Synthesis and anticancer activity of 2,4-disubstituted furo[3,2-b]indole derivatives

Controllable Synthesis of Benzo[b]furo[2,3-d]azepines or Furo[3,2-b]indoles via Intermolecular Oxidative Annulation of 2-(Furan-2-yl)anilines and Propargyl Carbonates versus Intramolecular C-H Amination Reactions

Two novel Pd-catalyzed protocols for the controllable synthesis of benzo[b]furo[2,3-d]azepines and furo[3,2-b]indoles have been developed by intermolecular oxidative annulation of 2-(furan-2-yl)anilines and propargyl carbonates versus intramolecular C-H amination reactions. These two protocols feature great scalability, functional group tolerance, and relatively mild reaction conditions. Notably, the robust methodologies could also provide valuable opportunities for assembling azepine-fused benzothiophene, indole-fused benzothiophene, and indole-fused benzimidazole, which may have potential applications in the synthesis of related pharmaceuticals or polymeric materials.

Indoles as promising Therapeutics: A review of recent drug discovery efforts

Indole, a fundamental heterocyclic core, has emerged as a cornerstone in the medicinal chemistry due to its diverse biological activities and structural versatility. This aromatic compound, present in natural as well as synthetic compounds, offers a versatile platform for the drug discovery. By strategically incorporating functional groups or pharmacophores, researchers can tailor indole-derivatives to target a wide range of diseases. This review delves into the multifaceted applications of indole derivatives, highlighting their potential as therapeutic agents for cancer, diabetes, depression, Alzheimer's diseases, Parkinson's disease, etc. emphasizing how indole derivatives can enhance potency and selectivity. By understanding the structure-activity relationship of indole compounds, scientists can develop innovative drug candidates with improved therapeutic profiles. The review highlights the diverse nature of indole-based derivatives along with the structure-activity relationshipThe current review comprehensively covers the advancements and developments in the field over the past seven years, specifically from 2017 to 2024. This timeframe was selected to provide an up-to-date and thorough analysis of recent progress, capturing significant trends, breakthroughs, and emerging insights within the domain. By focusing on this period, the review ensures relevance and highlights the evolving landscape of research, offering a detailed synthesis of key findings and their implications for future studies.

Nitrogen-fused Heterocycles: Empowering Anticancer Drug Discovery

The worldwide impact of cancer is further compounded by the constraints of current anticancer medications, which frequently exhibit a lack of selectivity, raise safety apprehensions, result in significant adverse reactions, and encounter resistance mechanisms. The current situation highlights the pressing need to develop novel and more precise anticancer agents that prioritize safety and target specificity. Remarkably, more than 85% of drugs with physiological activity contain heterocyclic structures or at least one heteroatom. Nitrogen-containing heterocycles hold a significant position among these compounds, emerging as the most prevalent framework within the realm of heterocyclic chemistry. This article explores the medicinal chemistry behind these molecules, highlighting their potential as game-changing possibilities for anticancer medication development. The analysis highlights the inherent structural variety in nitrogen-containing heterocycles, revealing their potential to be customized for creating personalized anticancer medications. It also emphasizes the importance of computational techniques and studies on the relationships between structure and activity, providing a road map for rational medication design and optimization. Nitrogen- containing heterocycles are a promising new area of study in the fight against cancer, and this review summarises the state of the field so far. By utilizing their inherent characteristics and exploiting cooperative scientific investigations, these heterocyclic substances exhibit potential at the forefront of pioneering therapeutic approaches in combating the multifaceted obstacles posed by cancer.

Advances in antitumor research of HIF-1α inhibitor YC-1 and its derivatives

Generally, hypoxia-inducible factor-1α (HIF-1α) is highly expressed in solid tumors, it plays a key role in the occurrence and development of tumors, hindering cancer treatment in various ways. The antitumor activity and pharmacological mechanism of YC-1 [3-(5'-hydroxymethyl-2'-furyl)-1‑benzyl indazole], an HIF-1α inhibitor, and the design and synthesis of its derivatives have attracted tremendous attention in the field of antitumor research. YC-1 is a potential drug candidate and a lead compound for tumor therapy. Hence, the multifaceted mechanism of action of YC-1 and the structure activity relationship (SAR) of its derivatives are important factors to be considered for the development of HIF-1α inhibitors. Therefore, this review aimed to provide a comprehensive overview of the various antitumor mechanisms of YC-1 in antitumor research and an in-depth summary of the SAR for the development of its derivatives. A full understanding and discussion of these aspects are expected to provide potential ideas for developing novel HIF-1α inhibitors and antitumor drugs belonging to the YC-1 class. The review also highlighted the application prospects of the YC-1 class of potential antitumor candidates, and provided some unique insights about these antitumor agents.

