Synthesis and biological activity of some new 1-benzyl and 1-benzoyl-3-heterocyclic indole derivatives

One pot synthesis of two potent Ag(I) complexes with quinoxaline ligand, X-ray structure, Hirshfeld analysis, antimicrobial, and antitumor investigations

In one pot, the self-assembly of AgNO₃ and 2-chloroquinoxaline (2Cl-quinox) in water-ethanol mixture afforded two novel crystalline Ag(I) complexes. The major product is the polymeric complex [Ag(2Cl-quinox)(NO₃)]_n; (1), while the minor product (2) comprises two molecules which are the monomeric [Ag(2Cl-quinox)₂(NO₃)]; (2a) and polymeric [Ag(2Cl-quinox)(NO₃)]_n; (2b) complexes. The single crystal X-ray structure revealed that 1 and 2b are made up of two-dimensional infinite sheets. In contrast, 2a is a monomeric complex which has a highly distorted tetrahedral geometry around Ag(I) center. In all cases, the 2Cl-quinox molecule acts as a terminal monodentate ligand. Complexes 1 and 2b have similar molecular structures and also have almost similar crystal packing. Using Hirshfeld surface analysis, the O…H hydrogen bonds and π-π stacking interactions contributed significantly to the molecular packing. Both complexes have broad-spectrum action towards multi drug-resistance bacteria. The most effective function of 2 is against Proteus morganii, with a MIC value of 8 μg/mL. Complex 2 (IC₅₀ = 5.93 ± 0.52 μg/mL) has remarkably greater cytotoxic effect against lung carcinoma (A-549) than cis-platin (IC₅₀ = 7.5 ± 0.69 μg/mL) and AgNO₃ (IC₅₀ = 14.7 ± 0.53 μg/mL). The higher Ag-content in 2 could be the main reason for its higher cytotoxicity than 1.

Multidrug-Resistant Biofilm, Quorum Sensing, Quorum Quenching, and Antibacterial Activities of Indole Derivatives as Potential Eradication Approaches

Challenges encountered in relapse of illness caused by resistance of microorganisms to antimicrobial agents (drugs) are due to factors of severe stress initiated by random use of antibiotics and insufficient beneficial approaches. These challenges have resulted to multiple drug resistance (MDR) and, subsequently, biofilm formation. A type of intercellular communication signal called quorum sensing (QS) has been studied to cause the spread of resistance, thereby enabling a formation of stable community for microorganisms. The QS could be inhibited using QS inhibitors (QSIs) called quorum-quenching (QQ). The QQ is an antibiofilm agent. Indole derivatives from plant sources can serve as quorum-quenching eradication approach for biofilm, as well as a promising nontoxic antibiofilm agent. In other words, phytochemicals in plants help to control and prevent biofilm formation. It could be recommended that combination strategies of these indoles' derivatives with antibiotics would yield enhanced results.

The Molecular Diversity of 1H-Indole-3-Carbaldehyde Derivatives and Their Role in Multicomponent Reactions

1H-Indole-3-carbaldehyde and related members of the indole family are ideal precursors for the synthesis of active molecules. 1H-Indole-3-carbaldehyde and its derivatives are essential and efficient chemical precursors for generating biologically active structures. Multicomponent reactions (MCRs) offer access to complex molecules. This review highlights the recent applications of 1H-indole-3-carbaldehyde in such inherently sustainable multicomponent reactions from the period, 2014 to 2021 and provides an overview of the field that awaits further exploitation in the assembly of pharmaceutically interesting scaffolds.

Imidazolidine Derivatives in Cancer Research: What is known?

Even though cancer is the second leading cause of death globally, a number of open issues persist in cancer treatment, despite the achievements of the field. This review aims at discussing the fundamental role of Imidazolidine derivatives in the industry of cancer treatment. Compelling data from 1996 to 2021 will introduce Imidazolidine derivatives as a relevant tool to modulate cancer progression.

