An insight into the medicinal perspective of synthetic analogs of indole: A review

Exploring indole-dihydropyrimidinone derivatives: Design, synthesis, biological assessment, SAR analysis, and evaluation of mode of action in experimental visceral leishmaniasis

The emergence of drug resistance and the non-availability of vaccines encouraged us to identify novel chemical scaffolds as new anti-leishmanial agents. In doing so, a series of thirty-four indole-dihydropyrimidinone hybrid compounds were synthesized using the Biginelli multicomponent reaction. These synthesized compounds were tested against L. donovani in vitro and in vivo in experimental golden hamster model of visceral leishmaniasis. Compounds 4f and 4m were found to have promising anti-leishmanial properties against intracellular amastigotes (IC504.54 & 5.05 μM, respectively) with minimal cytotoxicity against J774.1 macrophage. 4f and 4m were tested in vivo, and only 4f effectively cleared the parasite burden (>65 %) in infected golden hamsters. Mode of action studies discloses that 4f induces oxidative stress-mediated mitochondrial dysfunction and impairment of ATP production and triggers apoptosis. SAR and PK studies revealed that compound 4f (indole-dihydropyrimidinone hybrid) may be used as a lead for developing future chemotherapeutic options for VL.

Amino acid- and peptide-conjugated heterocyclic compounds: A comprehensive review of Synthesis Strategies and biological activities

Amino acids and peptides have long been recognized as promising candidates for therapeutic development due to their unique structural properties and high specificity. However, their clinical application is often limited by rapid enzymatic degradation, poor bioavailability, and suboptimal pharmacokinetics. Conjugating these biomolecules with heterocyclic compounds has emerged as a transformative strategy to enhance their stability, bioavailability, and overall therapeutic efficacy. This review highlights significant advancements since 2000 in the synthesis and biological applications of amino acid- and peptide-conjugated heterocyclic compounds These conjugates are categorized based on their nitrogen-, sulfur-, and oxygen-containing heterocyclic cores. Key synthetic methodologies, including amide bond formation, carbon-heteroatom coupling, and carbon-carbon bond formation, are discussed in detail. These conjugates exhibit enhanced pharmacological properties, with notable applications in antimicrobial, anticancer, and anti-inflammatory treatments. Despite these advancements, challenges such as synthetic complexity and potential toxicity remain. Future research should prioritize refining synthetic methodologies and leveraging underexplored heterocycles to unlock broader therapeutic applications. Peptide-heterocycle conjugates represent a promising approach to overcoming persistent challenges in modern drug development.

Synthesis of 2-CF3-indoles or 2-CF3-indolin-3-ones via anaerobic or aerobic reactions of N-phenylpyridin-2-amines with TFISYs

Presented herein is a condition-controlled selective synthesis of 2-CF3-indoles or 2-CF3-indolin-3-ones based on the anaerobic or aerobic reaction of N-phenylpyridin-2-amines with trifluoromethyl imidoyl sulfoxonium ylides (TFISYs). This work not only discloses a novel reaction mode of TFISYs, but also provides a robust protocol for the effective functionalization of aniline derivatives leading to the concise and selective assembly of indole-related scaffolds bearing a pharmaceutically privileged CF3 unit.

Exploring N-heterocyclic linked novel hybrid chalcone derivatives: synthesis, characterization, evaluation of antidepressant activity, toxicity assessment, molecular docking, DFT and ADME study

In the search for novel antidepressant agents, twelve novel nitrogen-containing heterocycle-linked chalcone derivatives have been synthesized and comprehensively characterized using FT-IR, 1H NMR, 13C NMR, and Mass spectral methods. The synthetic strategy involves the preparation and optimization of reaction conditions for obtaining 4-carbazole-, indole-, and pyrrole-linked acetophenones, which were subsequently coupled with pyrazole aldehydes bearing piperidine, morpholine, benzotriazole, and imidazole ring systems. In vivo antidepressant activity of the compounds was evaluated using the Tail Suspension Test (TST) and Forced Swim Test (FST). Chalcone derivatives with a benzo[d][1,2,3]triazol-1-yl substituent exhibited significant reductions in immobility times, indicating enhanced antidepressant activity. Chalcone derivatives with piperidin-1-yl and morpholino groups demonstrated relatively lower activity. Molecular docking studies against the human serotonin transporter (hSERT) (PDB code: 5I6X) revealed that the chalcone derivatives exhibited excellent binding affinity (average docking score: -8.540, binding energy: -60.044 kcal mol-1) through favorable van der Waals, electrostatic, and hydrogen bonding interactions (only for 13b) within the active site. The binding interaction of compound 13b was particularly strong, with a Glide docking score of -9.120 and binding energy of -65.454 kcal mol-1, highlighting the contribution of both π-π stacking and hydrogen bonding interactions. Chalcone derivatives showed low acute oral toxicity (LD50 > 2000 mg kg-1, category 5) in female Swiss albino mice per OECD 423 guidelines, with no mortality or adverse effects at 300 and 2000 mg kg-1, and normal body weight gain over 14 days. These findings underscore the potential of benzo[d][1,2,3]triazol-1-yl-based chalcone derivatives as promising antidepressant agents with a favorable safety profile. Density Functional Theory (DFT) analysis was performed on the most active compound, 13c, to gain insights into its structural and electronic properties. Additionally, ADME (Absorption, Distribution, Metabolism, and Excretion) profiling of the synthesized compounds indicated favorable drug-like characteristics and balanced pharmacokinetic profiles, supporting their potential as promising candidates for further pharmaceutical development.

Recent advances in the synthesis of Glycoconjugated heterocycles: A promising strategy for accessing bioactive compounds

Glycoconjugation of biologically relevant heterocycles and natural products to create glycohybrids, combining the unique features of both structures, has emerged as a promising approach for the creation of carbohydrate-based therapeutics. This review presents a comprehensive overview of the glyco-heterocycles synthesized primarily over the past decade, offering in-depth insights into the synthetic methods employed. Additionally, the review delves into the biological activities exhibited by these molecules, with particular emphasis on the structural elements that influence their therapeutic potential. It covers the molecular hybridization of biologically privileged heterocycles-including thiadiazole, oxadiazole, pyrazole, imidazole, thiazolidine, pyridine, pyrimidine, indole, benzimidazole, benzothiazole, coumarin, quinoline, etc. with carbohydrates and explores their biological activity. By integrating insights into both synthetic strategies and bioactivity, this work aims to enhance the understanding of glyco-heterocycles as a versatile class of compounds for medicinal chemistry and drug development.

