Recent advances in the chemistry of 2-chloroquinoline-3-carbaldehyde and related analogs

Design, Synthesis and Molecular Docking Studies of Pyrazoline Derivatives as PI3K Inhibitors

AIM

Design, synthesis and molecular docking studies of quinoline/naphthalene containing pyrazoline derivatives as PI3K inhibitors.

BACKGROUND

Phosphatidylinositol 3-kinases (PI3Ks) belong to the family of enzymes, which are associated with various cellular functions such as cell growth, proliferation, differentiation etc. Overexpression or any changes in these functions may result in various abnormalities, which in turn cause cancer.

OBJECTIVES

To perform synthesis and molecular docking studies of quinoline/naphthalene containing pyrazoline derivatives as PI3K inhibitors.

METHODS

2-Chloroquinoline-3-carbaldehyde was synthesized by a reaction of acetanilide and POCl3. The latter was reacted with substituted acetophenones to synthesize chalcones, which were reacted with substituted phenyl hydrazines to yield pyrazoline derivatives (Series I). Similarly, pchloro benzaldehyde was reacted with 2-acetonapthone to yield chalcone with substituted phenyl hydrazines to yield pyrazoline derivatives (Series II).

RESULTS

The synthetic compounds were subjected to molecular modelling experiments using Schrodinger 2016 software and evaluated in silico for their PI3K binding affinities. All the compounds had better docking scores than AMG-319 (-4.36 Kcal/mol) and comparable docking scores with PI-103 (-6.83 Kcal/mol).

CONCLUSION

Compounds 5 and 3 had the best docking scores (-7.85 and -7.17 Kcal/mol, respectively). The synthesized compounds have better docking scores than the reference drug AMG-319. As a result, they might be used as lead molecules in investigating PI3K inhibitors.

Discovery of new pyridine-quinoline hybrids as competitive and non-competitive PIM-1 kinase inhibitors with apoptosis induction and caspase 3/7 activation capabilities

New quinoline-pyridine hybrids were designed and synthesised as PIM-1/2 kinase inhibitors. Compounds 5b, 5c, 6e, 13a, 13c, and 14a showed in-vitro low cytotoxicity against normal human lung fibroblast Wi-38 cell line and potent in-vitro anticancer activity against myeloid leukaemia (NFS-60), liver (HepG-2), prostate (PC-3), and colon (Caco-2) cancer cell lines. In addition, 6e, 13a, and 13c significantly induced apoptosis with percentage more than 66%. Moreover, 6e, 13a, and 13c significantly induced caspase 3/7 activation in HepG-2 cell line. Furthermore, 5c, 6e, and 14a showed potent in-vitro PIM-1 kinase inhibitory activity. While, 5b showed potent in-vitro PIM-2 kinase inhibitory activity. Kinetic studies using Lineweaver-Burk double-reciprocal plot indicated that 5b, 5c, 6e, and 14a behaved as competitive inhibitors while 13a behaved as both competitive and non-competitive inhibitor of PIM-1 kinase enzyme. Molecular docking studies indicated that, in-silico affinity came in coherence with the observed in-vitro inhibitory activities against PIM-1/2 kinases.

Pyrrolizine/indolizine-bearing (un)substituted isoindole moiety: design, synthesis, antiproliferative and MDR reversal activities, and in silico studies

Two new series of pyrrolizine/indolizine derivative-bearing (un)substituted isoindole moiety were designed and synthesized. The anticancer potential of the new compounds was evaluated against hepatocellular carcinoma (HepG-2), colorectal carcinoma, colon cancer (HCT-116), and breast cancer (MCF-7) cell lines. Compounds 6d and 6o were the most potent derivatives with IC50 values ranging from 6.02 to 13.87 μM against HePG-2, HCT-116, and MCF-7 cell lines. Moreover, methyl analog of the fluoro-substituted indolizine derivative 6m revealed significant antiproliferative activity against HePG-2, HCT-116, and MCF-7 cancer cell lines with IC50 values of 11.97, 28.37, and 19.87 μM, respectively. The most active anticancer analogs, 6d, 6m, and 6o, were inspected for their putative mechanism of action by estimating their epidermal growth factor receptor (EGFR) and cyclin-dependent kinase (CDK 2) inhibitory activities. Thus, compound 6o displayed the most inhibitory activity against EGFR and CDK 2 with IC50 values of 62 and 118 nM, respectively. Additionally, the quantitative real-time PCR analysis for the P-glycoprotein effect of compounds 6d, 6m, and 6o was performed, in which compound 6o illustrated significant down-regulation of P-gp against the HepG-2 cell line by 0.2732 fold. Mechanistic studies for the most active compounds involving the reversal doxorubicin (DOX) effect of compounds 6d, 6m, and 6o were performed, which illustrated cytotoxic activity with IC50 22.27, 3.88, and 8.79 μM, respectively. Moreover, the apoptotic activity of the most active derivative 6o on HCT-116 cancer cells showed accumulation in the G1 and S phases of the cell cycle.