Design, synthesis, molecular docking and ADME studies of novel indole-thiazolidinedione derivatives and their antineoplastic activity as CDK6 inhibitors

Several indole-thiazolidinedione derivatives (9–24) were designed and synthesized as CDK6 inhibitors, and their anticancer activity was probed on the MCF-7 cell line and the effects on gene expression profiles were elucidated.

Design, synthesis and anticancer/antiestrogenic activities of novel indole-benzimidazoles

Indole-benzimidazoles have recently gained attention due to their antiproliferative and antiestrogenic effects. However, their structural similarities and molecular mechanisms shared with selective estrogen receptor modulators (SERMs) have not yet been investigated. In this study, we synthesized novel ethylsulfonyl indole-benzimidazole derivatives by substituting the first (R₁) and fifth (R₂) positions of benzimidazole and indole groups, respectively. Subsequently, we performed ¹H NMR, ¹³C NMR, and Mass spectral and in silico docking analyses, and anticancer activity screening studies of these novel indole-benzimidazoles. The antiproliferative effects of indole-benzimidazoles were found to be more similar between the estrogen (E2) responsive cell lines MCF-7 and HEPG2 in comparison to the Estrogen Receptor negative (ER-) cell line MDA-MB-231. R₁:p-fluorobenzyl group members were selected as lead compounds for their potent anticancer effects and moderate structural affinity to ER. Microarray expression profiling and gene enrichment analyses (GSEA) of the selected compounds (R₁:p-fluorobenzyl: 48, 49, 50, 51; R₁:3,4-difluorobenzyl: 53) helped determine the similarly modulated cellular signaling pathways among derivatives. Moreover, we identified known compounds that have significantly similar gene signatures to that of 51 via queries performed in LINCS database; and further transcriptomics comparisons were made using public GEO datasets (GSE35428, GSE7765, GSE62673). Our results strongly demonstrate that these novel indole-benzimidazoles can modulate ER target gene expression as well as dioxin-mediated aryl hydrocarbon receptor and amino acid deprivation-mediated integrated stress response signaling in a dose-dependent manner.

Synthesis, crystal structures, antiproliferative activities and reverse docking studies of eight novel Schiff bases derived from benzil

Eight novel Schiff bases derived from benzil dihydrazone (BDH) or benzil monohydrazone (BMH) and four fused-ring carbonyl compounds (3-formylindole, FI; 3-acetylindole, AI; 3-formyl-1-methylindole, MFI; 1-formylnaphthalene, FN) were synthesized and characterized by elemental analysis, ESI-QTOF-MS, ¹H and ¹³C NMR spectroscopy, as well as single-crystal X-ray diffraction. They are (1Z,2Z)-1,2-bis{(E)-[(1H-indol-3-yl)methylidene]hydrazinylidene}-1,2-diphenylethane (BDHFI), C₃₂H₂₄N₆, (1Z,2Z)-1,2-bis{(E)-[1-(1H-indol-3-yl)ethylidene]hydrazinylidene}-1,2-diphenylethane (BDHAI), C₃₄H₂₈N₆, (1Z,2Z)-1,2-bis{(E)-[(1-methyl-1H-indol-3-yl)methylidene]hydrazinylidene}-1,2-diphenylethane (BMHMFI) acetonitrile hemisolvate, C₃₄H₂₈N₆·0.5CH₃CN, (1Z,2Z)-1,2-bis{(E)-[(naphthalen-1-yl)methylidene]hydrazinylidene}-1,2-diphenylethane (BDHFN), C₃₆H₂₆N₄, (Z)-2-{(E)-[(1H-indol-3-yl)methylidene]hydrazinylidene}-1,2-diphenylethanone (BMHFI), C₂₃H₁₇N₃O, (Z)-2-{(E)-[1-(1H-indol-3-yl)ethylidene]hydrazinylidene}-1,2-diphenylethanone (BMHAI), C₂₄H₁₉N₃O, (Z)-2-{(E)-[(1-methyl-1H-indol-3-yl)methylidene]hydrazinylidene}-1,2-diphenylethanone (BMHMFI), C₂₄H₁₉N₃O, and (Z)-2-{(E)-[(naphthalen-1-yl)methylidene]hydrazinylidene}-1,2-diphenylethanone (BMHFN) C₂₅H₁₈N₂O. Moreover, the in vitro cytotoxicity of the eight title compounds was evaluated against two tumour cell lines (A549 human lung cancer and 4T₁ mouse breast cancer) and two normal cell lines (MRC-5 normal lung cells and NIH 3T3 fibroblasts) by MTT assay. The results indicate that four (BDHMFI, BDHFN, BMHMFI and BMHFN) are inactive and the other four (BDHFI, BDHAI, BMHFI and BMHAI) show severe toxicities against human A549 and mouse 4T₁ cells, similar to the standard cisplatin. All the compounds exhibited weaker cytotoxicity against normal cells than cancer cells. The Swiss Target Prediction web server was applied for the prediction of protein targets. After analyzing the differences in frequency hits between these active and inactive Schiff bases, 18 probable targets were selected for reverse docking with the Surflex-dock function in SYBYL-X 2.0 software. Three target proteins, i.e. human ether-á-go-go-related (hERG) potassium channel, the inhibitor of apoptosis protein 3 and serine/threonine-protein kinase PIM1, were chosen as the targets. Finally, the ligand-based structure-activity relationships were analyzed based on the putative protein target (hERG) docking results, which will be used to design and synthesize novel hERG ion channel inhibitors.