In vitro and in silico analysis of synthesized N-benzyl indole-derived hydrazones as potential anti-triple negative breast cancer agents

Triple-negative breast cancer (TNBC) is one of the most aggressive forms of breast cancer, and it is characterized by a high recurrence rate and the rapid development of drug resistance across various subtypes. Currently, there is no targeted therapy, which is specifically approved for the treatment of TNBC. In this study, we synthesized a series of N-benzyl indole-3-carboxaldehyde-based hydrazones and subjected them to in vitro anticancer studies on MCF-10A and MDA-MB-231 breast cancer (BC) cell lines. Our in vitro results suggested that all the compounds exhibited significant anti-TNBC activity, especially on MDA-MB-231 cells. Compound 5b showed excellent activity on MDA-MB-231 (IC50 = 17.2 ± 0.4 nM). Furthermore, molecular docking analysis revealed that this compound had a higher binding affinity towards the target EGFR (epidermal growth factor receptor) with a docking score of -10.523 kcal mol-1. The molecular dynamics simulation of complex 5b:3W2S showed stable binding over a period of 100 ns. A detailed multi-linear regression (MLR) QSAR denoted the importance of key molecular descriptors, such as com_accminus_2A, fringNlipo6A, and sp3Cplus_AbSA. These analyses indicate that the synthesized compounds deserve further studies for developing novel and more potent candidates against triple-negative breast cancer.

The formation reaction of a carbon-carbon bond promoted by Eosin-Y under visible light

In recent years, photochemical organic conversion promoted by visible light has attracted the interest of many organic chemists. Compared with traditional methods, visible light for the photoredox catalysis of renewable energy has been proved to be a mild and powerful tool that can promote the activation of organic molecules through the single electron transfer (SET) process. Therefore, the formation reaction of a C-C bond can be achieved by activating these molecules with visible light, which can effectively modify the structure of these compounds and obtain compounds with multiple structures and functions. At present, this research has become an important research field in organic synthesis. Eosin-Y, a cheap and widely-used organic dye, has been employed as an economically and environmentally friendly substitute for many transition-metal-based photocatalysts. In recent years, it has gained much more attention due to its ease of handling and eco-friendliness, and it has great potential for applications in visible-light-mediated organic synthesis. This article reviews the research results on the formation of carbon-carbon bonds promoted by the organic photocatalyst Eosin-Y under visible light in recent years, and discusses representative examples and their different mechanistic pathways (such as SET, HAT, and energy transfer).

C3 versus C5 Regioselectivity in the Intramolecular Dehydrative Friedel-Crafts Alkylation of Indole C4-Tethered Carbinols

Described herein is a mild catalytic dehydrative Friedel-Crafts alkylation of 1,1-diarylalkanols─a challenging reaction with exceedingly rare previous success, presumably because of the unfavorable steric hindrance around the reactive centers and the competitive E1 reaction. Executing in an intramolecular fashion and benefiting from the high nucleophilicity of indole, we have successfully utilized this reaction in synthesizing 3,4-fused indoles. Interestingly, the Friedel-Crafts alkylation strategy could also be applied to access 4,5-fused indoles via modification of the tether connecting the alcohol and indole moieties.

In vitro inhibitory activity of indole alkaloid derivatives against porcine epidemic diarrhea virus

Porcine epidemic diarrhea virus (PEDV) is an enteric coronavirus that can cause acute diarrhea, vomiting, dehydration, and high mortality of newborn piglets, leading to huge economic losses to the world pig industry. Given the limited efficacy of current PEDV vaccines, there is an urgent need for the development of antiviral drugs. In this study, the antiviral effects of 17 synthesized indole alkaloid derivatives against PEDV were investigated. It was observed that indole alkaloid derivative no. 14 exhibited significant inhibition of PEDV replication in a dose-dependent manner. Furthermore, time-of-addition assays and quantitative real-time PCR (QPCR) showed that delayed administration of this compound resulted in a weaker inhibitory effect on PEDV compared to early treatment. Mechanistic analysis revealed that this compound exerts its inhibitory effects during the entry stage of the PEDV life cycle. This study demonstrates the anti-PEDV effects of indole alkaloid derivative no. 14, suggesting its potential as a candidate drug for treating PEDV infections.

Design, synthesis and biological evaluation of novel 1H-indole-3-carbonitrile derivatives as potent TRK Inhibitors

Tropomyosin receptor kinase (TRK) has emerged as a promising therapeutic target in cancers driven by NTRK gene fusions. Herein, we report a highly potent TRK inhibitor, C11, developed using bioisosteric replacement and computer-aided drug design (CADD) strategies. Compound C11 demonstrated significant antiproliferative effects against TRK-dependent cell lines (Km-12), and exhibited a dose-dependent inhibition of both colony formation and cell migration. Mechanistic study revealed that C11 induced cancer cell death by arresting the cell cycle, triggering apoptosis, and reducing phosphorylated TRK levels. In vitro stability assays showed that compound C11 possessed excellent plasma stability (t1/2 > 480 min) and moderate liver microsomal stability (t1/2 = 38.9 min). Pharmacokinetic evaluation further indicated an oral bioavailability of 15.2 % for compound C11. These results highlight compound C11 as a promising lead compound for the further development of TRK inhibitors.

Design, synthesis, and biological evaluation of steroidal indole derivatives as membrane-targeting antibacterial candidates

Rational modification of natural products plays a key role in drug discovery. Herein, a series of steroidal indole derivatives containing various substituents and steroidal skeletons were designed and synthesized with classical Fischer indole synthesis as a key step in an efficient synthetic route for the first time. The in vitro antibacterial activity of all the synthesized derivatives was evaluated against four Gram-positive strains including three Methicillin-Resistant Staphylococcus aureus. Compound 11e displayed the most potent antibacterial activity (MIC = 1-2 μg/mL) with low cytotoxicity and hemolytic activity. Derivative 11e displayed more rapid bactericidal kinetic than vancomycin in the time-kill study and was less likely to induce bacterial resistance. Moreover, the preliminary antibacterial mechanism explorations indicated that compound 11e could effectively inhibit biofilm formation, promote the accumulation of reactive oxygen species, decrease bacterial metabolism, and destroy bacterial cell membranes to exert its antibacterial effects. The study of in vivo antibacterial activity suggested that compound 11e could significantly reduce the bacteria counts in a mouse subcutaneous infection model. These findings provided a bright hope for steroidal indole derivatives as promising antibacterial candidates to settle drug resistance.

Navigating The Deuteration Landscape: Innovations, Challenges, and Clinical Potential of Deuterioindoles

Indoles, pivotal to the realm of drug discovery, underpin numerous FDA-approved therapeutics. Despite their clinical benefits, pharmacokinetic and toxicity concerns have occasionally hampered their broader application. A notable advancement in this domain is the substitution of hydrogen atoms with deuterium, known as deuterium modification, which significantly enhances the pharmacological properties of these compounds. This review elucidates the progression of deuterium chemistry, culminating in approval of Deutetrabenazine in 2017. This milestone has catalyzed additional research into deuterated indoles, such as Dosimertinib, which have demonstrated enhancements in stability, toxicity profiles, and therapeutic efficacy. Moreover, the review addresses challenges and patent issues in the synthesis of deuterated indoles and highlights their potential applications in precision medicine. In the future, deuterated indoles may positively impact therapy and contribute to advances in precision medicine through molecular engineering.