Atroposelective Construction of Nine-Membered Carbonate-Bridged Biaryls

We herein demonstrated an efficient method for the atroposelective construction of nine-membered carbonate-bridged biaryls through vinylidene ortho-quinone methide (VQM) intermediates. Diverse products with desirable pharmacological features were synthesized in satisfying yields and good to excellent enantioselectivities. In subsequent bioassays, several agents showed considerable antiproliferative activity via the mitochondrial-related apoptosis mechanism. Further transformations produced more structural diversity and may inspire new ideas for developing functional molecules.

Chemistry of 2-Vinylindoles: Synthesis and Applications

As a class of compounds, 2-vinylindoles have demonstrated a wide range of biological properties. Due to the general interest in these synthons, new divergent protocols of chemical synthesis have been...

TFA-catalyzed Q-Tube Reactor-Assisted Strategy for the Synthesis of Pyrido[1,2-b][1,2,4]triazine and Pyrido[1',2':2,3][1,2,4]triazino[5,6-b]indole Derivatives

An efficient high-pressure-assisted trifluoroacetic acid-catalyzed protocol for synthesizing unreported novel pyrido[1,2-b][1,2,4]triazine and pyrido[1',2':2,3][1,2,4]triazino[5,6-b]indole derivatives has been established. This strategy includes the condensation reactions of various 1-amino-2-imino-4-arylpyridine-3-carbonitrile derivatives with indoline-2,3-dione (isatin) derivatives and α-keto acids such as pyruvic acid and phenylglyoxylic acid. This strategy includes utilizing the Q-tube reactor as an efficient and safe tool to conduct these reactions under high-pressure conditions. In addition, trifluoroacetic acid was used to induce this transformation. In this research, conducting the targeted reactions under high pressure using the Q-tube reactor was found to be superb in comparison to that under the traditional refluxing conditions. X-ray single-crystal analysis was utilized in this study to authenticate the structure of the synthesized products.

Dibrominative Spirocyclization of 2-Butynolyl Anilides: Synthesis of gem-Dibromospirocyclic Benzo[d][1,3]oxazines and Their Application in the Synthesis of 4H-Furo[3,2-b]indoles

The combination of catalytic aqueous hydrochloric acid (HCl) and N-bromosuccinimide (NBS) generated electrophilic bromine monochloride (BrCl), which readily induced spiroannulation of 2-alkynolyl anilides (n = 1-3) to form gem-dibromospirocyclic benzo[d][1,3]oxazines in up to 92% yield. The reaction occurred under mild and metal-free conditions using EtOAc as a green solvent. The resulted spirocyclic products contained benzo[d][1,3]oxazine, which was useful both as a pharmacophore and synthetic precursor. In addition, the current protocol allowed to effortlessly introduce the sp³-gem-dibromide carbon adjacent to the sterically demanding spiroketal center. These spiroheterocycles (n = 1) were shown to be synthetically versatile and conveniently maneuvered. Base-promoted debrominative aromatization of these spirocycles unmasked rare and synthetically useful 2-aryl-3-bromofurans in mostly excellent yields. These 3-bromofurans were well-suited substrates for intramolecular Ullmann C-N bond coupling to construct difficult-to-prepare 4H-furo[3,2-b]indoles. Additionally, the current protocol was flexible and adaptable to preparing the gem-dichloride variants.

A brief review of the biological potential of indole derivatives

Background

Various bioactive aromatic compounds containing the indole nucleus showed clinical and biological applications. Indole scaffold has been found in many of the important synthetic drug molecules which gave a valuable idea for treatment and binds with high affinity to the multiple receptors helpful in developing new useful derivatives.

Main text

Indole derivatives possess various biological activities, i.e., antiviral, anti-inflammatory, anticancer, anti-HIV, antioxidant, antimicrobial, antitubercular, antidiabetic, antimalarial, anticholinesterase activities, etc. which created interest among researchers to synthesize a variety of indole derivatives.

Conclusion

From the literature, it is revealed that indole derivatives have diverse biological activities and also have an immeasurable potential to be explored for newer therapeutic possibilities.