Synthesis, Spectroscopic Identification and Molecular Docking of Certain N-(2-{[2-(1H-Indol-2-ylcarbonyl) Hydrazinyl](oxo)Acetylphenyl)Acetamides and N-[2-(2-{[2-(Acetylamino)Phenyl](oxo)Acetylhydrazinyl)-2-Oxoethyl]-1H-Indole-2-Carboxamides: New Antimicrobial Agents

N-(2-{[2-(1H-Indol-2-ylcarbonyl)hydrazinyl](oxo)acetyl}phenyl)acetamides (5a–h) and N-[2-(2-{[2-(acetylamino)phenyl](oxo)acetyl}hydrazinyl)-2-oxoethyl]-1H-indole-2-carboxamides (5i–l) were synthesized and characterized with different analytical tools. N-Acetylisatines 4a–d were subjected to ring opening at their C2 carbons with the aid of different indole-bearing hydrazides 3a,b and 7 to afford the respective glyoxylamides 5a–l. The antimicrobial activity of the target compounds 5a–l was assessed with the aid of Diameter of the Inhibition Zone (DIZ) and Minimum Inhibitory Concentration (MIC) assays against a panel of Gram-positive and Gram-negative bacteria and certain fungal strains. The antimicrobial screening revealed that Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, and Candida albicans are the most sensitive microorganisms towards the synthesized compounds 5a–l. In addition, compounds 5c and 5h emerged as the most active congeners towards Staphylococcus aureus and Candida albicans, respectively. Molecular docking studies revealed the possible binding mode of compounds 5c and 5h to their target proteins.

Synthesis, characterization and in vitro antimicrobial activity of novel fused pyrazolo[3,4-c]pyridazine, pyrazolo[3,4-d]pyrimidine, thieno[3,2-c]pyrazole and pyrazolo[3',4':4,5]thieno[2,3-d]pyrimidine derivatives

Background

Some novel substituted pyrazolone, pyrazolo[3,4-c]pyridazine, pyrazolo[3,4-d]pyrimidine, pyrazolo[3,4-d]thiazolo[3,2-a]pyrimidinone, thieno[3,2-c]pyrazole and pyrazolo[3′,4′:4,5]thieno[2,3-d]pyrimidine derivatives have been reported to possess various pharmacological activities like antimicrobial, antitumor and anti-inflammatory.

Results

A novel series of azoles and azines were designed and prepared via reaction of 1,3-diphenyl-1H-pyrazol-5(4H)-one with some electrophilic and nucleophilic reagents. The structures of target compounds were confirmed by elemental analyses and spectral data.

