Benzoquinoline Derivatives: An Attractive Approach to Newly Small Molecules with Anticancer Activity.

This study presents the synthesis, structural characterization, and in vitro evaluation of anticancer activity of some newly benzo[f]quinoline derivatives. The synthesis is facile and efficient, involving two steps: quaternization of nitrogen heterocycle followed by a [3+2] dipolar cycloaddition reaction. The synthesized compounds were characterized by FTIR, NMR, and X-ray diffraction on monocrystal in the case of compounds 6c and 7c. An in vitro single-dose anticancer assay of eighteen benzo[f]quinoline compounds, quaternary salts, and cycloadducts, was performed. The results showed that the most active compounds were quaternary salts 3d and 3f with aromatic R substituents. Quaternary salt 3d revealed non-selective activity against all types of cancer cells, while salt 3f exhibited a highly selective activity against leukemia cells. Compound 3d also presented remarkable cytotoxic efficiency against four distinct types of cancer cells-namely, non-small cell lung cancer HOP-92, melanoma LOX IMVI, melanoma SK-MEL-5, and breast cancer MDA-MB-468. Compound 3f was selected for five-dose screening. The study also includes SAR correlations.

Benzoquinoline Chemical Space: A Helpful Approach in Antibacterial and Anticancer Drug Design.

Benzoquinolines are used in many drug design projects as starting molecules subject to derivatization. This computational study aims to characterize e benzoquinone drug space to ease future drug design processes based on these molecules. The drug space is composed of all benzoquinones, which are active on topoisomerase II and ATP synthase. Topological, chemical, and bioactivity spaces are explored using computational methodologies based on virtual screening and scaffold hopping and molecular docking, respectively. Topological space is a geometrical space in which the elements composing it can be defined as a set of neighbors (which satisfy a particular axiom). In such space, a chemical space can be defined as the property space spanned by all possible molecules and chemical compounds adhering to a given set of construction principles and boundary conditions. In this chemical space, the potentially pharmacologically active molecules form the bioactivity space. Results show a poly-morphological chemical space that suggests distinct characteristics. The chemical space is correlated with properties such as steric energy, the number of hydrogen bonds, the presence of halogen atoms, and membrane permeability-related properties. Lastly, novel chemical compounds (such as oxadiazole methybenzamide and floro methylcyclohexane diene) with drug-like potential, active on TOPO II and ATP synthase have been identified.

Novel Design of Neuropeptide-Based Drugs with ß-Sheet Breaking Potential in Amyloid-Beta Cascade: Molecular and Structural Deciphers.

Our work discusses the investigation of 75 peptide-based drugs with the potential ability to break the ß-sheet structures of amyloid-beta peptides from senile plaques. Hence, this study offers a unique insight into the design of neuropeptide-based drugs with ß-sheet breaker potential in the amyloid-beta cascade for Alzheimer's disease (AD). We started with five peptides (15QKLVFF20, 16KLVFF20, 17LVFF20, 16KLVF19 and 15QKLV18), to which 14 different organic acids were attached at the N-terminal. It was necessary to evaluate the physiochemical features of these sequences due to the biological correlation with our proposal. Hence, the preliminary analysis of different pharmacological features provided the necessary data to select the peptides with the best biocompatibility for administration purposes. Our approaches demonstrated that the peptides 17LVFF20, NA-17LVFF20, 16KLVF19 and NA-16KLVF19 (NA-nicotinic acid) have the ability to interfere with fibril formation and hence improve the neuro and cognitive functions. Moreover, the peptide conjugate NA-16KLVF19 possesses attractive pharmacological properties, demonstrated by in silico and in vitro studies. Tandem mass spectrometry showed no fragmentation for the spectra of 16KLVF19. Such important results suggest that under the action of protease, the peptide cleavage does not occur at all. Additionally, circular dichroism confirmed docking simulations and showed that NA-16KLVF19 may improve the ß-sheet breaker mechanism, and thus the entanglement process of amyloid-beta peptides can be more effective.