Enantioselective Dehydrative γ-Arylation of α-Indolyl Propargylic Alcohols with Phenols: Access to Chiral Tetrasubstituted Allenes and Naphthopyrans

Herein, we report an enantioselective dehydrative γ-arylation of α-indolyl propargylic alcohols with phenols via organocatalysis, which provides efficient access to chiral tetrasubstituted allenes and naphthopyrans in high yields with excellent regio- and enantioselectivities under mild conditions. This method features the use of cheaply available naphthols/phenols as the C-H aryl source and liberating water as the sole byproduct. Control experiments suggest that the excellent enantioselectivity and remote regioselectivity stem from dual hydrogen-bonding interaction with the chiral phosphoric acid catalyst.

Synthesis of Indolyl Pyrazole Scaffolds as Potential Anti-cancer Agents and their Molecular Modelling Studies

Background::

Indole and pyrazoles are one of the prime structural units in the field of medicinal chemistry and have been reported to exhibit a variety of biological activities specifically anti-cancer. In view of their medicinal significance, we synthesized a conjugate of the two moieties to get access to newer and potential anti-cancer agents.

Methods:

Indolyl pyrazoles [3-(1,3-diphenyl-1H-pyrazol-4-yl)-2-(1-methyl-1H-indole-3-carbon yl)acrylonitriles] (4a-l) were synthesized by adopting simple and greener protocol and all the synthesized derivatives were docked against Bcl-2 protein and the selected chemical moieties were screened for their cytotoxicity by using the MTT assay.

Results: :

All the synthesized compounds were docked against BCL-2 protein in order to understand their binding pattern. Among the 12 compounds docked, 4d, 4f, 4h, 4j, and 4l compounds exhibited better protein binding interactions and the same were screened for their anti-cancer activity against A549 (lung) cancer cell lines at a concentration of 100 μM using Doxorubicin as standard. Substitutions such as N-benzyl, N-ethyl groups and halogen groups such as Br, Cl on indole ring showed moderate activity against A-549 cell lines.

Conclusion::

Among the 5 indolyl pyrazole derivatives screened, compounds 4h and 4j showed significantly better activity with an IC50 of 33.12 and 34.24 μM, respectively. Further, structural tweaking of the synthesized new chemical entities may lead to potential hit/lead-like molecules.

Palladium-catalyzed synthesis and nucleotide pyrophosphatase inhibition of benzo[4,5]furo[3,2-b]indoles

A two-step palladium-catalyzed procedure based on Suzuki–Miyaura cross coupling, followed by a double Buchwald–Hartwig reaction, allows for the synthesis of pharmaceutically relevant benzo[4,5]furo[3,2-b]indoles in moderate to very good yield. The synthesized compounds have been analyzed with regard to their inhibitory activity (IC₅₀) of nucleotide pyrophosphatases h-NPP1 and h-NPP3. The activity lies in the nanomolar range. The results were rationalized based on docking studies.

Synthesis and characterisation of novel 4,6-dimethoxyindole-7- and -2-thiosemicarbazone derivatives: Biological evaluation as antioxidant and anticholinesterase candidates

Two sets of novel indole-based thiosemicarbazone systems 8a–d and 9a–d are prepared by the Schiff base condensation reaction of indole carbaldehydes 4 and 6 with a range of thiosemicarbazides 7a–d in high yields and purity. The antioxidant properties of the synthesised compounds 8a–d and 9a–d are determined by employing three different assays, namely 2,2-diphenyl-1-picrylhydrazyl hydrate–free radical scavenging, ABTS [2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)] cationic radical decolarization and cupric ion reducing antioxidant capacity. The anticholinesterase properties of the products are investigated by acetylcholinesterase and butyrylcholinesterase enzyme inhibition assays. The methyl-substituted compounds 8b and 9b display the highest inhibition for the ABTS assay and absorbance values for the cupric ion reducing antioxidant capacity assay, while compound 9c shows the best activity for 2,2-diphenyl-1-picrylhydrazyl hydrate assay. Moderate inhibition of acetylcholinesterase and butyrylcholinesterase is determined in the case of compound 8b.

Gold-Catalyzed Cascade Reactions of 4 H-Furo[3,2- b]indoles with Allenamides: Synthesis of Indolin-3-one Derivatives

Merging the ability of cationic gold(I) catalysts to activate unsaturated π-systems with the electrophiles-driven ring-opening reactions of furans, we describe a new approach to synthesize 2-spiroindolin-3-ones from 4 H-furo[3,2- b]indoles. The reaction occurs through a cascade sequence involving addition of a gold-activated allene to the furan moiety of the starting furoindole followed by a ring-opening/ring-closing event affording 2-spirocyclopentane-1,2-dihydro-3 H-indolin-3-ones in moderate to good yields.

