Design of β-carboline derivatives as DNA-targeting antitumor agents

Next generation antimitotic β-carboline derivatives modulate microtubule dynamics and downregulate NF-κB, ERK 1/2 and phospho HSP 27

AIM

Exploring the efficacy of β-carboline-based molecular inhibitors in targeting microtubules for the development of novel anticancer therapeutics.

MATERIALS AND METHODS

We synthesized a series of 1-Aryl-N-substituted-β-carboline-3-carboxamide compounds and evaluated their cytotoxicity against human lung carcinoma (A549) cells using the MTT assay. Normal lung fibroblast cells (WI-38) were used to assess compound selectivity. The mechanism of action of MJ-211 was elucidated through Western blot analysis of key pro-apoptotic and cell cycle regulatory proteins. Additionally, the inhibitory effect of MJ-211 on multicellular 3D spheroid growth of A549 cells was evaluated.

KEY FINDINGS

Lead compound MJ-211 exhibited remarkable cytotoxicity against A549 cells with an IC50 of 4.075 μM at 24 h treatment and IC50 of 1.7 nM after 72 h of treatment, while demonstrating selectivity towards normal WI-38 cells. MJ-211 activated pro-apoptotic factors Bim and p53, and suppressed Cyclin B1, Phospho HSP 27, BubR1, Mad 2, ERK1/2, and NF-κB, indicating its potent antimitotic and pro-apoptotic effects. MJ-211 significantly suppressed the migration of cells and inhibited the growth of A549 cell-derived multicellular 3D spheroids, highlighting its efficacy in a more physiologically relevant model.

SIGNIFICANCE

Cytotoxic effect of MJ-211 against cancer cells, selectivity towards normal cells, and ability to modulate key regulatory proteins involved in apoptosis and cell cycle progression underscore its potential as a promising template for further anticancer lead optimization. Moreover, the inhibitory effect of MJ-211 on multicellular spheroid growth suggests its efficacy in combating tumor heterogeneity and resistance mechanisms, thereby offering a promising avenue for future anticancer drug development.

3-Amide-β-carbolines block the cell cycle by targeting CDK2 and DNA in tumor cells potentially as anti-mitotic agents

β-Carboline alkaloids are natural and synthetic products with outstanding antitumor activity. C3 substituted and dimerized β-carbolines exert excellent antitumor activity. In the present research, 37 β-carboline derivatives were synthesized and characterized. Their cytotoxicity, cell cycle, apoptosis, and CDK2- and DNA-binding affinity were evaluated. β-Carboline monomer M3 and dimer D4 showed selective activity and higher cytotoxicity in tumor cells than in normal cells. Structure-activity relationships (SAR) indicated that the amide group at C3 enhanced the antitumor activity. M3 blocked the A549 (IC50 = 1.44 ± 1.10 μM) cell cycle in the S phase and inhibited A549 cell migration, while D4 blocked the HepG2 (IC50 = 2.84 ± 0.73 μM) cell cycle in the G0/G1 phase, both of which ultimately induced apoptosis. Furthermore, associations of M3 and D4 with CDK2 and DNA were proven by network pharmacology analysis, molecular docking, and western blotting. The expression level of CDK2 was downregulated in M3-treated A549 cells and D4-treated HepG2 cells. Moreover, M3 and D4 interact with DNA and CDK2 at sub-micromolar concentrations in endothermic interactions caused by entropy-driven adsorption processes, which means that the favorable entropy change (ΔS > 0) overcomes the unfavorable enthalpy change (ΔH > 0) and drives the spontaneous reaction (ΔG < 0). Overall, these results clarified the antitumor mechanisms of M3 and D4 through disrupting the cell cycle by binding DNA and CDK2, which demonstrated the potential of M3 and D4 as novel antiproliferative drugs targeting mitosis.