Synthetic account on indoles and their analogues as potential anti-plasmodial agents

Malaria caused by P. falciparum, has been recognized as one of the major infectious diseases causing the death of several patients as per the reports from the World Health Organization. In search of effective therapeutic agents against malaria, several research groups have started working on the design and development of novel heterocycles as anti-malarial agents. Heterocycles have been recognized as the pharmacophoric features for the different types of medicinally important activities. Among all these heterocycles, nitrogen containing aza-heterocycles should not be underestimated owing to their wide therapeutic window. Amongst the aza-heterocycles, indoles and fused indoles such as marinoquinolines, isocryptolepines and their regioisomers, manzamines, neocryptolenines, and indolones have been recognized as anti-malarial agents active against P. falciparum. The present work unleashes the synthetic attempts of anti-malarial indoles and fused indoles through cyclocondensation, Fischer-indole synthesis, etc. along with the brief discussions on structure-activity relationships, in vitro or in vivo studies for the broader interest of these medicinal chemists, working on their design and development as potential anti-malarial agents.

Nuclear Quantum Effects Have a Significant Impact on UV/Vis Absorption Spectra of Chromophores in Water

Despite the broadly acknowledged importance of solvation effects on measured UV/Vis spectra in the context of solvatochromism or chemical reactions in solution, it is still an open challenge to calculate UV/Vis spectra with predictive accuracy. This is particularly true when it comes to the impact of nuclear quantum effects on these experimental observables. In the present work, we calculate the UV/Vis absorption spectrum of indole in aqueous solution with a combination of a correlated wavefunction method for computing electronic excitation energies and enhanced path integral simulations for rigorous sampling of nuclear configurations including the quantum effects in solution. After validating our approach based on gas-phase benchmarking, we demonstrate that the lineshape of the spectrum measured in aqueous solution is quantitatively recovered, without the application of any shifting, scaling, or broadening, only after including nuclear quantum effects in addition to thermal fluctuations and solvation at ambient conditions. Our findings demonstrate that nuclear quantum effects are "visible" in UV/Vis spectra of chromophores measured in solution even at room temperature and, therefore, that they must be considered computationally to achieve predictive accuracy.

Recent report on indoles as a privileged anti-viral scaffold in drug discovery

In recent years, viral infections such as COVID-19, Zika virus, Nipah virus, Ebola, Influenza, Monkeypox, and Dengue have substantially impacted global health. These outbreaks have led to heightened global health initiatives and collaborative efforts to address and mitigate these significant threats effectively. Thus, developing antiviral treatments and research in this field has become highly important. Heterocycles, particularly indole motifs, have been a valuable resource in drug discovery, as they can be used as treatments or inspire the synthesis of new potent candidates. Indole-containing drugs, such as enfuvirtide (T-20), arbidol, and delavirdine, have demonstrated significant efficacy in treating viral diseases. This review aims to comprehensively assess the latest research and developments in novel indoles as potential scaffolds for antiviral activity. We have compiled detailed information about indoles as potential antivirals by conducting a thorough literature survey from the past ten years. The review includes discussions on synthetic protocols, inhibitory concentrations, SAR study, and computational study. This review shall identify new antiviral indoles that may help to combat new viral threats in the future.

New Insights into the Modifications and Bioactivities of Indole-3- Carboxaldehyde and its Derivatives as a Potential Scaffold for Drug Design: A Mini-Review

Indole, a ubiquitous structural motif in bioactive compounds, has played a pivotal role in drug discovery. Among indole derivatives, indole-3-carboxaldehyde (I3A) has emerged as a particularly promising scaffold for the development of therapeutic agents. This review delves into the recent advancements in the chemical modification of I3A and its derivatives, highlighting their potential applications in various therapeutic areas. I3A derivatives have demonstrated a wide range of biological activities, including anti-inflammatory, anti-leishmanial, anti-cancer, anti-bacterial, antifungal, and anti-HIV properties. The structural modifications introduced to the I3A scaffold, such as substitutions on the indole ring (alkylation/arylation/halogenation), variations in the aldehyde group via condensation (Aldol/Claisen/Knoevenagel), and molecular hybridization with other reputable bioactive compounds like coumarins, chalcones, triazoles, and thiophenes, contribute to these activities. Beyond its therapeutic potential, I3A has also found applications as a ligand for Schiff base synthesis, a polymer, and a chromophore. This review provides a comprehensive overview of the latest research on I3A and its derivatives, focusing on the key reactions, modification pathways, reaction conditions, yields, and associated therapeutic activities. By understanding these advancements, researchers can gain valuable insights into the potential applications and future directions for I3A-based drug discovery.

Transcriptomic Insights into the Molecular Mechanisms of Indole Analogues from the Periplaneta americana Extract and Their Therapeutic Effects on Ulcerative Colitis

Ulcerative colitis (UC) is an inflammatory disease of the intestinal mucosa, and its incidence is steadily increasing worldwide. As a traditional Chinese medicinal insect, Periplaneta americana has been broadly utilized in clinical practice to treat wound healing. The tryptophan (Trp), tryptamine (Try), and 1,2,3,4-tetrahydrogen-β-carboline-3-carboxylic acid (Thcc) identified from P. americana concentrated ethanol-extract liquid (PACEL) exhibit significant cell proliferation-promoting and anti-inflammatory effects in the treatment of UC, but the mechanism involved remains obscure. Here, a dextran sulfate sodium (DSS)-induced UC mouse model was used to investigate the efficacy of high/low doses of PACEL, Trp, Try, and Thcc. Transcriptome sequencing was employed to detect the gene expression in the mouse intestine. The results showed that high doses of PACEL, Trp, Try, and Thcc could significantly improve weight loss and diarrhea, notably in the PACEL and Trp groups. Transcriptome analysis indicated that statistically changed genes in four treatment groups were specifically enriched in the immune system. Of these, the integrated analysis identified six hub genes (IL1β, CCL4, CXCL5, CXCR2, LCN2, and MMP9) regulated by NF-κB, which were significantly downregulated. This study investigates the molecular mechanisms underlying the UC treatment properties of indole analogues from PACEL, potentially through the inhibition of the NF-κB signaling pathway.

Cascade Reaction of Enyne-Amides with Sulfur-Ylides for the Synthesis of Indole-Tethered 5-Oxaspiro[2.4]hept-6-ene Derivatives

An unexpected cascade reaction of enyne-amides with sulfur-ylides has been developed. This cascade reaction involves cycloisomerization, dearomatic cyclopropanation, ring-opening rearomatization, and subsequent cyclopropanation, differing from the common [2 + n] cyclization of enyne-amides. A variety of (spirocyclopropane)dihydrofuran derivatives have been efficiently and conveniently synthesized in a single vessel, exhibiting excellent diastereoselectivity and good functional group tolerance.

Bisindole Compounds-Synthesis and Medicinal Properties

The indole nucleus stands out as a pharmacophore, among other aromatic heterocyclic compounds with remarkable therapeutic properties, such as benzimidazole, pyridine, quinoline, benzothiazole, and others. Moreover, a series of recent studies refer to strategies for the synthesis of bisindole derivatives, with various medicinal properties, such as antimicrobial, antiviral, anticancer, anti-Alzheimer, anti-inflammatory, antioxidant, antidiabetic, etc. Also, a series of natural bisindole compounds are mentioned in the literature for their various biological properties and as a starting point in the synthesis of other related bisindoles. Drawing from these data, we have proposed in this review to provide an overview of the synthesis techniques and medicinal qualities of the bisindolic compounds that have been mentioned in recent literature from 2010 to 2024 as well as their numerous uses in the chemistry of materials, nanomaterials, dyes, polymers, and corrosion inhibitors.