The regioselective one-pot four-component synthesis of novel functionalized 4H-pyrano[2, 3-b]quinoline derivatives using DABCO as a homogeneous organocatalyst

This study deals with the synthesis of the regioselective and facile domino one-pot four-component reaction of 2-chloroquinoline-3-carbaldehydes, 1, 3-cyclodione compounds (as cyclic active methylene), ethyl acetoacetate (as β-keto ester), and hydrazine hydrate in the presence of DABCO as a homogeneous organocatalyst yielding a novel series of 4H-pyrano[2, 3-b]quinolones. This multicomponent reaction has some advantages; the significant one is C-O bond formation under metal-free conditions. Other benefits include simple procedure, mild and green condition, high yield, easy purification, and excellent regioselectivity. All polycyclic products (7a-k, 11 new compounds) were characterized by IR, 1H NMR, 13C NMR, and mass spectra.

Development of 2-chloroquinoline based heterocyclic frameworks as dual inhibitors of SARS-CoV-2 MPro and PLPro

Evolution of new variants of SARS-CoV-2 warrant the need for the continued efforts in identifying target-oriented new drugs. Dual targeting agents against M^Pro and PL^Pro not only overcome the incomplete efficacy but also the drug resistance, which is common problem. Since both these are cysteine proteases, we designed 2-chloroquinoline based molecules with additional imine moiety in the middle as possible nucleophilic warheads. In the first round of design and synthesis, three molecules (C3, C4 and C5) inhibited (Ki < 2 μM) only M^Pro by binding covalently to C145 and one molecule (C10) inhibited both the proteases non-covalently (Ki < 2 μM) with negligible cytotoxicity. Further conversion of the imine in C10 to azetidinone (C11) improved the potency against both the enzymes in the nanomolar range (820 nM against M^Pro and 350 nM against PL^Pro) with no cytotoxicity. Conversion of imine to thiazolidinone (C12), reduced the inhibition by 3-5 folds against both the enzymes. Biochemical and computational studies suggest that C10-C12 bind in the substrate binding pocket of M^Pro and in the BL2 loop of the PL^Pro. Since these dual inhibitors have least cytotoxicity, they could be further explored as therapeutics against the SARS-CoV-2 and other analogous viruses.

Quinoline Derivatives with Different Functional Groups: Evaluation of Their Catecholase Activity

In this work, we are interested in finding new catalysts for catecholase, whose principle is based on the oxidation reaction of catechol to o-quinone. In this context, we have studied a series of seven quinoline-based compounds. The present work indicates that the complexes formed between seven selected quinoline compounds and the copper salts viz. Cu(OAc)2, CuSO4, Cu(NO3)2, and CuCl2 elicit catalytic activities for the oxidation of catechol to o-quinone. The complexes formed with the Cu(OAc)2 salt show a much higher catalytic activity than the others, whereas the Cu(NO3)2 and CuCl2 salts formed complexes with low catalytic activity. This study also shows that the oxidation rate depends on two factors, namely the chemical structure of the ligands and the nature of the ions coordinated with the copper.

Synthesis, in silico molecular docking analysis, pharmacokinetic properties and evaluation of antibacterial and antioxidant activities of fluoroquinolines

BACKGROUND

Quinolines have demonstrated various biological activities such as antimalarial, antibacterial and anticancer. Hence, compounds with such scaffold have been used as lead in drug development. This project is, therefore, aimed to synthesis and evaluates some biological activities of quinoline analogs.

METHODS

2-Chloro-7-fluoroquinoline-3-carbaldehydes were synthesized by the application of Vilsmeier-Haack reaction. The chlorine in the fluoroquinoline-3-carbaldehyde was replaced with various nucleophiles. The aldehyde functional group was also converted to carboxylic acid and imine groups using oxidizing agent and various amines, respectively. The structures of the compounds synthesized were characterized by spectroscopic methods. Disc diffusion and DPPH assays were used to evaluate the antibacterial and antioxidant activities, respectively. The in silico molecular docking analysis of the synthesized compounds were done using AutoDock Vina against E. coli DNA Gyrase B and human topoisomerase IIα. The drug likeness properties were assessed using SwissADME and PreADMET.