An overview of cdc2-like kinase 1 (Clk1) inhibitors and their therapeutic indications

Over the past decade, Clk1 has been identified as a promising target for the treatment of various diseases, in which deregulated alternative splicing plays a role. First small molecules targeting Clk1 are in clinical trials for the treatment of solid cancer, where variants of oncogenic proteins derived from alternative splicing promote tumor progression. Since many infectious pathogens hi-jack the host cell's splicing machinery to ensure efficient replication, further indications in this area are under investigation, such as Influenza A, HIV-1 virus, and Trypanosoma infections, and more will likely be discovered in the future. In addition, Clk1 was found to contribute to the progression of Alzheimer's disease through causing an imbalance of tau splicing products. Interestingly, homozygous Clk1 knockout mice showed a rather mild phenotype, opposed to what might be expected in view of the profound role of Clk1 in alternative splicing. A major drawback of most Clk1 inhibitors is their insufficient selectivity; in particular, Dyrk kinases and haspin were frequently identified as off-targets, besides the other Clk isoforms. Only few inhibitors were shown to be selective over Dyrk1A and haspin, whereas no Clk1 inhibitor so far achieved selectivity over the Clk4 isoform. In this review, we carefully compiled all Clk1 inhibitors from the scientific literature and summarized their structure-activity relationships (SAR). In addition, we critically discuss the available selectivity data and describe the inhibitor's efficacy in cellular models, if reported. Thus, we provide a comprehensive overview on the current state of Clk1 drug discovery and highlight the most promising chemotypes.

Design, synthesis and pharmacological evaluation of β-carboline derivatives as potential antitumor agent via targeting autophagy

A series of novel β-carboline derivatives was designed, synthesized and evaluated as potential anticancer agents. Among them, compound 6g showed the most potent antiproliferative activity against the 786-0, HT-29 and 22RV1 cell lines with IC₅₀ values of 2.71, 2.02, and 3.86 μM, respectively. The antitumor efficiency of compound 6gin vivo was also evaluated, and the results revealed that compound 6g significantly suppressed tumor development and reduced tumor weight in a mouse colorectal cancer homograft model. Further investigation on mechanisms of action demonstrated that compound 6g inhibited HCT116 cell growth by stimulating the ATG5/ATG7-dependent autophagic pathway. These molecules might be served as candidates for further development of colorectal cancer therapy agent.

Flavoprotein StnP2 Catalyzes the β-Carboline Formation during the Streptonigrin Biosynthesis

β-Carboline (βC) alkaloids constitute a large family of indole alkaloids that exhibit diverse pharmacological properties, such as antitumor, antiviral, antiparasitic, and antimicrobial activities. Here, we report that a flavoprotein StnP2 catalyzes the dehydrogenation at C1-N2 of a tetrahydro-β-carboline (THβC) generating a 3,4-dihydro-β-carboline (DHβC), and the DHβC subsequently undergoes a spontaneous dehydrogenation to βC formation involved in the biosynthesis of the antitumor agent streptonigrin. Biochemical characterization showed that StnP2 catalyzed the highly regio- and stereo-selective dehydrogenation, and StnP2 exhibits promiscuity toward different THβCs. This study provides an alternative kind of enzyme catalyzing the biosynthesis of βC alkaloids and enhances the importance of flavoproteins.

Harmicens, Novel Harmine and Ferrocene Hybrids: Design, Synthesis and Biological Activity

Cancer and malaria are both global health threats. Due to the increase in the resistance to the known drugs, research on new active substances is a priority. Here, we present the design, synthesis, and evaluation of the biological activity of harmicens, hybrids composed of covalently bound harmine/β-carboline and ferrocene scaffolds. Structural diversity was achieved by varying the type and length of the linker between the β-carboline ring and ferrocene, as well as its position on the β-carboline ring. Triazole-type harmicens were prepared using Cu(I)-catalyzed azide-alkyne cycloaddition, while the synthesis of amide-type harmicens was carried out by applying a standard coupling reaction. The results of in vitro biological assays showed that the harmicens exerted moderate antiplasmodial activity against the erythrocytic stage of P. falciparum (IC50 in submicromolar and low micromolar range) and significant and selective antiproliferative activity against the MCF-7 and HCT116 cell lines (IC50 in the single-digit micromolar range, SI > 5.9). Cell localization experiments showed different localizations of nonselective harmicene 36 and HCT116-selective compound 28, which clearly entered the nucleus. A cell cycle analysis revealed that selective harmicene 28 had already induced G1 cell cycle arrest after 24 h, followed by G2/M arrest with a concomitant drastic reduction in the percentage of cells in the S phase, whereas the effect of nonselective compound 36 on the cell cycle was much less pronounced, which agreed with their different localizations within the cell.