Conclusions

The antimicrobial activity of the target synthesized compounds were tested against various microorganisms such as Escherichia coli; Bacillus megaterium; Bacillus subtilis (Bacterial species), Fusarium proliferatum; Trichoderma harzianum; Aspergillus niger (fungal species) by the disc diffusion method. In general, the novel synthesized compounds showed a good antimicrobial activity against the previously mentioned microorganisms.

Synthesis, biological activity and molecular modeling study of new Schiff bases incorporated with indole moiety

A new series of heterocyclic Schiff bases 2-9 containing indole moiety were synthesized by facile and efficient condensation of indole-3/2/5-carboxaldehyde (1a/1b/1c) with different aromatic and heterocyclic primary amines using conventional and/or microwave irradiation methods. The structures of the obtained compounds were assigned by sophisticated spectroscopic and spectrometric techniques (1D-NMR, 2D-NMR and MS). The synthesized compounds were screened for their cytotoxicity and antibacterial activities. In vitro cytotoxicity screening revealed that compound 5 exhibited moderate activity against KB-3-1 cell line (IC50=57.7 μM) while 5-indolylimino derivative 7 indicated close to the activity (IC50=19.6 μM) in comparison with the positive control (+)-Griseofulvin (IC50=19.2 μM), while the tested compounds 5, 6b, 7 and 9 revealed good or moderate antibacterial activity. In addition, molecular docking study of Schiff bases 2-9 was performed by Molecular Operating Environment (MOE 2014.09) program on the matrix metalloproteinase-8 (MMP-8) (Protein Data Bank (PDB) ID: 1MNC) in an attempt to explore their mode of action as anticancer drugs.

Synthesis and biological activities of new bis-indole derivatives via microwave irradiation

Three new series of bis-indole derivatives were synthesized based on p-phenylenediamine (2–4, 5 and 6) and 4,4′-ethylenedianiline moieties (7–9) using facile and efficient condensation of three positional isomeric indole-carboxaldehyde derivatives (1a–c) with bifunctional amines upon microwave irradiation. The symmetric dimeric indole derivatives 2–4 as well as non-symmetric analogues 5 and 6 were obtained by in situ condensation of the respective positional 3-, 2- and 5-isomeric indole-carboxaldehydes with p-phenylenediamine, while compounds 7–9 resulted from respective condensation based on 4,4′-ethylenedianiline. Structures of the obtained compounds were deduced by advanced spectroscopic methods (1H NMR, 13C NMR and MS). In agar diffusion assay, derivative 6 showed moderate antibacterial activity against various Gram positive and negative bacteria, while derivative 7 displayed moderate activity against several Gram positive bacteria. However, in Resazurin assay employing the human cervix carcinoma cell line (KB-3-1), derivatives 2–9 turned out to be inactive.

Recent Advances in the Synthesis of Hydantoins: The State of the Art of a Valuable Scaffold

The review highlights the hydantoin syntheses presented from the point of view of the preparation methods. Novel synthetic routes to various hydantoin structures, the advances brought to the classical methods in the aim of producing more sustainable and environmentally friendly procedures for the preparation of these biomolecules, and a critical comparison of the different synthetic approaches developed in the last twelve years are also described. The review is composed of 95 schemes, 8 figures and 528 references for the last 12 years and includes the description of the hydantoin-based marketed drugs and clinical candidates.

Regiochemistry of cyclocondensation reactions in the synthesis of polyazaheterocycles

The syntheses of several polyazaheterocycles are demonstrated. The cyclocondensation reactions between β-enaminodiketones [CCl₃C(O)C(=CNMe₂)C(O)-CO₂Et] and aromatic amidines resulted in glyoxalate-substituted pyrido[1,2-a]pyrimidinone, thiazolo[3,2-a]pyrimidinone and pyrimido[1,2-a]benzimidazole. Pyrazinones and quinoxalinones were obtained through the reaction of these glyoxalates with ethylenediamine and 1,2-phenylenediamine derivatives. On the other hand, the reaction of glyoxalates with amidines did not lead to the formation of imidazolones, but rather N-acylated products were obtained. All the products were isolated in good yields. DFT-B3LYP calculations provided HOMO/LUMO coefficients, charge densities, and the stability energies of the intermediates, and from these data it was possible to explain the regiochemistry of the products obtained. Additionally, the data were a useful tool for elucidating the reaction mechanisms.