Synthesis, DFT, Molecular Docking, and Antimicrobial Studies of New Indole-Thiosemicarbazone Ligand and Their Complexes with Fe(III), Co(II), Ni(II), Cu(II)

Indole-3-carbaldehyde based novel ligand (E)-2-((1-benzyl-1H-indol-3-yl)methylene)-N-methylhydrazine-1-carbothioamide (MBIHC) and its metal complexes [(MBIHC)2FeCl2]Cl(C1), [(MBIHC-)2Co] (C2), [(MBIHC-)2Ni] (C3), and [(MBIHC-)2Cu] (C4) have been synthesized. All synthesized compounds have been characterized by various spectroanalytical techniques. The structure of MBIHC was confirmed by single-crystal X-ray data. The geometry of metal complexes was determined by spectroscopic and computational studies. In the case of iron complex, ligand MBIHC coordinated to the metal ion in bidentate mode (via nitrogen, sulphur donor atoms) while in the case of cobalt, nickel, and copper complexes ligand act as a tridentate ligand (via nitrogen, sulphur, carbene donor atoms). In vitro, antifungal and antibacterial studies of ligand and metal complexes were assayed against C. albicans, C. glabrata, E. coli, and K. pneumoniae pathogens. In antifungal activity, complex C1 exhibited a greater inhibition zone than the other compounds for the both examined fungi C. albicans (24±0.32 mm) and C. glabrata (20±0.16 mm). However, the antifungal activities of complex C2 has shown better activity against both E. coli (25±0.24 mm) and K. pneumoniae (16±0.80 mm) pathogens than the other examined compound. Complex C2 has found even better than the benchmark drug Ampiciline in case of E. coli. Further, the DFT calculations and molecular docking studies also validate the experimental bioactivity results of examined compounds.

Indole-based COX-2 inhibitors: A decade of advances in inflammation, cancer, and Alzheimer's therapy

Cyclooxygenase-2 (COX-2), a key enzyme in the cyclooxygenase family, is pivotal in producing pro-inflammatory prostaglandins, driving chronic inflammation and related disorders. Targeting COX-2 with selective inhibitors can mitigate these conditions while avoiding the gastrointestinal and hepatotoxic/nephrotoxic side effects of traditional NSAIDs. However, the selectivity towards COX-2 inhibition has been associated with cardiovascular risks, necessitating the discovery of novel molecular scaffolds avoiding CVS side effects. This review focuses on advancements in Indole-based COX-2 inhibitors from 2013 to 2024, emphasizing their potential in treating inflammation, cancer, and Alzheimer's disease. The Indole scaffold, known for its versatility, allows for comprehensive structure-activity relationship (SAR) analysis, facilitating the development of molecules with enhanced selectivity and potency. Molecules having different substituents attached to the Indole scaffold supported by molecular modeling data, is explored in detail. This review provides an concise overview of the pharmacophore profiles of Indole-based chemotherapeutics, contributing to the development of advanced strategies for selective COX-2 inhibition and addressing the challenges and opportunities in the field.

Iron-catalyzed C-7 Selective NH2 Amination of Indoles

7-Aminoindoles are important synthetic intermediates to a broad range of bioactive molecules. Transition metal-catalyzed directed C-H amination is among the most straightforward route for their synthesis, whereas methods that could directly incorporate an NH2 group in a highly selective manner remains elusive. Moreover, there is still high demand for the development of earth-abundant metal catalysis for such attractive reactivity. We present here the first C-7 selective NH2 amination of indoles through a directed homolytic aromatic substitution (HAS) with iron-aminyl radical. The reaction exhibits broad substrate scope, tolerates variety of functional groups, and is readily scalable with catalyst loading down to 0.1 mol % and turnover number (TON) up to 4500.

Substrate-Induced Cooperative Ionic Catalysis: Difunctionalization of Indole Derivatives Employing Dimethyl Carbonate

The global urge to adopt sustainable chemistry has resulted in the development of more environmentally benign strategies (EBS) that use CO2 and CO2-derived chemicals in a step-economic manner. In this context, we investigated a dual C-H methylation and (C═O)-methoxylation of indole derivatives using dimethyl carbonate (DMC) in the presence of catalytic amounts of Cs2CO3. Mechanistic insights include DMF-assisted, DMC-induced cooperative ionic catalysis, which allows DMC to act as both a nucleophilic and an electrophilic precursor, resulting in (C═O)-methoxylation and C-H methylation of N-benzylindolyl ketones.

Design and Synthesis of Potential Multi-Target Antidepressants: Exploration of 1-(4-(7-Azaindole)-3,6-dihydropyridin-1-yl)alkyl-3-(1H-indol-3-yl)pyrrolidine-2,5-dione Derivatives with Affinity for the Serotonin Transporter

We describe the design, synthesis and structure-activity relationship of a novel series of 1-(4-(7-azaindole)-3,6-dihydropyridin-1-yl)alkyl-3-(1H-indol-3-yl)pyrrolidine-2,5-dione derivatives with combined effects on the serotonin (5-HT1A) and dopamine (D2) receptors and the serotonin (5-HT), noradrenaline (NA), and dopamine (DA) transporters as multi-target directed ligands for the treatment of depression. All of the tested compounds demonstrated good affinity for the serotonin transporter (SERT). Among them, compounds 11 and 4 emerged as the lead candidates because of their promising pharmacological profile based on in vitro studies. Compound 11 displayed a high affinity for the 5-HT1A (Ki = 128.0 nM) and D2 (Ki = 51.0 nM) receptors, and the SERT (Ki = 9.2 nM) and DAT (Ki = 288.0 nM) transporters, whereas compound 4 exhibited the most desirable binding profile to SERT/NET/DAT among the series: Ki = 47.0 nM/167.0 nM/43% inhibition at 1 µM. These results suggest that compounds 4 and 11 represent templates for the future development of multi-target antidepressant drugs.

Design, Synthesis and Biological Evaluation of C3‐Indolyl/(3‐chloro‐indolyl)‐C4‐aryl/heteroaryl‐azetidin‐2‐ones

Herein, trans‐ and cis‐azetidin‐2‐ones 3–6 were strategically synthesized, capitalizing on the bioactivity of azetidin‐2‐ones and indole pharmacophore, followed by a comprehensive characterization using a diverse array of spectroscopic techniques. The sixteen azetidin‐2‐ones were examined for antimicrobial activities against both Gram‐negative (P. aeruginosa, E. coli, A. baumannii) and Gram‐positive bacteria (S. aureus, E. faecium, B. cereus), as well as against C. albicans and C. tropicalis fungal strains. The highly potent compounds (5 a, 6 b, 6 d) demonstrated maximum inhibition against all multidrug‐resistant strains, with minimum inhibitory concentrations ranging from 0.97–3.9 μg/mL, surpassing the potency of standard ampicillin (MIC: 3.12–50 μg/mL). Moreover, 6 b and 6 d exhibited significant inhibitory effects on C. albicans (MIC: 0.97 μg/mL), comparable to fluconazole. The presence of C3‐(3‐chloro‐indolyl) scaffold, combined with diverse electronic effects at N1/C4‐centers, particularly the inclusion of thiophen‐2‐yl motif, greatly influenced the activity of target compounds. Assessment of 4 d, 4 i–k and 6 d on THLE‐2 cell lines revealed their preferential safety. Molecular docking studies revealed seven compounds with active dual targeting of DNA GyrB and PBP2a proteins, demonstrating a potent broad‐spectrum antibacterial effect. In silico ADME analysis affirms positive drug‐likeness and favorable pharmacokinetic characteristics of indole‐derived hybrids, indicating a promising potential for addressing challenges in evolving multidrug resistance.

