Synthesis and in vitro antiproliferative evaluation of pyrimido[5,4-c]quinoline-4-(3H)-one derivatives

Comprehensive methodologies for synthesizing tricyclic fused pyrimidoquinolines of biological relevance: a review

Among quinoline-fused heterocycles, tricyclic pyrimidoquinoline nuclei have received considerable attention from synthetic chemists and medicinal and materials scientists over many years because they occur commonly in various biologically important natural products and potent drugs that exhibit anticancer, antibacterial, anti-inflammatory, antilipidemic, antioxidant and antimalarial activities. This study will be beneficial for medicinal chemists in the field of drug discovery to synthesize new fused tricyclic pyrimidoquinolines as potent therapeutic agents. This review provides a comprehensive compilation of the methodologies developed for the synthesis of all six known types of pyrimidoquinolines reported thus far. This article includes synthesis via solvent-free reactions, Vilsmeier-Haack reaction, Lewis and Brønsted acid catalysis, Pictet-Spengler reaction, the use of metal oxide nanoparticles as a green catalyst, multicomponent reactions (MCR), the use of l-proline as an environmentally friendly organocatalyst, aza-Wittig reaction, the use of β-cyclodextrin (β-CD) as a supramolecular catalyst, ultrasound irradiation, microwave-assisted reaction and ultraviolet light (UV365) irradiation. To the best of our knowledge, this is the first review that focuses on the synthesis of all six types of pyrimidoquinolines along with mechanistic aspects. Some medicinal applications are also mentioned.

Pyrimido[5,4-c]quinolines: Synthesis from 3,4-Di-functionallized Quinoline, Reactivity and Biological Activities

Quinoline and pyrimidine moieties are ubiquitous components in both natural and synthetic compounds, showcasing diverse applications. The fusion of these well-known structures into hybrid molecules has garnered attention due to their intriguing biological properties. Particularly in the field of medicinal chemistry, numerous studies in the last decade have focused on pyrimido[5,4-c]quinoline ring systems (PyQs5,4-c). This review elucidates the synthesis of PyQs5,4-c and their derivatives using 3,4-difunctionalized quinoline as a key starting material. The preparation of PyQs5,4-c involves a series of chemical transformations, including the Friedländer, Ullmann and Biginelli reaction, Vilsmeier-Haack formylation, Suzuki coupling, and a one-pot three-component reaction. These synthetic routes not only offer access to diverse PyQs5,4-c derivatives.

Discovery of new pyrimido[5,4-c]quinolines as potential antiproliferative agents with multitarget actions: Rapid synthesis, docking, and ADME studies

A novel series of pyrimido[5,4-c]quinoline derivatives variously substituted at positions 2 and 5 have been synthesized, in good to excellent yields, via rapid base-catalyzed cyclization reaction of 2,4-dichloroquinoline-3-carbonitrile (5) with guanidine hydrochlorides 6a-c. All the synthesized compounds were screened for their in vitro antiproliferative activity. The most active hybrids 26a-d, 28a-d, and 30B were assessed against topoisomerase (topo) I, topo IIα, CDK2, and EGFR. The majority of the tested compounds exhibited selective topo I inhibitory activity while had weak topo IIα inhibitory action with compounds 30B and 28d, showed better topo I inhibitory activity than the reference camptothecin. Compound 30B, the most potent derivative as antiproliferative agent, exhibited moderate activity against CDK2 (IC₅₀ = 1.60 µM). The results of this assay show that CDK2 is not a potential target for these compounds, implying that the observed cytotoxicity of these compounds is due to a different mechanism. Compounds 30B, 28d, and 28c were found to be the most potent against EGFR and their EGFR inhibitory activities (IC₅₀ = 0.40 ± 0.2, 0.49 ± 0.2, and 0.64 ± 0.3, respectively) relative to the positive control erlotinib (IC₅₀ = 0.07 ± 0.03 µM). These results revealed that topo I and EGFR are attractive targets for this class of chemical compounds.