RESULTS

Nine novel quinoline derivatives were synthesized in good yields. The in vitro antibacterial activity of the synthesized compounds was beyond 9.3 mm inhibition zone (IZ). Compounds 4, 5, 6, 7, 8, 10, 15, and 16 exhibited activity against E. coli, P. aeruginosa, S. aureus and S. pyogenes with IZ ranging from 7.3 ± 0.67 to 15.3 ± 0.33 mm at 200 μg/mL. Compound 9 displayed IZ against three of the bacterial strains except S. aureus. The IC50 for the radical scavenging activity of the synthesized compounds were from 5.31 to 16.71 μg/mL. The binding affinities of the synthesized compounds were from - 6.1 to - 7.2 kcal/mol against E. coli DNA gyrase B and - 6.8 to - 7.4 kcal/mol against human topoisomerase IIα. All of the synthesized compounds obeyed Lipinski's rule of five without violation.

CONCLUSION

Compounds 4, 5, 6, 7, 8, 10, 15, and 16 displayed activity against Gram positive and Gram negative bacterial strains indicating that these compounds might be used as broad spectrum bactericidal activity. Compound 8 (13.6 ± 0.22 mm) showed better IZ against P. aeruginosa compared with ciprofloxacin (10.0 ± 0.45 mm) demonstrating the potential of this compound as antibacterial agent against this strain. Compounds 5, 6, 7, 8, 9 and 10 showed comparable binding affinities in their in silico molecular docking analysis against E. coli DNA gyrase B. All of the synthesized compounds also obeyed Lipinski's rule of five without violation which suggests these compounds as antibacterial agents for further study. Compounds 7 and 8 were proved to be a very potent radical scavenger with IC50 values of 5.31 and 5.41 μg/mL, respectively. Compound 5, 6, 8, 10 and 16 had comparable binding affinity against human topoisomerase IIα suggesting these compounds as a possible candidate for anticancer drugs.

Synthesis and Evaluation of the Antibacterial and Antioxidant Activities of Some Novel Chloroquinoline Analogs

Quinoline heterocycle is a useful scaffold to develop bioactive molecules used as anticancer, antimalaria, and antimicrobials. Inspired by their numerous biological activities, an attempt was made to synthesize a series of novel 7-chloroquinoline derivatives, including 2,7-dichloroquinoline-3-carbonitrile (5), 2,7-dichloroquinoline-3-carboxamide (6), 7-chloro-2-methoxyquinoline-3-carbaldehyde (7), 7-chloro-2-ethoxyquinoline-3-carbaldehyde (8), and 2-chloroquinoline-3-carbonitrile (12) by the application of Vilsmeier–Haack reaction and aromatic nucleophilic substitution of 2,7-dichloroquinoline-3-carbaldehyde. The carbaldehyde functional group was transformed into nitriles using POCl3 and NaN3, which was subsequently converted to amide using CH3CO2H and H2SO4. The compounds synthesized were screened for their antibacterial activity against Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, and Streptococcus pyogenes. Compounds 6 and 8 showed good activity against E. coli with an inhibition zone of 11.00 ± 0.04 and 12.00 ± 0.00 mm, respectively. Compound 5 had good activity against S. aureus and P. aeruginosa with an inhibition zone of 11.00 ± 0.03 mm relative to standard amoxicillin (18 ± 0.00 mm). Compound 7 displayed good activity against S. pyogenes with an inhibition zone of 11.00 ± 0.02 mm. The radical scavenging activity of these compounds was evaluated using 1,1-diphenyl-2-picrylhydrazyl (DPPH), and compounds 5 and 6 displayed the strongest antioxidant activity with IC50 of 2.17 and 0.31 µg/mL relative to ascorbic acid (2.41 µg/mL), respectively. The molecular docking study of the synthesized compounds was conducted to investigate their binding pattern with topoisomerase IIβ and E. coli DNA gyrase B. Compounds 6 (−6.4 kcal/mol) and 8 (−6.6 kcal/mol) exhibited better binding affinity in their in silico molecular docking against E. coli DNA gyrase. The synthesized compounds were also found to have minimum binding energy ranging from −6.9 to −7.3 kcal/mol against topoisomerase IIβ. The SwissADME predicted results showed that the synthesized compounds 5–8 and 12 satisfy Lipinski’s rule of five with zero violations. The ProTox-II predicted organ toxicity results revealed that all the synthesized compounds were inactive in hepatotoxicity, immunotoxicity, mutagenicity, and cytotoxicity. The findings of the in vitro antibacterial and molecular docking analysis suggested that compound 8 might be considered a hit compound for further analysis as antibacterial and anticancer drug. The radical scavenging activity displayed by compounds 5 and 6 suggests these compounds as a radical scavenger.