Regio- and Enantioselective N-Heterocyclic Carbene-Catalyzed Annulation of Aminoindoles Initiated by Friedel-Crafts Alkylation

Chiral indoles annulated on the benzene ring are unique and significant in natural and medicinal compounds. However, accessing these enantioenriched molecules has often been overlooked. The present study introduces an organocatalytic protocol to access these compounds efficiently, demonstrated by substrate scope, functional group tolerance, and using only 1 mol % of a chiral conjugated acid catalyst. Additionally, the study explores regioselectivity, gram-scale reactions, and follow-up transformations, underscoring the method's potential.

Design, Synthesis, and Biological Evaluation of 1,4-Dihydropyridine-Indole as a Potential Antidiabetic Agent via GLUT4 Translocation Stimulation

In the quest for the discovery of antidiabetic compounds, a series of 27 1,4-dihydropyridine-indole derivatives were synthesized using a diversity approach. These compounds were systematically evaluated for their antidiabetic activity, starting with an in vitro assessment for GLUT4 translocation stimulation in L6-GLUT4myc myotubes, followed by in vivo antihyperglycemic activity evaluation in a streptozotocin (STZ)-induced diabetic rat model. Among the synthesized compounds, 12, 14, 15, 16, 19, 27, and 35 demonstrated significant potential to stimulate GLUT4 translocation in skeletal muscle cells. Compound 19 exhibited the highest potency and was selected for in vivo evaluation. A notable reduction of 21.6% (p < 0.01) in blood glucose levels was observed after 5 h of treatment with compound 19 in STZ-induced diabetic rats. Furthermore, pharmacokinetic studies affirmed that compound 19 was favorable to oral exposure with suitable pharmacological parameters. Overall, compound 19 emerged as a promising lead compound for further structural modification and optimization.

Newly Synthesized Indolylacetic Derivatives Reduce Tumor Necrosis Factor-Mediated Neuroinflammation and Prolong Survival in Amyotrophic Lateral Sclerosis Mice

The debilitating neurodegenerative disease known as amyotrophic lateral sclerosis (ALS) is characterized by the progressive loss of motor neurons (MNs) in the brain, spinal cord, and motor cortex. The ALS neuroinflammatory component is being characterized and includes the overexpression of mediators, such as inducible nitric oxide synthase (iNOS) and tumor necrosis factor-α (TNF-α). Currently, there are no effective treatments for ALS. Indeed, riluzole, an N-methyl-D-aspartate (NMDA) glutamate receptor blocker, and edaravone, a reactive oxygen species (ROS) scavenger, are currently the sole two medications approved for ALS treatment. However, their efficacy in extending life expectancy typically amounts to only a few months. In order to improve the medicaments for the treatment of neurodegenerative diseases, preferably ALS, novel substituted 2-methyl-3-indolylacetic derivatives (compounds II-IV) were developed by combining the essential parts of two small molecules, namely, the opioids containing a 4-piperidinyl ring with indomethacin, previously shown to be efficacious in different experimental models of neuroinflammation. The synthesized compounds were evaluated for their potential capability of slowing down neurodegeneration associated with ALS progression in preclinical models of the disease in vitro and in vivo. Notably, we produced data to demonstrate that the treatment with the newly synthesized compound III: (1) prevented the upregulation of TNF-α observed in BV-2 microglial cells exposed to the toxin lipopolysaccharides (LPS), (2) preserved SHSY-5Y cell survival exposed to β-N-methylamino-l-alanine (L-BMAA) neurotoxin, and (3) mitigated motor symptoms and improved survival rate of SOD1G93A ALS mice. In conclusion, the findings of the present work support the potential of the synthesized indolylacetic derivatives II-IV in ALS treatment. Indeed, in the attempt to realize an association between two active molecules, we assumed that the combination of the indispensable moieties of two small molecules (the opioids containing a 4-piperidinyl ring with the FANS indomethacin) might lead to new medicaments potentially useful for the treatment of amyotrophic lateral sclerosis.

Indole Compounds in Oncology: Therapeutic Potential and Mechanistic Insights

Cancer remains a formidable global health challenge, with current treatment modalities such as chemotherapy, radiotherapy, surgery, and targeted therapy often hindered by low efficacy and adverse side effects. The indole scaffold, a prominent heterocyclic structure, has emerged as a promising candidate in the fight against cancer. This review consolidates recent advancements in developing natural and synthetic indolyl analogs, highlighting their antiproliferative activities against various cancer types over the past five years. These analogs are categorized based on their efficacy against common cancer types, supported by biochemical assays demonstrating their antiproliferative properties. In this review, emphasis is placed on elucidating the mechanisms of action of these compounds. Given the limitations of conventional cancer therapies, developing targeted therapeutics with enhanced selectivity and reduced side effects remains a critical focus in oncological research.

Primary amine-catalyzed enantioselective 1,4-Michael addition reaction of pyrazolin-5-ones to α,β-unsaturated ketones

The enantioselective 1,4-addition reaction of pyrazolin-5-ones to α,β-unsaturated ketones catalyzed by a cinchona alkaloid-derived primary amine-Brønsted acid composite is reported. Both enantiomers of the anticipated pyrazole derivatives were obtained in good to excellent yields (up to 97%) and high enantioselectivities (up to 98.5% ee) under mild reaction conditions. In addition, this protocol was further expanded to synthesize highly enantioenriched hybrid molecules bearing biologically relevant heterocycles.

Selective Synthesis of 3-(1H-Tetrazol-5-yl)-indoles from 2H-Azirines and Arynes

A new selective synthetic approach to indole derivatives bearing a tetrazole moiety has been developed. Arynes, generated in situ from o-(trimethylsilyl)aryl triflates and KF, reacted smoothly with 2-(2-benzyl-2H-tetrazol-5-yl)-2H-azirines to give 3-(2-benzyl-2H-tetrazol-5-yl)-indole derivatives with high selectivity. Deprotection of the tetrazole moiety gave 3-(1H-tetrazol-5-yl)-indole derivatives.

Identifying Potential SOS1 Inhibitors via Virtual Screening of Multiple Small Molecule Libraries against KRAS-SOS1 Interaction

The RAS-MAPK signaling pathway, crucial for cell proliferation and differentiation, involves key proteins KRAS and SOS1. Mutations in the KRAS and SOS1 genes are implicated in various cancer types, including pancreatic, lung, and juvenile myelomonocytic leukemia. There is considerable interest in identifying inhibitors targeting KRAS and SOS1 to explore potential therapeutic strategies for cancer treatment. In this study, advanced in silico techniques were employed to screen small molecule libraries at this interface, leading to the identification of promising lead compounds as potential SOS1 inhibitors. Comparative analysis of the average binding free energies of these predicted potent compounds with known SOS1 small molecule inhibitors revealed that the identified compounds display similar or even superior predicted binding affinities compared to the known inhibitors. These findings offer valuable insights into the potential of these compounds as candidates for further development as effective anti-cancer agents.