Anti-tumor agents: Design, Synthesis, and Biological study of N-Substituted-7-hydroxy-1-azacoumarin-3-carboxamide derivatives as potent cytotoxic agents

Synthesis of ethyl 7-hydroxy-1-azacoumarin-3-carboxylate (3) was developed using ethyl-7-hydroxy coumarin-3-carboxylate and ammonium solution as the key synthons. Condensation of ethyl 7-hydroxy-1-azacoumarin-3-carboxylate with ammonium acetate and aniline to give N-substituted-7-hydroxy-1-azacoumarin-3-carboxamides (7-Hydroxy -1-azacoumarin-3-carboxamide (4) and N-phenyl 7-Hydroxy-1-azacoumarin-3-carboxamide (5)). Bromo derivative (N-phenyl 6, 8-dibromo-7-hydroxy-1-azacoumarin-3-carboxamide (6)) was obtained from halogenation of compound N-phenyl 7-Hydroxy-1-azacoumarin-3-carboxamide (5) with bromine in glacial acetic acid. N-phenyl-2,5-diacetoxy-6, 8-disubstituted-Quinoline-3-carboxamides (N-phenyl 2,7-diacetoxy-Quinoline-3-carboxamide (7) and N-phenyl 2,7-diacetoxy-6,8-dibromo-Quinoline-3-carboxamide (8)) were prepared via the acetylation of compounds 5 and 6 with acetic anhydride. Five compounds 4–8 were evaluated in vitro against more than one human tumor cell lines. Among the selected compounds, 6 showed the best in vitro cytotoxicity against the human cancer cell line; MCF-7 (with IC50 = 10.12 μM). In addition, cell cycle analysis of compound 6 demonstrated cell cycle arrest at G2/M phase and Pre-G1 apoptosis.

Evaluation of catacholase mimicking activity and apoptosis in human colorectal carcinoma cell line by activating mitochondrial pathway of copper(II) complex coupled with 2-(quinolin-8-yloxy)(methyl)benzonitrile and 8-hydroxyquinoline

To evaluate the cytotoxic potential of metal-based chemotherapeutic candidate towards the colorectal cancer, we have synthesized a new copper(II) complex [Cu(qmbn)(q)(Cl)] (1) (where, qmbn = 2-(quinolin-8-yloxy)(methyl)benzonitrile and q = 8-hydroxyquinoline) and structurally characterized by single crystal X-ray, Powder-XRD, FTIR and thermogravimetric analysis (TGA). The structural analysis reveals that copper(II) ions exist in a distorted square pyramidal (τ = ~0.1), with ligation of a chloride ion, oxygen atom and two nitrogen atoms at equatorial position and one oxygen atom at apical position. The cytotoxicity potential of complex 1 was executed against human colorectal cell lines (HCT116), which showed that 1 induces mitochondrion-mediated apoptotic cell death via activation of the Bax (pro-apoptotic protein) caspases-3 and 9 proteins. Interestingly, complex 1 was found to be a good candidate as electron-transfer catalyst which mimics catacholase with high turnover frequency (k_cat = 1.03 × 10² h^-1) for the conversion of the model substrate 3,5-di-tertbutylcatechol (3,5-DTBC) to 3,5-di-tertbutylquinone (3,5-DTBQ). Furthermore, molecular docking studies revealed that complex 1 was successfully localized inside the binding pocket of protein kinase (Akt), which validate the mechanism and mode of interaction of 1 that displayed cytotoxic activity experimentally. The obtained outcomes reveal that the complex 1 could be utilized as an encouraging perspective in the development of new therapeutic candidate for colon cancer.

Synthesis and evaluation of new sterol derivatives as potential antitumor agents

The current optimization of tetrazanbigen (TNBG) on the C-ring provided a series of new sterol derivatives 2a–2n. All new synthesized compounds were screened for their anti-proliferation activities against five human cancer cell lines (HepG2, QGY-7701, SMMC-7721, A-431 and NCI-H23 cell lines) in vitro. Among them, 2a, 2b, 2c, 2m and 2n exhibited high anti-proliferation activities on SMMC-7721, and their IC₅₀ values approach that of the positive control drug cisplatin. Compound 2a not only showed strong anti-proliferation activities against QGY-7701 and HepG2 cell lines, with IC₅₀ values (IC₅₀: 6.81 ± 0.24 μM, 7.69 ± 0.87 μM) better than that of cisplatin (IC₅₀: 8.75 μM, 18.89 ± 2.01 μM), but also exhibited good aqueous solubility (0.15–15 mg mL⁻¹ at pH 7.4 and 2.0). On the most sensitive QGY-7701 cell line, Oil red O staining and western blot analysis were performed. The results suggested that 2a can inhibit the growth of cancer cells possibly by interfering with the lipid metabolism balance of tumor cells, resulting in lipid accumulation and cell apoptosis (lipotoxicity). Moreover, after being treated with 2a, lipid accumulation of QGY-7701 cell was increased in a time and dose dependent manner. Based on these promising results, 2a was selected for drug formulation and further pre-clinical development.

The current optimization of tetrazanbigen (TNBG) on the C-ring provided a series of new sterol derivatives 2a–2n.

