreover, 9 u also exhibited good kinase selectivity. In addition, molecular docking study was performed to investigate the binding mode between target compounds and FGFR1.

Synthesis and evaluation of a novel series of 6-bromo-1-cyclopentyl-1H-indazole-4-carboxylic acid-substituted amide derivatives as anticancer, antiangiogenic, and antioxidant agents

A series of novel indazole derivatives has been synthesized and evaluated for anticancer, antiangiogenic, and antioxidant activities. The capability of the synthesized compounds 11a–x to hinder the viability of three human cancer cells lines, HEP3BPN 11 (liver), MDA 453 (breast), and HL 60 (leukemia), were assessed by using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) reduction assay. Among the compounds 11a–x screened, 11c and 11d showed the higher inhibitory activity on the viability of HEP3BPN 11 (liver), when compared with the standard methotrexate. These compounds were further tested to evaluate their potential to inhibit the proangiogenic cytokines associated with tumor development. Compound 11c was found to be a potent antiangiogenic agent against TNFα, VEGF, and EGF, whereas 11d showed potent antiangiogenic activity against TNFα, VEGF, IGF1, TGFb, and leptin inhibition. All the compounds 11a–x were screened for their antioxidant activities using 2,2-diphenyl-1-picryl hydrazine (DPPH), hydroxyl (OH), and superoxide radical (SOR) scavenging activity. Compounds 11n, 11p, 11q, and 11v have shown significant OH radical scavenging activities, also compounds 11c, 11h, and 11k were found to have a DPPH radical scavenging activity and compounds 11a and 11m exhibited better SOR scavenging activity when compared with the reference compound ascorbic acid. In silico molecular docking analysis revealed important structural insights behind observed anti TNFα effect by present indazole compounds.

The anti-inflammatory agent bindarit acts as a modulator of fatty acid-binding protein 4 in human monocytic cells

We investigated the cellular and molecular mechanisms by which bindarit, a small indazolic derivative with prominent anti-inflammatory effects, exerts its immunoregulatory activity in lipopolysaccharide (LPS) stimulated human monocytic cells. We found that bindarit differentially regulates the release of interleukin-8 (IL-8) and monocyte chemoattractant protein-1 (MCP-1), enhancing the release of IL-8 and reducing that of MCP-1. These effects specifically required a functional interaction between bindarit and fatty acid binding protein 4 (FABP4), a lipid chaperone that couples intracellular lipid mediators to their biological targets and signaling pathways. We further demonstrated that bindarit can directly interact with FABP4 by increasing its expression and nuclear localization, thus impacting on peroxisome proliferator-activated receptor γ (PPARγ) and LPS-dependent kinase signaling. Taken together, these findings suggest a potential key-role of FABP4 in the immunomodulatory activity of bindarit, and extend the spectrum of its possible therapeutic applications to FABP4 modulation.

Facile CuCl2·2H2O catalyzed one-pot conversion of dimedone into highly functionalized indazole based N-arylhydrazinecarbothioamides

A convenient and facile CuCl2·2H2O catalyzed one-pot synthetic strategy was designed for the conversion of readily available dimedone into highly functionalized N-arylhydrazinecarbothioamide based indazole derivatives. The product yields were found to be moderate to good without purification requirements. Structural features of the synthetic compounds were confirmed by various spectroscopic techniques such as 1H NMR, 13C NMR, EI-MS, FAB-MS, HREI-MS, and HRFAB-MS. The reaction intermediates were also quenched and characterized. Plausible reaction mechanisms were also discussed.

Synthetic Strategy for Pyrazolo[1,5-a]pyridine and Pyrido[1,2-b]indazole Derivatives through AcOH and O2-Promoted Cross-dehydrogenative Coupling Reactions between 1,3-Dicarbonyl Compounds and N-Amino-2-iminopyridines.

An efficient method has been developed for the synthesis of uniquely substituted pyrazolo[1,5-a]pyridine and pyrido[1,2-b]indazole derivatives, which involves acetic acid and molecular oxygen promoted cross-dehydrogenative coupling reactions of respective β-ketoesters and β-diketones (like ethyl acetoacetate, ethyl benzoylacetate, methyl propionylacetate, acetylacetone, dimedone, 1,3-cyclohexanedione, and 1,3-cyclopentanedione) with N-amino-2-iminopyridines. The proposed tentative mechanism involves formal acetic acid-promoted oxidative C(sp3)–C(sp2) dehydrogenative coupling followed by dehydrative cyclization under a catalyst-free condition within high atom economy processes.

Correlation of indoleamine-2,3-dioxigenase 1 inhibitory activity of 4,6-disubstituted indazole derivatives and their heme binding affinity.

Indoleamine 2,3-dioxygenase 1 (IDO1) is a heme-containing enzyme that acts on the first and rate-limiting step of the tryptophan/kynurenine pathway. Since the pathway is one of the means of cancer immune evasion, IDO1 inhibitors have drawn interest as potential therapeutics for cancers. We found a 4,6-disubstituted indazole 1 as a hit compound that showed both IDO1 inhibitory activity and binding affinity for IDO1 heme. Structural modification of 1 yielded compound 6, whose relatively large substituent at the 4-position and proper size substituent at the 6-position were found to be important for the enhancement of IDO1 inhibitory activity and heme affinity. A series of compounds synthesized in this work were evaluated by in silico docking simulations and by in vitro experiments using a C129Y mutant of the pocket-A of IDO1. Our results revealed that proper substituents at the 6- and 4-positions of the compounds interact with pockets A and B, respectively, and that, in particular, a good fit in pocket-A is important for the compounds' biological activities. Absorption spectral analysis of these compounds showed that they strongly bound to the ferrous heme rather than its ferric heme. Furthermore, we observed that the heme affinities of these compounds strongly correlate with their IDO1 inhibitory activities.

Decarboxylative Coupling Reaction of 2‐(1H‐Indol‐3‐yl)acetic Acids with Indole, Azaindole, Benzimidazole and Indazole Derivatives

Abstract3,3′‐Diindolylmethanes (DIMs) are an important class of indole alkaloids that exhibit anti‐inflammatory and anti‐cancer effects. Herein, we report on a new, mild and efficient copper(II)‐promoted decarboxylative coupling reaction of 2‐(1H‐indol‐3‐yl)acetic acid derivatives (1 a–h) with a variety of (substituted) indoles (2 a–t) yielding (un)symmetrically substituted DIMs (3 a–z, 3 aa–ai). Reaction of 2‐(1H‐indol‐3‐yl)acetic acid (1 a) with 7‐azaindole led to the 3,3′‐connected DIM analog 5 d, while 4‐, 5‐, and 6‐azaindoles and benzimidazole reacted at the N1‐nitrogen atom. Reaction of 1 a with 1H‐indazoles led to a mixture of 1‐ and 2‐substituted indazole derivatives. The new method allows large‐scale synthesis of biologically active DIMs.magnified image