Mannich bases of 3H-pyrrolo[3,2-f]quinoline having vasorelaxing activity

Gold catalysis in quinoline synthesis

Quinolines are biologically and pharmaceutically important N-heterocyclic aromatic compounds, which have broad applications in medicinal chemistry. Thus, their efficient synthesis has attracted extensive attention, and a broad range of synthetic strategies have been established. Of note, gold-catalyzed methodologies for the synthesis of quinolines have greatly advanced this field. Various gold-catalyzed intermolecular annulation reactions, such as annulations of aniline derivatives with carbonyl compounds or alkynes, annulations of anthranils with alkynes, and annulations based on A3-coupling reactions, as well as intramolecular cyclization reactions of azide-tethered alkynes, 1,2-diphenylethynes, and 2-ethynyl N-aryl indoles, have been developed. This review provides an overview of this exciting research area. Typical achievements in reaction methodologies and plausible reaction mechanisms are summarized.

Biological properties of pyrroloquinoline and pyrroloisoquinoline derivatives

In this review, we summarize pyrroloquinoline and pyrroloisoquinoline derivatives (PQs and PIQs) that act on a broad spectrum of biological targets and are used as bacteriostatic, antiviral, plasmodial, anticancer, antidiabetic and anticoagulant agents. Many of these compounds play important roles in the study of DNA and its interactions, the regulation of the cell cycle and programmed cell death. This review involves twenty-five types of skeletally analogical compounds bearing pyrrole and (iso)quinoline scaffolds with different mutual annelations.

Molecular Docking Study for Binding Affinity of 2H-thiopyrano[2,3-b]quinoline Derivatives against CB1a

Quinoline-based molecules are major constituents in natural products, active pharmacophores, and have excellent biological activities. Using 2H-thiopyrano[2,3-b]quinoline derivatives and CB1a protein (PDB ID: 2IGR), the molecular docking study has been revealed in this article. The study of in silico molecular docking analysis of such derivatives to determine the binding affinity, residual interaction, and hydrogen bonding of several 2H-thiopyrano[2,3-b]quinolines against CB1a is reported here. The current work demonstrated that 2H-thiopyrano[2,3-b]quinoline derivatives could be effective antitumor agents to produce potent anticancer medicines in the near future.

Synthesis and Evaluation of Novel S-alkyl Phthalimide- and S-benzyl-oxadiazole-quinoline Hybrids as Inhibitors of Monoamine Oxidase and Acetylcholinesterase

New S-alkyl phthalimide 5a-f and S-benzyl 6a-d analogs of 5-(2-phenylquinolin-4-yl)-1,3,4-oxadiazole-2-thiol (4) were prepared by reacting 4 with N-bromoalkylphthalimide and CF₃-substituted benzyl bromides in excellent yields. Spectroscopic techniques were employed to elucidate the structures of the synthesized molecules. The inhibition activity of newly synthesized molecules toward MAO-A, MAO-B, and AChE enzymes, was also assessed. All these compounds showed activity in the submicromolar range against all enzymes. Compounds 5a and 5f were found to be the most potent compounds against MAO-A (IC₅₀ = 0.91 ± 0.15 nM) and MAO-B (IC₅₀ = 0.84 ± 0.06 nM), while compound 5c showed the most efficient acetylcholinesterase inhibition (IC₅₀ = 1.02± 0.65 μM). Docking predictions disclosed the docking poses of the synthesized molecules with all enzymes and demonstrated the outstanding potency of compounds 5a, 5f, and 5c (docking scores = -11.6, -15.3, and -14.0 kcal/mol against MAO-A, MAO-B, and AChE, respectively). These newly synthesized analogs act as up-and-coming candidates for the creation of safer curative use against Alzheimer's illness.