Mechanochemical C-H Arylation and Alkylation of Indoles Using 3 d Transition Metal and Zero-Valent Magnesium

Although the 3 d transition-metal catalyzed C-H functionalization have been extensively employed to promote the formation of valuable carbon-carbon bonds, the persistent problems, including the use of sensitive Grignard reagents and the rigorous operations (solvent-drying, inert gas protection, metal pre-activation and RMgX addition rate control), still leave great room for further development of sustainable methodologies. Herein, we report a mechanochemical technology toward in-situ preparation of highly sensitive organomagnesium reagents, and thus building two general 3 d transition-metal catalytic platforms that enables regioselective arylation and alkylation of indoles with a wide variety of halides (including those containing post transformable functionalities and heteroaromatic rings). This mechanochemical strategy also brings unique reactivity and high step-economy in producing functionalized N-free indole products.

Indole-Based Compounds in the Development of Anti-Neurodegenerative Agents

Neurodegeneration is a gradual decay process leading to the depletion of neurons in both the central and peripheral nervous systems, ultimately resulting in cognitive dysfunctions and the deterioration of brain functions, alongside a decline in motor skills and behavioral capabilities. Neurodegenerative disorders (NDs) impose a substantial socio-economic strain on society, aggravated by the advancing age of the world population and the absence of effective remedies, predicting a negative future. In this context, the urgency of discovering viable therapies is critical and, despite significant efforts by medicinal chemists in developing potential drug candidates and exploring various small molecules as therapeutics, regrettably, a truly effective treatment is yet to be found. Nitrogen heterocyclic compounds, and particularly those containing the indole nucleus, which has emerged as privileged scaffold, have attracted particular attention for a variety of pharmacological applications. This review analyzes the rational design strategy adopted by different research groups for the development of anti-neurodegenerative indole-based compounds which have the potential to modulate various molecular targets involved in NDs, with reference to the most recent advances between 2018 and 2023.

Development in the Synthesis of Bioactive Thiazole-Based Heterocyclic Hybrids Utilizing Phenacyl Bromide

Heterocyclic hybrid frameworks represent a burgeoning domain within the realms of drug discovery and medicinal chemistry, attracting considerable attention in recent years. Thiazole pharmacophore fragments, inherent in natural products such as peptide alkaloids, metabolites, and cyclopeptides, have demonstrated a broad spectrum of pharmacological potentials. Given their profound biological significance, a plethora of thiazole-based hybrids have been synthesized through the conjugation of thiazole moieties with bioactive pyrazole and pyrazoline fragments. This review systematically presents a compendium of robust methodologies for the synthesis of thiazole-linked hybrids, employing the (3 + 2) heterocyclization reaction, specifically the Hantzsch-thiazole synthesis, utilizing phenacyl bromide as the substrate. The strategic approach of molecular hybridization has markedly enhanced drug efficacy, mitigated resistance to multiple drugs, and minimized toxicity concerns. The resultant thiazole-linked hybrids exhibit a myriad of medicinal properties viz. anticancer, antibacterial, anticonvulsant, antifungal, antiviral, and antioxidant activities. This compilation of methodologies and insights serves as a valuable resource for medicinal chemists and researchers engaged in the design of novel thiazole-linked hybrids endowed with therapeutic attribute.

Discovery of indolylacryloyl-derived oxacins as novel potential broad-spectrum antibacterial candidates

The emergence of serious bacterial resistance towards clinical oxacins poses a considerable threat to global public health, necessitating the development of novel structural antibacterial agents. Seven types of novel indolylacryloyl-derived oxacins (IDOs) were designed and synthesized for the first time from commercial 3,4-difluoroaniline via an eight-step procedure. The synthesized compounds were characterized by modern spectroscopic techniques. All target molecules were evaluated for antimicrobial activities. Most of the prepared IDOs showed a broad antibacterial spectrum and strong activities against the tested strains, especially ethoxycarbonyl IDO 10d (0.25-0.5 μg/mL) and hydroxyethyl IDO 10e (0.25-1 μg/mL) exhibited much superior antibacterial efficacies to reference drug norfloxacin. These highly active IDOs also displayed low hemolysis, cytotoxicity and resistance, as well as rapid bactericidal capacity. Further investigations indicated that ethoxycarbonyl IDO 10d and hydroxyethyl IDO 10e could effectively reduce the exopolysaccharide content and eradicate the formed biofilm, which might delay the development of drug resistance. Preliminary exploration of the antibacterial mechanism revealed that active IDOs could not only destroy membrane integrity, resulting in changes in membrane permeability, but also promote the accumulation of reactive oxygen species, leading to the production of malondialdehyde and decreased bacterial metabolism. Moreover, they exhibited the capability to bind with DNA and DNA gyrase, forming supramolecular complexes through various noncovalent interactions, thereby inhibiting DNA replication and causing bacterial death. All the above results suggested that the newly developed indolylacryloyl-derived oxacins should hold great promise as potential multitargeting broad-spectrum antibacterial candidates to overcome drug resistance.

Deciphering psilocybin: Cytotoxicity, anti-inflammatory effects, and mechanistic insights

A decade of clinical research has indicated psilocybin's effectiveness in treating various neuropsychiatric disorders, such as depression and substance abuse. The correlation between increased pro-inflammatory cytokines and the severity of neuropsychiatric symptoms, along with the known anti-inflammatory potential of some psychedelics, suggests an immunomodulatory role for psilocybin. This study aims to understand the mechanism of action of psilocybin by investigating the cytotoxic and immunomodulatory effects of psilocybin and psilocin on both resting and LPS-activated RAW 264.7 murine macrophages. The study evaluated the cytotoxicity of psilocybin and psilocin using an LDH assay across various doses and assessed their impact on cytokine production in RAW 264.7 cells, measuring cytokine expression via ELISA. Different doses, including those above and below the LC50, were used in both pre-treatment and post-treatment approaches. The LDH assay revealed that psilocybin is almost twice as cytotoxic as psilocin, with an LC50 of 12 ng/ml and 28 ng/ml, respectively. In resting macrophages, both psilocybin and psilocin triggered significant release of TNF- α after 4 h, with the lowest doses inducing higher levels of the cytokine than the highest doses. IL-10 expression in resting cells was only triggered by the highest dose of psilocin in the 4-hour incubation group. In LPS-stimulated cells, psilocin reduced TNF- α levels more than psilocybin in pre-treatment and post-treatment, with no significant effects on IL-10 in pre-treatment. Psilocin, but not psilocybin, induced a significant increase of IL-10 in post-treatment, leading to the conclusion that psilocin, but not psilocybin, exerts anti-inflammatory effects on classically activated macrophages.