Synthesis of (2-chloroquinolin-3-yl)-1,3,4-thiadiazole-2-carboxamides

(2-Chloroquinolin-3-yl)-1,3,4-thiadiazole-2-carboxamides were synthesized from hydrazones obtained via the reaction of 3-formyl-2-chloroquinoline with oxamic acid thiohydrazides.

Synthesis, Antibacterial, Antioxidant, and Molecular Modeling Studies of Novel [2,3′-Biquinoline]-4-Carboxylic Acid and Quinoline-3-Carbaldehyde Analogs

Currently, it has been common to see people being affected and dying from untreatable infections caused by multidrug-resistant (MDR) germs. To tackle this problem, developing new effective chemotropic agents is urgently needed. Hence, this project aims to design, synthesize, and evaluate their antibacterial and antioxidant activities of new series of [2,3′-biquinoline]-4-carboxylic acid and quinoline-3-carbaldehyde analogs. The molecular docking analysis of the compounds against E. coli DNA gyrase was computed to investigate the binding mode of the compounds within the active site of the enzyme. In this regard, a new series of [2,3′-biquinoline]-4-carboxylic acid and quinoline-3-carbaldehyde analogs were synthesized by utilization of Vilsmeier–Haack, Doebner, nucleophilic substitution, and hydrolysis reactions. The structures of the synthesized compounds were determined using UV-Vis, FT-IR, and NMR. The synthesized compounds were screened for their antibacterial activity against four bacterial strains using disc diffusion methods. The findings of the study revealed that seven of synthetic compounds possess good antibacterial activity compared to ciprofloxacin which was used as a positive control in the experiment. Among them, compounds 4, 9, and 10 displayed the highest mean inhibition zone of 13.7 ± 0.58, 16.0 ± 1.7, and 20.7 ± 1.5 mm, respectively, at 0.1 μg/μL. The radical scavenging property of these compounds was evaluated using DPPH radical assay where compounds 9 and 20 showed the strongest activity with IC50 values of 1.25 and 1.75 μg/mL, respectively. At the same concentration, the IC50 value of ascorbic acid was 4.5 μg/mL. The synthesized compounds were also assessed for their in silico molecular docking analysis. Compounds 4 (−6.9 kcal/mol), 9 (−6.9 kcal/mol), and 10 (−7.9 kcal/mol) showed the maximum binding affinity close to ciprofloxacin (−7.2 kcal/mol) used as a positive control. Thus, compounds 4, 9, and 10 showed the best antibacterial activities in both in vitro and molecular docking analyses among the synthetic compounds. The results of in silico molecular docking evaluation of the synthetic compounds against E. coli DNA gyrase B were in good agreement with the in vitro antibacterial analysis. Therefore, the antibacterial activity displayed by these compounds is encouraging for further investigation to improve the activities of [2,3′-biquinoline]-4-carboxylic acid by incorporating various bioisosteric groups in either of the quinoline rings.

The antimicrobial potential and pharmacokinetic profiles of novel quinoline-based scaffolds: synthesis and in silico mechanistic studies as dual DNA gyrase and DHFR inhibitors

The resistance of pathogenic microbes to currently available antimicrobial agents has been considered a global alarming concern.

Recent update on antibacterial and antifungal activity of quinoline scaffolds

Although most of the heterocycles have been reported to possess a significant pharmacological activity, only a few of them, namely quinoline derivatives, have exhibited the finest biological activities. Despite the few medicinal properties of the plain quinoline molecule, its derivatives exhibit diverse pharmacological properties such as anticancer, anti-inflammatory, antibacterial, antiviral, antifungal, antiprotozoal activities, and so on. The potential antimicrobial properties of the quinoline derivatives are evident from the decades of research on these derivatives. Owing to limitations like drug resistance, high cost, severe side effects, and less bioavailability of previously synthesized antimicrobial agents, these drugs have become obsolete in recent years. Hence, the design of more efficient antimicrobial drugs must be given topmost priority. A breakthrough in drug discovery is a must to prevent malevolent microbial diseases. Addressing all these issues, researchers have been continuously contributing to antimicrobial drug discovery. Herein, a short description of the pharmacology of antimicrobial agents such as antibacterials and antifungals synthesized recently is provided. The versatile derivatization of the quinoline moiety leading to significant antimicrobial potencies is discussed, considering the structure-activity relationship.