Morita–Baylis–Hillman reaction of 3-formyl-9H-pyrido[3,4-b]indoles and fluorescence studies of the products

β-Carboline is a privileged class of the alkaloid family and is associated with a broad spectrum of biological properties. 3-Formyl-9H-pyrido[3,4-b]indole is a such potent precursor belonging to this family which can be tailored for installing diversity at various positions of β-carboline to generate unique molecular hybrids of biological importance. The present work is a step towards this and assimilates the results related to the exploration of 3-formyl-9H-β-carbolines for the synthesis of β-carboline C-3 substituted MBH adducts followed by evaluation of their fluorescent characteristic. The effect of contact time, solvent system, concentration and substituents was also studied during investigation of fluorescence properties of these derivatives.

A comprehensive overview of β-carbolines and its derivatives as anticancer agents

β-Carboline alkaloids are a family of natural and synthetic products with structural diversity and outstanding antitumor activities. This review summarizes research developments of β-carboline and its derivatives as anticancer agents, which focused on both natural and synthetic monomers as well as dimers. In addition, the structure-activity relationship (SAR) analysis of β-carboline monomers and dimers are summarized and mechanism of action of β-carboline and its derivatives are also presented. A few possible research directions, suggestions and clues for future work on the development of novel β-carboline-based anticancer agents with improved expected activities and lesser toxicity are also provided.

Bioactive Tryptophan-Based Copper Complex with Auxiliary β-Carboline Spectacle Potential on Human Breast Cancer Cells: In Vitro and In Vivo Studies

Biocompatible tryptophan-derived copper (1) and zinc (2) complexes with norharmane (β-carboline) were designed, synthesized, characterized, and evaluated for the potential anticancer activity in vitro and in vivo. The in vitro cytotoxicity of both complexes 1 and 2 were assessed against two cancerous cells: (human breast cancer) MCF7 and (liver hepatocellular cancer) HepG2 cells with a non-tumorigenic: (human embryonic kidney) HEK293 cells. The results exhibited a potentially decent selectivity of 1 against MCF7 cells with an IC50 value of 7.8 ± 0.4 μM compared to 2 (less active, IC50 ~ 20 μM). Furthermore, we analyzed the level of glutathione, lipid peroxidation, and visualized ROS generation to get an insight into the mechanistic pathway and witnessed oxidative stress. These in vitro results were ascertained by in vivo experiments, which also supported the free radical-mediated oxidative stress. The comet assay confirmed the oxidative stress that leads to DNA damage. The histopathology of the liver also ascertained the low toxicity of 1.

β-Carbolines as potential anticancer agents

β-Carbolines are indole alkaloids having a tricyclic pyrido[3,4-b]indole ring in their structure. Since the isolation of first β-carboline from Peganum harmala in 1841, the isolation and synthesis of various β-carboline derivatives surged in the following centuries. β-Carboline derivatives due to their widespread availability from natural sources, structural flexibility, quick reactivity and interaction with varied anticancer targets such as DNA (intercalation, groove binding, etc.), enzymes (GPX4, topoisomerases, kinases, etc.) and proteins (tubulin, ABCG2/BRCP1, etc.) have established themselves as promising lead compounds for the synthesis of various anticancer active agents. The current review covers the synthesis and isolation, anticancer activity, mechanism of action and SAR of various β-carboline containing molecules, its derivatives and congeners.