[3 + n] Cycloaddition Reactions: A Milestone Approach for Elaborating Pyridazine of Potential Interest in Medicinal Chemistry and Optoelectronics.

During the last few decades, pyridazine derivatives have emerged as privileged structures in heterocyclic chemistry, both because of their excellent chemistry and because of their potential applications in medicinal chemistry and optoelectronics. This review is focused on the recent advances in [3 + n] cycloaddition reactions in the pyridazine series as well as their medicinal chemistry and optoelectronic applications over the last ten years. The stereochemistry and regiochemistry of the cycloaddition reactions are discussed. Applications in optoelectronics (in particular, as fluorescent materials and sensors) and medicinal chemistry (in particular, antimicrobials and anticancer) are also reviewed.

Huisgen [3 + 2] Dipolar Cycloadditions of Phthalazinium Ylides to Activated Symmetric and Non-Symmetric Alkynes.

We present herein a straightforward and efficient pathway for the synthesis of pyrrolophthalazine cycloadducts via Huisgen [3 + 2] dipolar cycloaddition reactions of phthalazinium ylides to methyl propiolate or dimethyl acetylenedicarboxylate (DMAD). A thoroughly comparative study concerning the efficiency of synthesis, conventional thermal heating (TH) versus microwave (MW) and ultrasound (US) irradiation, has been performed. The cycloaddition reactions of phthalazinium ylides to methyl propiolate occur regiospecific, with a single regioisomer being obtained. Under conventional TH, the cycloaddition reaction of phthalazinium ylides with DMAD occurs to a mixture of inseparable partial and fully aromatized pyrrolophthalazine cycloadducts, while MW or US irradiation are leading only to fully aromatized compounds, with the reactions becoming selective. A feasible mechanism for formation of fully aromatized compounds is presented. Besides selectivity, it has to be noticed that the reaction setup under MW or US irradiation offer a number of other certain advantages: higher yields, decreasing of the amount of used solvent comparative with TH, decreasing of the reaction time from hours to minutes and decreasing of the consumed energy; consequently, these reactions could be considered environmentally friendly.

Microwave Assisted Reactions of Azaheterocycles Formedicinal Chemistry Applications.

Microwave (MW) assisted reactions have became a powerful tool in azaheterocycles chemistry during the last decades. Five and six membered ring azaheterocycles are privileged scaffolds in modern medicinal chemistry possessing a large variety of biological activity. This review is focused on the recent relevant advances in the MW assisted reactions applied to azaheterocyclic derivatives and their medicinal chemistry applications from the last five years. The review is divided according to the main series of azaheterocycles, more precisely 5- and 6-membered ring azaheterocycles (with one, two, and more heteroatoms) and their fused analogues. In each case, the reaction pathways, the advantages of using MW, and considerations concerning biological activity of the obtained products were briefly presented.

Hybrid Quinoline-Sulfonamide Complexes (M2+) Derivatives with Antimicrobial Activity.

Two new series of hybrid quinoline-sulfonamide complexes (M2+: Zn2+, Cu2+, Co2+ and Cd2+) derivatives (QSC) were designed, synthesized and tested for their antimicrobial activity. The synthesis is straightforward and efficient, involving two steps: acylation of aminoquinoline followed by complexation with metal acetate (Cu2+, Co2+ and Cd2+) or chloride (Zn2+). The synthesized QSC compounds were characterized by FTIR and NMR spectroscopy and by X-ray diffraction on single crystal. The QSC compounds were preliminary screened for their antibacterial and antifungal activity and the obtained results are very promising. In this respect, the hybrid N-(quinolin-8-yl)-4-chloro-benzenesulfonamide cadmium (II), considered as leading structure for further studies, has an excellent antibacterial activity against Staphylococcus aureus ATCC25923 (with a diameters of inhibition zones of 21 mm and a minimum inhibitory concentration (MIC) of 19.04 × 10-5 mg/mL), a very good antibacterial activity against Escherichia coli ATCC25922 (with a diameters of inhibition zones of 19 mm and a MIC of 609 × 10-5 mg/mL), and again an excellent antifungal activity against Candida albicans ATCC10231 (with a diameters of inhibition zones of 25 mm and a MIC of 19.04 × 10-5 mg/mL).