Quinoline Based Monocarbonyl Curcumin Analogs as Potential Antifungal and Antioxidant Agents: Synthesis, Bioevaluation and Molecular Docking Study

In search for new fungicidal and free radical scavenging agents, we synthesized a focused library of 2-chloroquinoline based monocarbonyl analogs of curcumin (MACs). The synthesized MACs were evaluated for in vitro antifungal and antioxidant activity. The antifungal activity was evaluated against five different fungal strains such as Candida albicans, Fusarium oxysporum, Aspergillus flavus, Aspergillus niger, and Cryptococcus neoformans, respectively. Most of the synthesized MACs displayed promising antifungal activity compared to the standard drug Miconazole. Furthermore, molecular docking study on a crucial fungal enzyme sterol 14α-demethylase (CYP51) could provide insight into the plausible mechanism of antifungal activity. MACs were also screened for in vitro radical scavenging activity using butylated hydroxytoluene (BHT) as a standard. Almost all MACs exhibited better antioxidant activity compared to BHT.

Convenient synthesis of quinoline-fused triazolo-azepine/oxepine derivatives through Pd-catalyzed C–H functionalisation of triazoles

The convenient synthesis of a novel polycyclic fused system comprising three different heterocycles, viz., quinolines, azepines/oxepines and triazoles is presented in high yields.

Synthesis, crystal structure and Hirshfeld surface analysis of 2-chloro-3-[(E)-(2-phenyl-hydrazinyl-idene)meth-yl]quinoline

A new quinoline-based hydrazone, C16H12ClN3, was synthesized by a condensation reaction of 2-chloro-3-formyl-quinoline with phenyl-hydrazine. The quinoline ring system is essentially planar (r.m.s. deviation = 0.012 Å), and forms a dihedral angle of 8.46 (10)° with the phenyl ring. The mol-ecule adopts an E configuration with respect to the central C=N bond. In the crystal, mol-ecules are linked by a C-H⋯π-phenyl inter-action, forming zigzag chains propagating along the [10] direction. The N-H hydrogen atom does not participate in hydrogen bonding but is directed towards the phenyl ring of an adjacent mol-ecule, so linking the chains via weak N-H⋯π inter-actions to form of a three-dimensional structure. The Hirshfeld surface analysis of the crystal structure indicates that the most important contributions to the crystal packing are from H⋯H (35.5%), C⋯H/H⋯C (33.7%), Cl⋯H/H⋯Cl (12.3%), N⋯H/H⋯N (9.5%) contacts.

Synthesis, Structure, Chemical Stability, and In Vitro Cytotoxic Properties of Novel Quinoline-3-Carbaldehyde Hydrazones Bearing a 1,2,4-Triazole or Benzotriazole Moiety

A small library of novel quinoline-3-carbaldehyde hydrazones (Series 1), acylhydrazones (Series 2), and arylsulfonylhydrazones (Series 3) bearing either a 1,2,4-triazole or benzotriazole ring at position 2 was prepared, characterized by elemental analyses and IR, NMR, and MS spectra, and then subjected to in vitro cytotoxicity studies on three human tumor cell lines: DAN-G, LCLC-103H, and SISO. In general, compounds 4, 6, and 8 substituted with a 1,2,4-triazole ring proved to be inactive, whereas the benzotriazole-containing quinolines 5, 7, and 9 elicited pronounced cancer cell growth inhibitory effects with IC50 values in the range of 1.23⁻7.39 µM. The most potent 2-(1H-benzotriazol-1-yl)-3-[2-(pyridin-2-yl)hydrazonomethyl]quinoline (5e) showed a cytostatic effect on the cancer cell lines, whereas N′-[(2-(1H-benzotriazol-1-yl)quinolin-3-yl)methylene]-benzohydrazide (7a) and N′-[(2-1H-benzotriazol-1-yl)quinolin-3-yl)methylene]-naphthalene-2-sulfonohydrazide (9h) exhibited selective activity against the pancreas cancer DAN-G and cervical cancer SISO cell lines. Based on the determined IC50 values, the compound 5e seems to be leading compound for further development as anticancer agent.