Bioinspired imidazo[1,2-a:4,5-c']dipyridines with dual antiproliferative and anti-migrative properties in human cancer cells: The SAR investigation

Herein, we report the design, synthesis and evaluation of novel bioinspired imidazo[1,2-a:4,5c']dipyridines. The structural optimization identified four anti-proliferative compounds. Compounds 11, 18, 19 and 20 exhibited excellent anticancer activities in vitro with IC₅₀ of 0.4-5 μM against three human cancer cell lines (MDA-MB-468, MDA-MB-435s and MDA-MB-231). These four compounds induced apoptosis in MDA-MB-231 cells in a dose-dependent manner, targeting different apoptotic proteins expression: 11 increased the expression of pro-apoptotic Bax protein while 18-20 reduced the level of anti-apoptotic Bcl-2 protein. Compounds 18 and 19 also reduced MDA-MB-231 cells proliferation as measured by Ki-67 staining. Furthermore, compounds were also tested for the ability to inhibit cell migration in the highly aggressive human MDA-MB-435s cell line. Six compounds of this series (8, 15, 18, 22, 23, 24) inhibited cell migration by 41-50% while four compounds (20, 25, 27, 30) inhibited the migration by 53-62% in wound-healing experiments. Interestingly, compound 20 presented both antiproliferative and anti-migration activities and might be a promising anti-metastatic agent for cancer treatment.

Structure-activity insights of harmine targeting DNA, ROS inducing cytotoxicity with PARP mediated apoptosis against cervical cancer, anti-biofilm formation and in vivo therapeutic study

Harmine exhibits pH dependent structural equilibrium and possesses numerous biological and pharmacological activities. Mode and mechanism of DNA binding and its cytotoxicity were studied by multiple spectroscopic, calorimetric, molecular docking and in vitro apoptotic as well as in vivo biochemical and histological studies. It exists as cationic (structure I) and decationic form (structure II) in the pH range 3.0-7.8 and 8.5-12.4, respectively, with a pK_a of 8.0. Structure I at pH 6.8 binds strongly to DNA with a cooperative mode of binding of K_iω 1.03 × 10⁶ M^-1and stoichiometry of 5.0 nucleotide phosphates. Structure I stabilized DNA by 10 °C, showed85%quenching of fluorescence intensity, perturbation in circular dichroism, partial intercalation and enthalpy driven exothermic binding. While, structure II at pH 8.5 has very weak interaction with CT DNA. Cytotoxic potencies of structure I was tested on four different cancer cell lines along with normal embryonic cell. It showed maximum cytotoxicity with GI₅₀of 20 µM, against HeLa causing several apoptotic induction abilities. Harmine exhibited G2M arrest with ROS induced effective role in PARP mediated apoptosis as well as anti-inflammatory action on HeLa cells. Harmine further presented MIC and antibiofilm activity against Staphylococcus aureus in presence of <160 and 30 µg/ml, respectively. Mice with post harmine treatment (30 mg/kg b.w., I.P.) showed maximum recovery from damaged to near normal architecture of cervical epithelial cells. This study may be of prospective use in a framework to design novel beta carboline compounds for improved therapeutic applications in future against cervical cancer. HighlightsHarmine exists in structure I and structure II forms in the pH 6.8 and 8.5with a pK_a of 8.0.Structure I at pH 6.8 binds strongly to DNA compared to structure II.Structure I showed maximum cytotoxicity with GI₅₀ of 20 µM against HeLa.ROS mediated cytotoxicitywithG2M arrest with PARP mediated apoptosis was studied.Harmine (30µg/ml) exhibited antibiofilm activity against Staphylococcus aureus.Post harmine dose (30 mg/kg b.w., I.P.) in mice showed recovery of cervical epithelial cells.Communicated by Ramaswamy H. Sarma.