Design, synthesis and biological evaluation of dehydroabietic acid derivative as potent vasodilatory agents

Using dehydroabietic acid as the lead compound for structural modification, 25 dehydroabietic acid derivatives were synthesized. Among them, compound D1 not only showed the strongest relaxation effect on the aortic vascular ring in vitro (Emax = 99.5 ± 2.1%, EC50 = 3.03 ± 0.96 µM), but also significantly reduced systolic and diastolic blood pressure in rats at a dose of 2.0 mg/kg in vivo. Next, the vascular protective effect of the best active D1 and its molecular mechanism were further investigated by HUVECs. The results showed that D1 induced endothelium-dependent diastole in the rat thoracic aorta in a concentration-dependent manner. Endothelium removal or aortic ring pretreatment with NG-nitro-l-arginine methylester (l-NAME), 1H-[1,2,4]-oxadiazolo-[4,3-a]-quinoxalin-1-one (ODQ), and tetraethylammonium (TEA) significantly inhibited D1-induced relaxation. In addition, wortmannin, KT5823, triciribine, diltiazem, BaCl2, 4-aminopyridine, indomethacin, propranolol, and atropine attenuated D1-induced vasorelaxation. D1 increased the phosphorylation of eNOS in HUVECs Furthermore, D1 attenuated the expression of TNF-α-induced cell adhesion molecules such as ICAM-1 and VCAM-1. However, this effect was attenuated by the eNOS inhibitors l-NAME and asymmetric dimethylarginine (ADMA). The findings suggest that D1-induced vasorelaxation through the PI3K/Akt/eNOS/NO/cGMP/PKG pathway by activating the KCa, Kir and KV channels or muscarinic and β-adrenergic receptors, and inhibiting the l-type Ca2+ channels, which is closely related to the hypotensive action of the agent. Furthermore, D1 exhibits an inhibitory effect on vascular inflammation, which is associated with the observed vascular protective effects.

Dopamine-Mediated Vanillin Multicomponent Derivative Synthesis via Grindstone Method: Application of Antioxidant, Anti-Tyrosinase, and Cytotoxic Activities

Purpose

This study aimed to determine the extent of contribution of dopamine to antioxidant and anti-tyrosinase activities, by dopamine addition to vanillin. This study achieved the synthesis of dopamine-associated vanillin Mannich base derivatives prepared via a one-step reaction involving a green chemistry approach, and investigation of antioxidant and anti-tyrosinase activities.

Methods

Novel one-pot synthesis of Mannich base dopamine-connected vanillin (1a-l) derivatives can be achieved via green chemistry without using a catalyst. Newly-prepared compounds were characterised with FTIR and NMR (¹H and ¹³C) spectra, mass spectra, and elemental analyses. In total, 12 compounds (1a-l) were synthesised and their antioxidant and anti-tyrosinase activities evaluated. Antioxidant activities of 2,2-diphenyl-1-picrylhydrazyl (DPPH), nitric oxide (NO), hydrogen peroxide (H₂O₂), and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), and diammonium assays, ABTS^•+ radical scavenging, and linoleic acid peroxidation were used to screen all synthesised compounds (1a-l) for anti-tyrosinase activities and cytotoxicity against MCF-7 and Vero cell lines;.

Results

The compound 1k inhibited (IC₅₀:11.02µg/mL) the DPPH-scavenging activity to a greater extent than the standard BHT (IC₅₀:25.17µg/mL), and showed high activity in H₂O₂ and NO scavenging assays. Compound 1e was more potent (96.21%) against ABTS and compound 1k was more potent (95.28%) against 2,2ʹ-azobis(2-amidinopropane)dihydrochloride antioxidant than the standard trolox. All synthesised compounds were screened for anti-tyrosinase inhibitory activity. Compound 1e had higher activity against tyrosinase (IC₅₀=10.63 µg/mL), than kojic acid (IC₅₀=21.52µg/mL), and was more cytotoxic (GI₅₀ 0.01µM) against MCF-7 cell line than the doxorubicin standard and other tested compounds.

Conclusion

In this study, all compounds were found to possess significant antioxidant and anti-tyrosinase activities. Compounds 1e and 1k performed well, compared with other compounds, in all assays. In addition, this study successfully identified several promising molecules that exhibited antioxidant and anti-tyrosinase activities.