Crystal structure of 5-methoxy-N′-[(3Z)-1-benzyl-5-fluoro-2-oxo-1,2-dihydro-3H-indol-3-ylidene]-1H-indole-2-carbohydrazide-DMSO (1/1), C27H25FN4O4S

C27H25FN4O4S, triclinic, P1̅, a = 10.1996(5) Å, b = 11.4836(6) Å, c = 12.1907(8) Å, α = 100.728(2)°, β = 100.807(2)°, γ = 114.612(2)°, V = 1218.03(12) Å3, Z = 2, R gt (F) = 0.0542, wR ref (F 2 ) = 0.1319, T = 100 K.

Vibrational and electronic profiles, molecular docking and biological prediction of 5-methoxy-1-[(5-methoxy- 1H-indol-2-yl)methyl]-1H-indole: Experimental and theoretical investigations

Indole derivatives represent an important class of privileged structures. Spectroscopic (Fourier transform infrared (FT-IR), FT-Raman, 1H and [Formula: see text]C nuclear magnetic resonance (NMR)) investigations of the indole-bearing title compound, namely 5-methoxy-1-[(5-methoxy-1[Formula: see text]-indol-2-yl)methyl]-1[Formula: see text]-indole (MMIMI) have been carried out. The corresponding data of the MMIMI molecule were analyzed to understand its optimized geometry, and inter/intra-molecular interactions. The equilibrium geometry, harmonic vibrational wavenumbers, Frontier orbital energy, and natural bond orbital (NBO) analyses have been performed with the help of density functional theory (DFT) with B3LYP/6-311[Formula: see text]G([Formula: see text],[Formula: see text]) level of theory. The vibrational modes have been unequivocally assigned using potential energy distribution analysis. The theoretically predicted wavenumbers have good agreement with the experimental values. NBO has confirmed the intra-molecular charge transfer interactions. HOMO–LUMO analysis was carried out to explore charge delocalization on the MMIMI molecule. The immunomodulatory activity of the title molecule was predicted using molecular docking approach.

Synthesis, antimicrobial, antioxidant activities of novel 6-aryl-5-cyano thiouracil derivatives

A series of 6-aryl-5-cyano thiouracil derivatives (2a-c to 11a-c) was synthesized from 6-aryl-4-hydrazino-2-thioxo-1,2-dihydropyrimidine-5-carbonitriles (1a-c). The products were characterized by analytical and spectral data (IR, (1)H NMR, (13)C NMR and mass spectra). All compounds were screened for their in-vitro antibacterial and antifungal activities. Compounds 7a, 7g and 9a-c showed pronounced antimicrobial activity than standards. Some of the newly synthesized compounds were evaluated for antioxidant activity. Compounds 1c, 5c and 8c displayed promising free radical scavenging activity and found to be more potent than standard, ascorbic acid (vitamin C).

Synthesis, antimicrobial and anti-cancer activities of some new N-ethyl, N-benzyl and N-benzoyl-3-indolyl heterocycles