Synthesis of furo[3,2-b:4,5-b']diindoles and their optical and electrochemical properties

An efficient two-step palladium catalyzed synthesis of furo[3,2-b:4,5-b']diindoles, a hitherto unknown symmetrical heterocyclic core structure, was developed. The synthesis is based on a regioselective Suzuki-Miyaura cross coupling reaction of tetrabromofuran and subsequent double N-arylation. Selected compounds were studied with regard to their optical and electrochemical properties. The compounds show fluorescence with high quantum yields and non-reversible oxidation events. The compounds possess similar HOMO-LUMO band gaps compared to their sulfur and nitrogen analogs. Variation of the substituents hardly affects the HOMO-LUMO gap, but allows for some fine-tuning of the electron affinity and ionization potential as well as quantum yields. The compounds prepared represent interesting candidates for the development of organic electronic materials.

Rational modification of semaxanib and sunitinib for developing a tumor growth inhibitor targeting ATP binding site of tyrosine kinase

Analysis of the crystal structure of tyrosine kinase in complexation with an ATP analogue, supplemented with the molecular docking studies of semaxanib and sunitinib in the ATP binding site of the enzyme enabled us to make design of a series of tyrosine kinase inhibitors. The combination of pyrrole and indolinone in one molecule and placement of appropriate substituent thereof made the molecule compatible for the hydrophobic sub-pocket of the enzyme. Screening of the compounds over 60 cell line panel of human tumor cell lines identified compound 3a that exhibited GI₅₀ 35 nM and 63 nM against MCF7 and MDA-MB-468 cell lines of breast cancer.

N'-((2-(6-bromo-2-oxo-2H-chromen-3-yl)-1H-indol-3-yl)methylene)benzohydrazide as a probable Bcl-2/Bcl-xL inhibitor with apoptotic and anti-metastatic potential

A wide number of marketed drugs and drug candidates in cancer clinical development contain halogen substituents. The aim of the present study was to synthesize a series of halogen incorporated indole-coumarin hybrid schiff bases - N'-((2-(2-oxo-2H-chromen-3-yl)-1H-indol-3-yl)methylene)benzohydrazides and to investigate their apoptotic and anti-migratory potential in human breast adenocarcinoma cells as well as to examine their Bcl-2 and Bcl-xL protein binding ability via in silico docking. Hybrid 5g with a bromine atom in position-7 of coumarin ring displayed significant dose dependent cytotoxic activity with high selectivity to MCF-7 cells in MTT assay. Cell cycle progression analysis of 5g treated cells using flow cytometer exhibited a cell cycle arrest in the S phase and accumulation of cells in the subG1 phase. The apoptotic mode of cell death induced by 5g was further confirmed by Annexin-V staining assay. The wound healing assay revealed a profound impairment in the migration of MCF-7 cells presumably due to down-regulation of Bcl-2 and Bcl-xL proteins induced by 5g as observed in immunoblotting analysis. SAR studies of these hybrid molecules based on cell viability and docking were also probed. The most active pharmacophore 5g was found to bind favourably to Bcl-2 and Bcl-xL in docking simulation analysis suggesting it to be a probable small molecule Bcl-2/Bcl-xL inhibitor and a potential lead for breast cancer chemotherapy with apoptotic and anti-metastatic properties.

Synthesis and structure-activity relationship studies of novel 3,9-substituted α-carboline derivatives with high cytotoxic activity against colorectal cancer cells

In our continued focus on 1-benzyl-3-(5-hydroxymethyl-2-furyl)indazole (YC-1) analogs, we synthesized a novel series of 3,9-substituted α-carboline derivatives and evaluated the new compounds for antiproliferactive effects. Structure activity relationships revealed that a COOCH3 or CH2OH group at position-3 and substituted benzyl group at position-9 of the α-carboline nucleus were crucial for maximal activity. The most active compound, 11, showed high levels of cytotoxicity against HL-60, COLO 205, Hep 3B, and H460 cells with IC50 values of 0.3, 0.49, 0.7, and 0.8 μM, respectively. The effect of compound 11 on the cell cycle distribution demonstrated G2/M arrest in COLO 205 cells. Furthermore, mechanistic studies indicated that compound 11 induced apoptosis by activating death receptor and mitochondria dependent apoptotic signaling pathways in COLO 205 cells. The new 3,9-substituted α-carboline derivatives exhibited excellent anti-proliferative activities, and compound 11 can be used as a promising pro-apoptotic agent for future development of new antitumor agents.