Transition-Metal-Free Synthesis of 2-Substituted Benzo[cd]Indoles via the Reaction of 1-Halo-8-lithionaphthalenes with Nitriles

A simple and effective organolithium approach to the synthesis of 2-substituted benzo[cd]indoles from peri-dihalonaphthalenes and nitriles has been developed. The reaction proceeds via a surprisingly easy intramolecular aromatic nucleophilic substitution facilitated by the "clothespin effect". The discovered transformation provides good isolated yields, allows usage of an extensive range of nitriles, and demonstrates a good substituents tolerance. UV-absorption and NMR spectra of the obtained benzo[cd]indoles and their protonated forms demonstrated exclusive protonation to the indole nitrogen atom even in the presence of two NMe2 groups in positions 5 and 6 (i. e. "proton sponge" moiety).

Discovery of Novel Compounds for Combating Rising Severity of Plant Diseases Caused by Fungi and Viruses

In recent years, the severity of plant diseases caused by plant pathogenic fungi and viruses has been on the rise. However, there is a limited availability of pesticide chemicals in the market for effectively controlling both fungal and viral infections. To solve this problem, a series of novel pyrimidine derivatives containing a 1,3,4-oxadiazole thioether fragment were synthesized. Among them, compound 6s exhibited remarkable in vivo protection activity against tobacco mosaic virus, demonstrating the superior 50% effective concentration (EC50) value of 0.42 μM, outperforming ningnanmycin (0.60 μM). Meanwhile, compound 6s exhibited remarkable antifungal activity against Botrytis cinerea Pers. in postharvest blueberry in vitro, with an EC50 value of 0.011 μM, surpassing the inhibition rate of Pyrimethanil (0.262 μM). Additionally, compound 6s also demonstrated remarkable curative and protection activities against blueberry fruit gray mold in vivo, with control efficiencies of 54.2 and 60.4% at 200 μg/mL concentration, respectively, which were comparable to those of Pyrimethanil (49.3 and 63.9%, respectively). Scanning electron microscopy showed that the compound 6s-treated hyphae of B. cinerea Pers. in postharvest blueberry became abnormally collapsed and shriveled. Furthermore, the molecular docking simulation demonstrated that compound 6s formed hydrogen bonds with SER-17, ARG-43, and SER-39 of succinate dehydrogenase (SDH), providing a possible explanation for the mechanism of action between the target compounds and SDH. This study represents the first report on the antiviral and antifungal activities of novel pyrimidine derivatives containing a 1,3,4-oxadiazole thioether fragment.

Study of nitrogen heterocycles as DNA/HSA binder, topoisomerase inhibitors and toxicological safety

Four new nitrogen-containing heterocyclic derivatives (acridine, quinoline, indole, pyridine) were synthesized and their biological properties were evaluated. The compounds showed affinity for DNA and HSA, with CAIC and CAAC displaying higher binding constants (Kb) of 9.54 × 104 and 1.06 × 106, respectively. The fluorescence quenching assay (Ksv) revealed suppression values ranging from 0.34 to 0.64 × 103 M-1 for ethidium bromide (EB) and 0.1 to 0.34 × 103 M-1 for acridine orange (AO). Molecular docking confirmed the competition of the derivatives with intercalation probes at the same binding site. At 10 μM concentrations, the derivatives inhibited topoisomerase IIα activity. In the antiproliferative assays, the compounds demonstrated activity against MCF-7 and T47-D tumor cells and nonhemolytic profile. Regarding toxicity, no acute effects were observed in the embryos. However, some compounds caused enzymatic and cardiac changes, particularly the CAIC, which increased SOD activity and altered heart rate compared to the control. These findings suggest potential antitumor action of the derivatives and indicate that substituting the acridine core with different cores does not interfere with their interaction and topoisomerase inhibition. Further investigations are required to assess possible toxicological effects, including reactive oxygen species generation.

Thiazole-based analogues as potential antibacterial agents against methicillin-resistant Staphylococcus aureus (MRSA) and their SAR elucidation

In recent years, the overuse of antibiotics has resulted in the emergence of antibiotic resistance, which is a serious global health problem. Methicillin-resistant Staphylococcus aureus (MRSA) is a common and virulent bacterium in clinical practice. Numerous researchers have focused on developing new candidate drugs that are effective, less toxic, and can overcome MRSA resistance. Thiazole derivatives have been found to exhibit antibacterial activity against drug-sensitive and drug-resistant pathogens. By hybridizing thiazole with other antibacterial pharmacophores, it is possible to obtain more effective antibacterial candidate drugs. Thiazole derivatives have shown potential in developing new drugs that can overcome drug resistance, reduce toxicity, and improve pharmacokinetic characteristics. This article reviews the recent progress of thiazole compounds as potential antibacterial compounds and examines the structure-activity relationship (SAR) in various directions. It covers articles published from 2018 to 2023, providing a comprehensive platform to plan and develop new thiazole-based small MRSA growth inhibitors with minimal side effects.

N-Indolyl diiron vinyliminium complexes exhibit antiproliferative effects in cancer cells associated with disruption of mitochondrial homeostasis, ROS scavenging, and antioxidant activity

The indole scaffold has been established as a key organic moiety for developing new drugs; on the other hand, a range of diiron bis-cyclopentadienyl complexes have recently emerged for their promising anticancer potential. Here, we report the synthesis of novel diiron complexes with an indole-functionalized vinyliminium ligand (2-5) and an indole-lacking analogue for comparative purposes (6), which were characterized by analytical and spectroscopic techniques. Complexes 2-6 are substantially stable in DMSO‑d6 and DMEM-d solutions at 37 °C (8% average degradation after 48 h) and display a balanced hydrophilic/lipophilic behaviour (LogPow values in the range -0.32 to 0.47), associated with appreciable water solubility. The complexes display selective antiproliferative potency towards several cancer cells in monolayer cultures, mainly in the low micromolar range, with reduced toxicity towards noncancerous epithelial cells. Thus, the cytotoxicity of the complexes is comparable to or better than clinically used metallopharmaceutical cisplatin. Comparing the antiproliferative activity obtained for complexes containing different ligands, we confirmed the importance of the indolyl group in the mechanism of antiproliferative activity of these complexes. Cell-based mechanistic studies suggest that the investigated diiron vinyliminium complexes (DVCs) show cytostatic rather than cytotoxic effects and subsequently induce a population of cells to undergo apoptosis. Furthermore, the molecular mechanism of action involves interactions with mitochondrial DNA and proteins, the reactive oxygen species (ROS)-scavenging properties and antioxidant activity of these complexes in cancer cells. This study highlights the importance of DVCs to their cancer cell activity and reinforces their prospective therapeutic potential as anticancer agents.

Amphiphilic small molecule antimicrobials: From cationic antimicrobial peptides (CAMPs) to mechanism-related, structurally-diverse antimicrobials

Bacterial infections are characterized by their rapid and widespread proliferation, leading to significant morbidity. Despite the availability of a variety of antimicrobial drugs, the resistance exhibited by pathogenic microorganisms towards these drugs demonstrates a consistent upward trajectory year after year. This trend can be attributed to the abuse or misuse of antibiotics. Although antimicrobial peptides can avoid the emergence of drug resistance to a certain extent, their clinical application has been hindered by factors such as their high production cost, poor in vivo stability, and potential cytotoxicity. Consequently, there arises an urgent need for the development of novel antimicrobial drugs. Small-molecule amphiphatic antimicrobials have a good prospect for research and development. These peptides hold the potential to address several issues, including the high cost of antimicrobial peptide production, poor in vivo stability, and cytotoxicity. Moreover, they exhibit the capability to overcome bacterial resistance, thereby considerably satisfying market demands and clinical needs. This paper reviews recent research pertaining to small molecule host-defending amphiphatic antimicrobials with cationic amphiphilic structures. It focuses on the design concepts, inherent relationships, drug-like properties, antimicrobial activities, application prospects, and emerging screening methods for novel antimicrobial. This review assumes paramount importance in mitigating the current shortcomings of antimicrobial agents. It also provides potential new ideas and methodologies for the research and development of antimicrobial agents.