A series of 1-(N-substituted-1H-indol-3-yl)-3-arylprop-2-ene-1-ones (2a, b-4a, b) were prepared and allowed to react with urea, thiourea or guanidine to give pyrimidine derivatives 5a, b-13a, b. Reaction of 2a, b-4a, b with ethyl acetoacetate in the presence of a base gave cyclohexanone derivatives 14a, b-16a, b. Reaction of the latter compounds with hydrazine hydrate afforded indazole derivatives 17a, b-19a, b. On the other hand, reaction of 2a, b-4a, b with some hydrazine derivatives, namely hydrazine hydrate, acetyl hydrazine, phenylhydrazine and benzylhydrazine hydrochloride, led to the formation of pyrazole derivatives 20a, b-31a, b. Moreover, reaction of 2a, b-4a, b with hydroxylamine hydrochloride gave isoxazole derivatives 32a, b-34a, b. The newly synthesized compounds were tested for their antimicrobial activity and showed that 4-(N-ethyl-1H-indol-3-yl)-6-(p-chlorophenyl)-pyrimidine-2-amine (11b) was the most active of all the test compounds towards Candida albicans compared to the reference drug cycloheximide. Eighteen new compounds, namely pyrimidin-2(1H)-ones 5a, b-7a, b, pyrimidin-2(1H)-thiones 8a, b-10a, b and pyrimidin-2-amines 11a, b-13a, b derivatives, were tested for their in vitro antiproliferative activity against HEPG2, MCF7 and HCT-116 cancer cell lines. 4-(N-ethyl-1H-indol-3-yl)-6-(p-methoxyphenyl)-pyrimidin-2-amine (11a) was found to be highly active with IC(50) of 0.7 μmol L⁻¹.

Synthesis and potential biological activity of some novel 3-[(N-substituted indol-3-yl)methyleneamino]-6-amino-4-aryl-pyrano(2,3-c)pyrazole-5-carbonitriles and 3,6-diamino-4-(N-substituted indol-3-yl)pyrano(2,3-c)pyrazole-5-carbonitriles

Starting from N-substituted indole-3-carboxaldehydes (1a-g) a series of new 3-[(N-substituted indol-3-yl)methyleneamino]-6-amino-4-aryl-pyrano(2,3-c)pyrazole-5-carbonitriles (3a-g and 4a-g) have been synthesized via the acid catalyzed condensation reaction of 1a-g with 3-amino-5-pyrazolone, followed by the reaction with arylidene malononitriles. A series of new 3,6-diamino-4-(N-substituted indol-3-yl)pyrano(2,3-c)pyrazole-5-carbonitriles (7a-g) have been prepared either via the base catalyzed condensation reaction of 1a-g with 3-amino-5-pyrazolone to give 6a-g, followed by the reaction with malononitrile or by the reaction of N-substituted-3-indolylidene malononitriles (5a-g) with 3-amino-5-pyrazolone. According to the obtained results, the newly synthesized compounds possess significant anti-inflammatory, analgesic and anticonvulsant activities. The anticonvulsant potency of certain tested compounds was more pronounced than both anti-inflammatory and analgesic activities. Moreover, most of the newly synthesized compounds possess potential antimicrobial activity against Escherichia coli and Pseudomonas aeruginosa.

Synthesis, molecular docking study and antitumor activity of novel 2-phenylindole derivatives

The starting material, 4-(1-indol-2-yl)phenol 1 was obtained via Fischer synthesis. Vilsmeir Haack(')s formylation of 1 gave the carboxaldehyde derivative 2 which was subjected to different reactions affording the 3-substituted compounds 3-10. Compound 1 reacted with halo esters to give 11 and 12a,b. The reaction of 12a with various amino derivatives gave compounds 13-16. The hydrazide derivative 15a reacted with 1,3-diketones, ethyl acetoacetate and aromatic carboxylic acid derivatives to give 17a,b, 18 and 19a-e, respectively. Antitumor activity of target compounds were tested against breast cancer cell lines (MCF-7) and (MDA-MB-231). The most potent compound was 3e with IC(50) = 1.60 nM against (MCF-7). Docking was performed on colchicine binding site of tubulin to study the binding mode of the designed compounds.

InCl3 mediated one-pot multicomponent synthesis, anti-microbial, antioxidant and anticancer evaluation of 3-pyranyl indole derivatives

A simple and convenient method for the one-pot three-component synthesis of 3-pyranyl indoles has been accomplished by tandem Knoevenagel-Michael reaction of 3-cyanoacetyl indole, various aromatic aldehydes and malononitrile catalyzed by InCl(3) in ethanol under reflux conditions. The newly synthesized 3-pyranyl indoles were evaluated for anti-microbial, antioxidant, and anticancer activities. Some of the compounds showed good anticancer activity against MCF-7 breast cancer cell lines on comparison with of standard drug.