Superacidic Cyclization of Activated Anthranilonitriles into 2-Unsubstituted-4-aminoquinolines

4-Aminoquinolines were prepared in a three-step synthesis starting from substituted anthranilonitriles. The condensation on 1,1,1-trichloro-4-ethoxybut-3-enone proceeded efficiently either neat or in refluxing EtOH. Cyclization in superacidic trifluoromethanesulfonic acid provided unstable intermediate, which upon treatment with NaOEt in ethanol, afforded the expected esters. Theoretical investigations pointed out a monoprotonated nitrilium as the reactive species during the cyclization process.

Structure-activity relationship (SAR) study and design strategies of nitrogen-containing heterocyclic moieties for their anticancer activities

The present review article offers a detailed account of the design strategies employed for the synthesis of nitrogen-containing anticancer agents. The results of different studies describe the N-heterocyclic ring system is a core structure in many synthetic compounds exhibiting a broad range of biological activities. Benzimidazole, benzothiazole, indole, acridine, oxadiazole, imidazole, isoxazole, pyrazole, triazoles, quinolines and quinazolines including others drugs containing pyridazine, pyridine and pyrimidines are covered. The following studies of these compounds suggested that these compounds showed their antitumor activities through multiple mechanisms including inhibiting protein kinase (CDK, MK-2, PLK1, kinesin-like protein Eg5 and IKK), topoisomerase I and II, microtubule inhibition, and many others. Our concise representation exploits the design and anticancer potency of these compounds. The direct comparison of anticancer activities with the standard enables a systematic analysis of the structure-activity relationship among the series.

Identification of quinoline-chalcone hybrids as potential antiulcer agents

Antiulcer activity of novel quinoline-chalcone hybrids (13-37) was investigated. Among them, eight compounds (14, 16, 17, 23, 29, 31, 32 and 35) were found to be active in various ulcer models in Sprague-Dawley (SD) rats. To understand the mechanism of action of these hybrids, the effects of the compounds on antisecretory and cytoprotective activities were studied. All these active hybrids improved the depleted levels of mucin and consequently inhibited the formation of erosions in a pyloric ligated ulcer model. In addition, they also significantly increased the gastric PGE2 content in an aspirin induced ulcer model. The additional experiments including the in vitro metabolic stability and in vivo pharmacokinetics led to the identification of compound 17 as an orally active and safe candidate that is worthy of further investigation to be developed as an antiulcer agent.

A review on anticancer potential of bioactive heterocycle quinoline

The advent of Camptothecin added a new dimension in the field anticancer drug development containing quinoline motif. Quinoline scaffold plays an important role in anticancer drug development as their derivatives have shown excellent results through different mechanism of action such as growth inhibitors by cell cycle arrest, apoptosis, inhibition of angiogenesis, disruption of cell migration, and modulation of nuclear receptor responsiveness. The anti-cancer potential of several of these derivatives have been demonstrated on various cancer cell lines. In this review we have compiled and discussed specifically the anticancer potential of quinoline derivatives, which could provide a low-height flying bird's eye view of the quinoline derived compounds to a medicinal chemist for a comprehensive and target oriented information for development of clinically viable anticancer drugs.

Synthesis and antiproliferative evaluation of novel tetrahydrobenzo[4′,5′]thieno[3′,2′:5,6]pyrido[4,3-d]pyrimidine derivatives

A series of tetrahydrobenzo[4′,5′]thienophene[3′,2′:5,6]pyrido[4,3-d]pyrimidine-4-(3H)-one derivatives were synthesized and evaluated for their antiproliferative activities.

Synthesis of 8-hydroxyquinoline derivatives as novel antitumor agents

This letter describes the preparation of quinoline derivatives and their cytotoxic potentials toward human carcinoma cell lines. Among the selected compounds, 8-hydroxy-2-quinolinecarbaldehyde (3) showed the best in vitro cytotoxicity against the human cancer cell lines, including MDA231, T-47D, Hs578t, SaoS2, K562, SKHep1 (with a MTS50 range of 12.5-25 μg/mL) and Hep3B (with a MTS50 range of 6.25±0.034 μg/mL). The in vivo antitumor activity of compound 3 on subcutenaous Hep3B hepatocellular carcinoma xenograft in athymic nude mice was then studied. The results showed that the dose of 10 mg/kg/day of compound 3 with intraperitoneal injection for 9 days totally abolished the growth of the xenograft tumor of Hep3B with no histological damage on vital organs as compared with the control. The experimental results suggested that compound 3 has a good potential as an antitumor agent.