Synthesis, molecular modelling and anticancer evaluation of new pyrrolo[1,2-b]pyridazine and pyrrolo[2,1-a]phthalazine derivatives.

Two new series of heterocyclic derivatives with potential anticancer activity, in which a pyrrolo[1,2-b]pyridazine or a pyrrolo[2,1-a]phthalazine moiety was introduced in place of the 3'-hydroxy-4'-methoxyphenyl ring of phenstatin have been synthesised and their structure-activity relationship (SAR) was studied. Fourteen of the new compounds were evaluated for their in vitro cytotoxic activity by National Cancer Institute (NCI) against 60 human tumour cell lines panel. The best five compounds in terms of in vitro growth inhibition were screened in the second stage five dose-response studies, three of them showing a very good antiproliferative activity with GI50<100 nM on several cell lines including colon, ovarian, renal, prostate, brain and breast cancer, melanoma and leukemia. Docking experiments on the biologically active compounds showed a good compatibility with the colchicine binding site of tubulin.

Microwave Assisted Reactions of Fluorescent Pyrrolodiazine Building Blocks.

We report here the synthesis and optical spectral properties of several new pyrrolodiazine derivatives. The luminescent heterocycles were synthesized by 1,3-dipolar cycloaddition reactions between N-alkylated pyridazine and methylpropiolate or dimethyl acetylenedicarboxylate (DMAD). The pyrrolopyridazine derivatives are blue emitters with moderate quantum yields (around 25%) in the case of pyrrolopyridazines and negligible yet measurable emission for pyrrolophthalazines. In a subsequent step towards including the pyrrolodiazine moiety, given its spectral properties in various macromolecular frameworks such as biological molecules, a subset of the synthetized compounds has been subjected to α-bromination. A selective and efficient way for α-bromination in heterogeneous catalysis of pyrrolodiazine derivatives under microwave (MW) irradiation is presented. We report substantially higher yields under MW irradiation, whereas the solvent amounts required are at least five-fold less compared to classical heating.

New insides into chimeric and hybrid azines derivatives with antifungal activity.

During the last decades, five or six member rings azaheterocycles compounds appear to be an extremely valuable source of antifungal agents. Their use seems to be a very attractive solution in antifungal therapy and to overcome antifungal resistance in agriculture. The present review highlights the main results obtained in the field of hybrid and chimeric azine (especially pyridine, quinoline, phenanthroline, bypyridine, naphthyridine and their fused derivatives) derivatives presented in scientific literature from the last 10 years, with emphasis on antifungal activity of the mentioned compounds. A special attention was played to hybrid and chimeric azole-azine class, having in view the high antifungal potential of azoles.

[Box: see text].

Ultrasound assisted synthesis of hybrid quinoline anchored with 4-R-benzenesulfonamide moiety with potential antimicrobial activity.