Azo Coupling of Indoles Revisited: Synthesis of Biindolyl Photoswitches via the Azo-Coupling/C-H Functionalization Domino Approach

When azo coupling of aryldiazonium salts with indoles was carried out in aprotic nonpolar solvent on air, a pseudo-three-component reaction has been discovered. Azo coupling is followed by a nucleophilic addition of a second indole unit to the indolium intermediate; aromatization and oxidation are achieved under air.

Consecutive four-component synthesis of trisubstituted 3-iodoindoles by an alkynylation-cyclization-iodination-alkylation sequence

A library of 19 differently substituted 3-iodoindoles is generated by a consecutive four-component reaction starting from ortho-haloanilines, terminal alkynes, N-iodosuccinimide, and alkyl halides in yields of 11-69%. Initiated by a copper-free alkynylation, followed by a base-catalyzed cyclizive indole formation, electrophilic iodination, and finally electrophilic trapping of the intermediary indole anion with alkyl halides provides a concise one-pot synthesis of 3-iodoindoles. The latter are valuable substrates for Suzuki arylations, which are exemplified with the syntheses of four derivatives, some of them are blue emitters in solution and in the solid state, in good yield.

Biomedical applications of selective metal complexes of indole, benzimidazole, benzothiazole and benzoxazole: A review (From 2015 to 2022)

Indole, benzoxazole benzothiazole and benzimidazole are excellent classes of organic heterocyclic compounds. These compounds show significant application in pharmacy, industries, dyes, medicine, polymers and food packages. These compounds also form metal complexes with copper, zinc, cadmium, nickel, cobalt, platinum, gold, palladium chromium, silver, iron, and other metals that have shown to be significant applications. Recently, researchers have attracted enormous attention toward heterocyclic compounds such as indole, benzimidazole, benzothiazole, benzoxazole, and their complexes due to their excellent medicinal applications such as anti-ulcerogenic, anti-cancer, antihypertensive, antifungal, anti-inflammatory, antitubercular, antiparasitic, anti-obesity, antimalarial, antiglycation, antiviral potency, antineuropathic, analgesic antioxidant, antihistaminic, and antibacterial potentials. In this article, we summarize the medicinal applications of these compounds as well as their metal complexes. We hope this article will help researchers in designing and synthesizing novel and potent compounds with significant applications in various fields.

Facile Access to Structurally Diverse Antimalarial Indoles Using a One-Pot A3 Coupling and Domino Cyclization Approach

A multistep and diversity-oriented synthetic route aiming at the A3 coupling/domino cyclization of o-ethynyl anilines, aldehydes and s-amines is described. The preparation of the corresponding precursors included a series of transformations, such as haloperoxidation and Sonogashira cross-coupling reactions, amine protection, desilylation and amine reduction. Some products of the multicomponent reaction underwent further detosylation and Suzuki coupling. The resulting library of structurally diverse compounds was evaluated against blood and liver stage malaria parasites, which revealed a promising lead with sub-micromolar activity against intra-erythrocytic forms of Plasmodium falciparum. The results from this hit-to-lead optimization are hereby reported for the first time.

Design, Synthesis, ADME, and Anticancer Studies of Newer N-Aryl-5-(3,4,5-Trifluorophenyl)-1,3,4-Oxadiazol-2-Amines: An Insight into Experimental and Theoretical Investigations

In continuance of our investigation into the anticancer activity of oxadiazoles, we report here the preparation of 10 new 1,3,4-oxadiazole analogues using the scaffold hopping technique. We have prepared the oxadiazoles having a common pharmacophoric structure (oxadiazole linked aryl nucleus) as seen in the reported anticancer agents IMC-038525 (tubulin inhibitor), IMC-094332 (tubulin inhibitor), and FATB (isosteric replacement of the S of thiadiazole with the O of oxadiazole). All of the oxadiazole analogues were predicted for their absorption, distribution, metabolism, and excretion (ADME) profiles and toxicity studies. All of the compounds were found to follow Lipinski's rule of 5 with a safe toxicity profile (Class IV compound) against immunotoxicity, mutagenicity, and toxicity. All of the compounds were synthesized and characterized using spectral data, followed by their anticancer activity tested in a single-dose assay at 10 μM as reported by the National Cancer Institute (NCI US) Protocol against nearly 59 cancer cell lines obtained from nine panels, including non-small-cell lung, ovarian, breast, central nervous system (CNS), colon, leukemia, prostate, and cancer melanoma. N-(2,4-Dimethylphenyl)-5-(3,4,5-trifluorophenyl)-1,3,4-oxadiazol-2-amine (6h) displayed significant anticancer activity against SNB-19, OVCAR-8, and NCI-H40 with percent growth inhibitions (PGIs) of 86.61, 85.26, and 75.99 and moderate anticancer activity against HOP-92, SNB-75, ACHN, NCI/ADR-RES, 786-O, A549/ATCC, HCT-116, MDA-MB-231, and SF-295 with PGIs of 67.55, 65.46, 59.09, 59.02, 57.88, 56.88, 56.53, 56.4, and 51.88, respectively. The compound 6h also registered better anticancer activity than Imatinib against CNS, ovarian, renal, breast, prostate, and melanoma cancers with average PGIs of 56.18, 40.41, 36.36, 27.61, 22.61, and 10.33, respectively. Molecular docking against tubulin, one of the appealing cancer targets, demonstrated an efficient binding within the binding site of combretastatin A4. The ligand 6h (docking score = -8.144 kcal/mol) interacted π-cationically with the residue Lys352 (with the oxadiazole ring). Furthermore, molecular dynamic (MD) simulation studies in complex with the tubulin-combretastatin A4 protein and ligand 6h were performed to examine the dynamic stability and conformational behavior.

On the Barton Copper-Catalyzed C3-Arylation of Indoles using Triarylbismuth bis(trifluoroacetate) Reagents

We disclose herein our detailed investigation into the Barton copper-promoted C3-arylation of indoles using triarylbismuth bis(trifluoroacetates). The arylation of unsubstituted 1H-indole using Barton's conditions gave a low yield of the C3-arylated indole, along with small amounts of the product of double C2/C3-arylation and traces of the product of C2 arylation. On the contrary, the arylation of indoles blocked at the C2 position is highly efficient, affording the desired products of C3-arylation in good to excellent yields. The reaction operates under simple conditions, shows good substrate scope, excellent functional group compatibility, and allows the transfer of electron-neutral or deficient aryl groups. Computational studies propose a mechanism involving a trifluoroacetate-assisted C-H activation step.