Pd(0)-Catalyzed Intramolecular Heck reaction of 2/3-Aryl(amino)methyl-3/2-bromoindoles: Syntheses of 3,4-Benzo[c]-β-carbolines, Benzo[4,5]isothiazolo[2,3-a]indole 5,5-Dioxides, and 1,2-Benzo[a]-γ-carbolines

One-pot synthesis of 3,4-benzo[c]-β-carbolines was achieved from 2-aryl(tosylamino)methyl-3-bromoindoles via 10 mol % Pd(OAc)₂/PPh₃-mediated intramolecular Heck coupling using K₂CO₃ as a base in DMF at 110 °C with concomitant aromatization through an elimination of tosylsulfinic acid. Under identical conditions, the isomeric 3-aryl(tosylamino)methyl-2-bromoindoles upon intramolecular Heck reaction furnished benzo[4,5]isothiazolo[2,3-a]indole 5,5-dioxides instead of the expected γ-carbolines. However, synthesis of the expected γ-carboline framework, 3-tosyl-6,9-dihydro-1,2-benzo[a]-γ-carbolines, could be achieved from 3-aryl(tosylamino)methyl-2-bromoindoles containing a mesitylene sulfonyl unit as a protecting group on the indole nitrogen.

Design, synthesis and antitumour evaluation of pyrrolo[1,2-f]-phenanthridine and dibenzo[f,h]pyrrolo[1,2-b]isoquinoline derivatives

A series of 1,2-bis(hydroxymethyl)pyrrolo[1,2-f]phenanthridine derivatives and their alkyl (ethyl and isopropyl) carbamates and 12,13-bis(hydroxymethyl)-9,14-dihydro-dibenzo[f,h]pyrrolo[1,2-b]isoquinoline derivatives were synthesized for antiproliferative evaluation. The preliminary antitumour studies revealed that these two types of bis(hydroxymethyl) derivatives showed significant antitumour activities and were able to inhibit the growth of various human tumour cell lines in vitro. Several of the derivatives were demonstrated to cause DNA interstrand cross-links by an alkaline agarose gel shifting assay. These conjugates were cytotoxic to a variety of cancer cell lines by inducing DNA damage, delaying cell cycle progression in the G2/M phase and triggering apoptosis. Compound 21a, dissolved in a vehicle suitable for intravenous administration, was selected for antitumour studies in animal models. We demonstrated that at a dose that did not cause body weight loss in mice, compound 21a could significantly suppress the growth of tumour xenografts of human lung cancer H460 and colorectal cancer HCT-116 cells in nude mice. Our present results confirm the antitumour activities of these conjugates.

Synthetic carboline compounds targeting protein: biophysical and biological perspective

Pictet-Spengler cyclization method has been adopted for the synthesis of three carboline derived compounds: two compounds with tetrahydro gama- and beta-having CF₃ group and amino alkyl chain at delta and alpha position, respectively, and another with guanidine alkyl chain at alpha-position. Structure-activity relationship of the analogues with human serum albumin was studied by fluorescence and Fourier-transform infrared spectroscopy  followed by molecular docking. The data showed maximum affinity of human serum albumin with comp7 (S0-820) followed by comp3 (S0-1040) and least with comp1 (S0-728). The compounds were tested for cytotoxic potencies. Comp3, showed maximum cytotoxicity with GI₅₀ 6.2 µM, against HCT-116, followed by comp7, and poor cytotoxicity with comp1. Comp3 and 7 induced oxidative stress mediated autophagy led programmed cell death in HCT-116. Furthermore, the compounds effectively inhibit DNA topoisomerase I activity and showed anti-inflammatory actions. In vivo studies regarding therapeutic protective action of Comp3, as a representative carboline analogue, against colon toxicant, 1,2-dimethylhydrazine dihydrochloride (DMH), showed the efficacy of the compound against organ toxicity. The existing studies on biological evaluation showed that these synthetic compounds may have a major role as anticancer agents having myriad of proven therapeutic applications. Communicated by Ramaswamy H. Sarma.