We present in this paper a direct and efficient study regarding synthesis and spectral characterization of three series of hybrid quinoline anchored with 4-R-benzenesulfonamide moiety, with potential antimicrobial activity, by using ultrasound (US) irradiation and conventional methods (CV). The synthesis pathway is efficient and direct, in two steps: an initial N-acylation of 8-aminoquinoline followed by metal complexation with variously M2+ metals (Cd2+, Co2+, Cu2+, Ni2+, Pd2+, Zn2+). For both type of reactions, N-acylation and complexation, under US irradiations the synthesis have some undeniable advantages: the most relevant being the higher yields, a dramatically decrease for reaction time (with about 150 (one hundred fifty) folds for complexation) comparative with conventional methods (CV) (therefore the spent energy decrease in the same way), a decrease of the amount of used solvents. Taking into account the above considerations these reactions setup could be appreciated as eco-friendly. The structures of the obtained hybrid quinoline - sulfonamide complexes (HQBSM) were determined by elemental analysis and by using spectral investigations: FT-IR, NMR experiments, and X-ray diffraction (in three cases). The FT-IR and NMR spectra of complexes show a similar spectroscopic pattern for all complexes and fully confirm the proposed structures. The X-ray spectra analyses prove without doubts the structure of metal complexes, indicating that their structure depends essentially by two factors: the nature of metal and the nature of sulfonamide-quinoline moieties. Complexes containing 4-methoxy-benzoyl moiety and Zn2+ (e.g. 6a) are tetra-coordinated while in the Ni2+ complex (e.g. 6e) the metallic ion forms a distorted square-based bi-pyramid. In the complexes containing 4-nitro-benzoyl moiety and Cd2+ (e.g. 5d) the metallic ion forms a triangular bipyramid. The antibacterial and antifungal assay reveal that only hybrid HQBSM complex (4e) (with 4-chlorophenyl moiety and Ni2+ in molecule) have a significant antibacterial activity.

Hybrid Azine Derivatives: A Useful Approach for Antimicrobial Therapy.

Nowadays, infectious diseases caused by microorganisms are a major threat to human health, mostly because of drug resistance, multi-drug resistance and extensive-drug-resistance phenomena to microbial pathogens. During the last few years, obtaining hybrid azaheterocyclic drugs represents a powerful and attractive approach in modern antimicrobial therapy with very promising results including overcoming microbial drug resistance. The emphasis of this review is to notify the scientific community about the latest recent advances from the last five years in the field of hybrid azine derivatives with antimicrobial activity. The review is divided according to the main series of six-member ring azaheterocycles with one nitrogen atom and their fused analogs. In each case, the main essential data concerning synthesis and antimicrobial activity are presented.

Quinoline-imidazole/benzimidazole derivatives as dual-/multi-targeting hybrids inhibitors with anticancer and antimicrobial activity.

Two new classes of hybrid quinoline-imidazole/benzimidazole derivatives (the hybrid QIBS salts and QIBC cycloadducts) were designed and synthesized to evaluate their anticancer and antimicrobial activity. The strategy adopted for synthesis is straight and efficient, in four steps: N-acylation, N-alkylation, quaternization and a Huisgen 3 + 2 cycloaddition. The in vitro single-dose anticancer assay of forty six hybrid quinoline-benzimidazole compounds reveal that one QIBS salt (11h), has an excellent quasi nonselective activity against all type of cancer cell with an excellent PGI in the area of 90-100% and very good lethality. Three others quinoline-imidazole/benzimidazole hybrids (8h, 12h, 12f) has an excellent selective activity against some cancer cell lines: breast cancer MDA-MB-468 and Leukemia HL-60 TB). The five-dose assay screening confirms that compound 11h possesses excellent anti-proliferative activity, with GI50 in the range of nano-molar, against some cancer cell lines: Leukemia HL-60 TB, Leukemia K-526, Leukemia RPMI-8226, Breast cancer MDA-MB-468, Lung cancer HOP-92 and Ovarian cancer IGROV1. The antibacterial assay indicates that three hybrid QIBS salts (12f, 12c, 12d) have an excellent activity against Gram-negative bacteria E. coli (superior to control Gentamicin) while against Gram-positive bacteria S. aureus only one compound 8i (R2 = -CF3) exhibits a significant activity (superior to control Gentamicin). The MIC assay indicates that two other compounds (11h, 12h) are biologically active to a very low concentration, in the range of nano-molar. We believe that all these excellent assets related to anticancer and antibacterial activities, make from our hybrid quinoline-imidazole/benzimidazole compounds bearing a phenyl group (R2 = -C6H5) in the para (4)-position of the benzoyl moiety a good candidate for future drug developing.