Some new indole-coumarin hybrids; Synthesis, anticancer and Bcl-2 docking studies

Hybrid molecules have attracted attention for their improved biological activity, selectivity and lesser side effects profile, distinct from their individual components. In the quest for novel anticancer drug entities, three series of indole-coumarin hybrids - 3-(1-benzyl-1H-indol-2-yl)-2H-chromen-2-ones, 2-(2-oxo-2H-chromen-3-yl)-1H-indole-3-carbaldehydes and 2-(2-oxo-2H-chromen-3-yl)-1H-indole-3-carboxylic acids were synthesized. All the synthesized compounds were characterized by spectral techniques like IR, (1)H NMR, (13)C NMR, mass spectrometry and elemental analysis. In silico docking studies of synthesized molecules with apoptosis related gene Bcl-2 that is recognized to play an important role in tumerogenesis were carried out. Dose-dependent cytotoxic effect of the compounds in human breast adenocarcinoma (MCF-7) and normal cell lines were assessed using MTT assay and compared with that of the standard marketed drug, Vincristine. Compound 4c had a highly lipophilic bromine substituent capable of forming halogen bond and was identified as a potent molecule both in docking as well as cytotoxicity studies. Flow cytometric cell cycle analysis of 4c exhibited apoptotic mode of cell death due to cell cycle arrest in G2/M phase. Structure activity relationship of these hybrid molecules was also studied to determine the effect of steric and electronic properties of the substituents on cell viability.

Synthesis and biological evaluation of novel 3,9-substituted β-carboline derivatives as anticancer agents

In our previous studies on 1-benzyl-3-(5-hydroxymethyl-2-furyl)indazole (YC-1) analogs, we synthesised numerous substituted carbazole and α-carboline derivatives, which exhibited anticancer activity. In this study, we designed and synthesised a series of 3,9-substituted β-carbolines, by replacing the tricyclic rings of carbazole and α-carboline derivatives with isosteric β-carboline, and evaluated anticancer activity. We observed that 9-(2-methoxybenzyl)-β-carboline-3-carboxylic acid (11a) inhibited the growth of HL-60 cells by inducing apoptosis, with a half maximal inhibitory concentration of 4.0 μM. Our findings indicate that β-carboline derivatives can be used as lead compounds for developing novel antitumor agents.

Synthesis and SAR studies of novel 6,7,8-substituted 4-substituted benzyloxyquinolin-2(1H)-one derivatives for anticancer activity

BACKGROUND AND PURPOSE

4-Phenylquinolin-2(1H)-one (4-PQ) derivatives can induce cancer cell apoptosis. Additional new 4-PQ analogs were investigated as more effective, less toxic antitumour agents.

EXPERIMENTAL APPROACH

Forty-five 6,7,8-substituted 4-substituted benzyloxyquinolin-2(1H)-one derivatives were synthesized. Antiproliferative activities were evaluated using a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazoliun bromide assay and structure-activity relationship correlations were established. Compounds 9b, 9c, 9e and 11e were also evaluated against the National Cancer Institute-60 human cancer cell line panel. Hoechst 33258 and Annexin V-FITC/PI staining assays were used to detect apoptosis, while inhibition of microtubule polymerization was assayed by fluorescence microscopy. Effects on the cell cycle were assessed by flow cytometry and on apoptosis-related proteins (active caspase-3, -8 and -9, procaspase-3, -8, -9, PARP, Bid, Bcl-xL and Bcl-2) by Western blotting.

KEY RESULTS

Nine 6,7,8-substituted 4-substituted benzyloxyquinolin-2(1H)-one derivatives (7e, 8e, 9b, 9c, 9e, 10c, 10e, 11c and 11e) displayed high potency against HL-60, Hep3B, H460, and COLO 205 cancer cells (IC₅₀ < 1 μM) without affecting Detroit 551 normal human cells (IC₅₀ > 50 μM). Particularly, compound 11e exhibited nanomolar potency against COLO 205 cancer cells. Mechanistic studies indicated that compound 11e disrupted microtubule assembly and induced G2/M arrest, polyploidy and apoptosis via the intrinsic and extrinsic signalling pathways. Activation of JNK could play a role in TRAIL-induced COLO 205 apoptosis.

CONCLUSION AND IMPLICATIONS

New quinolone derivatives were identified as potential pro-apoptotic agents. Compound 11e could be a promising lead compound for future antitumour agent development.