Metal-free propargylation/aza-annulation approach to substituted β-carbolines and evaluation of their photophysical properties

An efficient acid-catalyzed propargylation/aza-annulation sequence was developed under metal-free reaction conditions, thus leading to a one-pot synthesis of a variety of substituted β-carbolines starting from propargylic alcohols and indole 2-carbonyls. This versatile strategy was further extended to the synthesis of 5-azaindoles and 5-azabenzothiazoles. Optical properties suggested that manipulation of electron donor and acceptor moieties on β-carbolines has an impact on their ground and excited state electronic behavior. This leads to blue or green emission and should facilitate the development of organic light emitting diodes (OLEDs). Electrochemical and stability studies revealed that 4a-6 shows ease of redox activity and photostability during illumination.

A transition metal-free approach towards synthesis of β-carboline tethered 1,3,4-oxadiazoles via oxidative C–O bond formation

An efficient protocol has been developed for one-pot synthesis of biologically interesting β-carboline substituted 1,3,4-oxadiazoles via an I₂-assisted oxidative C–O bond formation strategy.

An AcOH-mediated metal free approach towards the synthesis of bis-carbolines and imidazopyridoindole derivatives and assessment of their photophysical properties

A concise, atom-economical and environmentally sustainable tandem strategy has been formulated to access highly fluorescent (Φ_F up to 40%) target molecules via the formation of three C–N bonds in a single operation.

Norharmane as a potential chemical entity for development of anticancer drugs

Cancer is a leading cause of death generally, and to overcome this problem the introduction of a new drug developing is a continuous endeavour. An alkaloid, norharmane and its derivatives, which have anticancer activities, widely distributed in several living and synthetic chemical sources. Herewith, the suggested mechanisms of organic reactions and synthetic approaches of norharmane available so far were considered. Active sites of norharmane nucleus positions, C-1, C-3, and N-9, were used for developing new molecules and based on structure activity relationship (SAR), those have been seen with anticancer activities. This review summarizes on chemistry of synthetic strategies of norharmane derivatives, which may provide a framework to design a novel anticancer drug, in future.

Synthesis and In Vitro Antitumor Activity of Novel Bivalent β-Carboline-3-carboxylic Acid Derivatives with DNA as a Potential Target

A series of novel bivalent β-carboline derivatives were designed and synthesized, and in vitro cytotoxicity, cell apoptosis, and DNA-binding affinity were evaluated. The cytotoxic results demonstrated that most bivalent β-carboline derivatives exhibited stronger cytotoxicity than the corresponding monomer against the five selected tumor cell lines (A549, SGC-7901, Hela, SMMC-7721, and MCF-7), indicating that the dimerization at the C³ position could enhance the antitumor activity of β-carbolines. Among the derivatives tested, 4B, 6i, 4D, and 6u displayed considerable cytotoxicity against A549 cell line. Furthermore, 4B, 6i, 4D, and 6u induced cell apoptosis in a dose-dependent manner, and caused cell cycle arrest at the S and G2/M phases. Moreover, the levels of cytochrome C in mitochondria, and the expressions of bcl-2 protein, decreased after treatment with β-carbolines, which indicated that 6i and 6u could induce mitochondria-mediated apoptosis. In addition, the results of UV-visible spectral, thermal denaturation, and molecular docking studies revealed that 4B, 6i, 4D, and 6u could bind to DNA mainly by intercalation.

A review on traditional uses, phytochemistry, pharmacology, pharmacokinetics and toxicology of the genus Peganum

ETHNOPHARMACOLOGICAL RELEVANCE

The plants of the genus Peganum have a long history as a Chinese traditional medicine for the treatment of cough, hypertension, diabetes, asthma, jaundice, colic, lumbago, and many other human ailments. Additionally, the plants can be used as an amulet against evil-eye, dye and so on, which have become increasingly popular in Asia, Iran, Northwest India, and North Africa.

AIM OF THE REVIEW

The present paper reviewed the ethnopharmacology, phytochemistry, analytical methods, biological activities, metabolism, pharmacokinetics, toxicology, and drug interaction of the genus Peganum in order to assess the ethnopharmacological use and to explore therapeutic potentials and future opportunities for research.