Ultrasound assisted synthesis of hybrid quinoline-imidazole derivatives: a green synthetic approach.

A green, straightforward and efficient study for obtaining hybrid quinoline-imidazole derivatives under ultrasound (US) irradiation as well as under conventional thermal heating (TH) has been presented. The reaction pathway involves only two steps: the N-alkylation of imidazole ring and a Huisgen [3 + 2] dipolar cycloaddition reaction of ylides to dimethyl acetylenedicarboxylate (DMAD). For both types of reactions, a green workup procedure under US irradiation has been presented. Under US irradiation, the N-alkylation of nitrogen atoms from the imidazole nucleus has outstanding benefits in terms of reaction time, energy consumption and yields, and can thereby be considered an environmentally friendly method. Forty new hybrid quinoline-imidazole compounds have been synthesized: 18 salts, 8 dihydro-benzopyrrolo imidazolo quinoline, 9 benzopyrrolo-imidazolo quinoline and 5 dihydro-pyrroloquinoxaline quinoline cycloadducts.

Benzoquinoline Derivatives: A Straightforward and Efficient Route to Antibacterial and Antifungal Agents.

We report here the design, synthesis, experimental and in silico evaluation of the antibacterial and antifungal activity of some new benzo[f]quinoline derivatives. Two classes of benzo[f]quinolinium derivatives-(benzo[f]quinolinium salts (BQS) and pyrrolobenzo[f]quinolinium cycloadducts (PBQC)-were designed and obtained in two steps via a direct and facile procedure: quaternization followed by a cycloaddition reaction. The synthesized compounds were characterized by elemental and spectral analysis (FT-IR, 1H-NMR, 13C-NMR). The antimicrobial assay reveals that the BQS salts have an excellent quasi-nonselective antifungal activity against the fungus Candida albicans (some of them higher that the control drug nystatin) and very good antibacterial activity against the Gram positive bacterium Staphylococcus aureus. The PBQC compounds are inactive. Analysis of the biological data reveals interesting SAR correlations in the benzo[f]quinolinium series of compounds. The in silico studies furnished important data concerning the pharmacodynamics, pharmacokinetics and ADMET parameters of the BQS salts. Studies of the interaction of each BQS salt 3a-o with ATP synthase in the formed complex, reveal that salts 3j, 3i, and 3n have the best fit in a complex with ATP synthase. Study of the interaction of each BQS salt 3a-o with TOPO II in the formed complex reveals that salts 3j and 3n have the best-fit in complex with TOPO II. The in silico ADMET studies reveal that the BQS salts have excellent drug-like properties, including a low toxicity profile. Overall, the experimental and in silico studies indicate that compounds 3e and 3f (from the aliphatic series), respectively, and 3i, 3j and 3n (from the aromatic series), are promising leading drug candidates.

Bis-(imidazole/benzimidazole)-pyridine derivatives: synthesis, structure and antimycobacterial activity.

Aim: Over the last decades, few significant achievements have been made in tuberculosis (TB) therapy. As a result, there is an urgent need for new anti-TB drugs. Results: Two new classes of bis-(imidazole/benzimidazole)-pyridine derivatives were designed, synthesized and evaluated for their antimycobacterial activity. Conclusion: The synthesis is efficient and straightforward, involving only two successive N-alkylations. The anti-TB assay reveal that our compounds have an excellent anti-TB activity against both replicating and nonreplicating Mtb, are not cytotoxic, exhibited a very good intracellular activity and are active against drug-resistant Mtb strains, some compounds have a bactericidal mechanism. The absorption, distribution, metabolism, excretion and toxicity studies performed for one compound are promising, indicating that it is a good candidate for a future drug.