MATERIALS AND METHODS

Information on studies of the genus Peganum was gathered via the Internet (using Google Scholar, Baidu Scholar, Elsevier, ACS, Pudmed, Web of Science, CNKI and EMBASE) and libraries. Additionally, information was also obtained from some local books, PhD and MS's dissertations.

RESULTS

The genus Peganum has played an important role in traditional Chinese medicine. The main bioactive metabolites of the genus include alkaloids, flavonoids, volatile oils, etc. Scientific studies on extracts and formulations revealed a wide range of pharmacological activities, such as cholinesterase and monoamine oxidase inhibitory activities, antitumor, anti-hypertension, anticoagulant, antidiabetic, antimicrobial, insecticidal, antiparasidal, anti-leishmaniasis, antioxidant, and anti-inflammatory.

CONCLUSIONS

Based on this review, there is some evidence for extracts' pharmacological effects on Alzheimer's and Parkinson's diseases, cancer, diabetes, hypertension. Some indications from ethnomedicine have been confirmed by pharmacological effects, such as the cholinesterase, monoamine oxidase and DNA topoisomerase inhibitory activities, hypoglycemic and vasodilation effects of this genus. The available literature showed that most of the activities of the genus Peganum can be attributed to the active alkaloids. Data regarding many aspects of the genus such as mechanisms of actions, metabolism, pharmacokinetics, toxicology, potential drug interactions with standard-of-care medications is still limited which call for additional studies particularly in humans. Further assessments and clinical trials should be performed before it can be integrated into medicinal practices.

In(OTf)3 assisted synthesis of β-carboline C-3 tethered imidazo[1,2-a]azine derivatives

Synthesis of β-carboline based natural products and synthetic derivatives is one of the frontier areas of research owing to their medicinal properties.

Asymmetric synthesis of CF3- and indole-containing tetrahydro-β-carbolines via chiral spirocyclic phosphoric acid-catalyzed aza-Friedel–Crafts reaction

An enantioselective aza-Friedel–Crafts reaction of indoles with 1-trifluoromethyl-3,4-dihydro-β-carbolines has been developed to afford tetrahydro-β-carbolines with a CF₃- and indole-containing quaternary stereocenter by using chiral phosphoric acid catalysis.

A Potent Derivative of Indolizino[6,7-b]Indole for Treatment of Human Non-Small Cell Lung Cancer Cells

The therapeutic effect in non–small cell lung cancer (NSCLC) patients is limited because of intrinsic and acquired resistance. Thus, an unmet need exists for the development of new drugs to improve the therapeutic efficacy in NSCLC patients. In this study, the novel small molecule indolizino[6,7-b]indole derivative BO-1978 was selected to evaluate its therapeutic effects on NSCLC and its preclinical toxicity in animal models. An in vitro cytotoxicity assay revealed that BO-1978 significantly suppressed the growth of various NSCLC cell lines with or without mutations in epidermal growth factor receptor (EGFR). Mechanistically, we demonstrated that BO-1978 exhibited multiple modes of action, including inhibition of topoisomerase I/II and induction of DNA cross-linking. Treatment of NSCLC cells with BO-1978 caused DNA damage, disturbed cell cycle progression, and triggered apoptotic cell death. Furthermore, BO-1978 significantly suppressed the growth of EGFR wild-type and mutant NSCLC tumors in xenograft tumor and orthotopic lung tumor models with negligible body weight loss. The combination of BO-1978 with gefitinib further suppressed EGFR mutant NSCLC cell growth in xenograft tumor and orthotopic lung tumor models. Preclinical toxicity studies showed that BO-1978 administration did not cause apparent toxicity in mice. Based on its significant therapeutic efficacy and low drug toxicity, BO-1978 is a potential therapeutic agent for treatment of NSCLC.

In(OTf)3 catalysed an expeditious synthesis of β-carboline–imidazo[1,2-a]pyridine and imidazo[1,2-a]pyrazine conjugates

β-Carboline containing alkaloids are ubiquitously present in Nature, while an imidazo[1,2-a]pyridine nucleus is incorporated in various synthetic commercial drugs and biologically previliged moieties.