Recent Progress in the Synthesis of Quinolines

BACKGROUND

Quinoline-containing compounds present in both natural and synthetic products are an important class of heterocyclic compounds. Many of the substituted quinolines have been used in various areas including medicine as drugs. Compounds with quinoline skeleton possess a wide range of bioactivities such as antimalarial, anti-bacterial, anthelmintic, anticonvulsant, antiviral, anti-inflammatory, and analgesic activity. Due to such a wide range of applicability, the synthesis of quinoline derivatives has attracted a lot of attention of chemists to develop effective methods. Many known methods have been expanded and improved. Furthermore, various new methods for quinoline synthesis have been established. This review will focus on considerable studies on the synthesis of quinolines date which back to 2014.

OBJECTIVE

In this review, we discussed recent achievements on the synthesis of quinoline compounds. Some classical methods have been modified and improved, while other new methods have been developed. A vast variety of catalysts were used for these transformations. In some studies, quinoline synthesis reaction mechanisms were also displayed.

CONCLUSION

Many methods for the synthesis of substituted quinoline rings have been developed recently. Over the past five years, the majority of those reported have been based on cycloisomerization and cyclization processes. Undoubtedly, more imaginative approaches to quinoline synthesis will appear in the literature in the near future. The application of known methods to natural product synthesis is probably the next challenge in the field.

Synthesis of Schiff and Mannich bases of news-triazole derivatives and their potential applications for removal of heavy metals from aqueous solution and as antimicrobial agents

An efficient synthesis of Schiff and Mannich bases of news-triazole derivatives under mild conditions has been developed for the removal of Pb²⁺, Cd²⁺, Ca²⁺, and Mg²⁺from aqueous solutions and as antimicrobial agents.

Crystal structure of benzo[h]quinoline-3-carbox-amide

The title com-pound, C14H10N2O, crystallizes in the monoclinic space group P21/c with four mol-ecules in the unit cell. All 17 non-H atoms of one mol-ecule lie essentially in one plane. In the unit cell, two pairs of mol-ecules are exactly coplanar, while the angle between these two orientations is close to perfectly perpendicular at 87.64 (6)°. In the crystal, mol-ecules adopt a 50:50 crisscross arrangement, which is held together by two nonclassical and two classical inter-molecular hydrogen bonds. The hydrogen-bonding network together with off-centre π-π stacking inter-actions between the pyridine and outermost benzene rings, stack the mol-ecules along the b-axis direction.

Efficient Synthesis of 1,9-Substituted Benzo[h][1,6]naphthyridin-2(1H)-ones and Evaluation of their Plasmodium falciparum Gametocytocidal Activities

A novel three-component, two-step, one-pot nucleophilic aromatic substitution (S_NAr)-intramolecular cyclization-Suzuki coupling reaction was developed for the synthesis of benzo[h][1,6]naphthyridin-2(1H)-ones (Torins). On the basis of the new efficiently convergent synthetic route, a library of Torin analogs was synthesized. The antimalarial activities of these compounds were evaluated against asexual parasites using a growth inhibition assay and gametocytes using a viability assay.

Vanillic Mannich bases: synthesis and screening of biological activity. Mechanistic insight into the reaction with 4-chloroaniline

Vanillic Mannich bases were catalytically synthesized, and their cytotoxic and antioxidative activities examined.

Synthesis and anticonvulsant activity of 1-(2-(8-(benzyloxy)quinolin-2-yl)-1-butyrylcyclopropyl)-3-substituted urea derivatives

In the present study on the development of new anticonvulsants, 16 new1-(2-(8-(benzyloxy)quinolin-2-yl)-1-butyrylcyclopropyl)-3-substituted urea derivatives were synthesized and tested for anticonvulsant activity using the maximal electroshock seizure, subcutaneous pentylenetetrazole screens, which are the most widely employed seizure models for early identification of candidate anticonvulsants. Their neurotoxicity was determined by applying the rotorod test. Three compounds 7a, 7e, and 7m showed promising anticonvulsant activities in both models employed for anticonvulsant evaluation. The most active compound 7e showed the maximal electroshock seizure-induced seizures with ED(50) value of 14.3 mg/kg and TD(50) value of 434 mg/kg after intraperitoneal injection to mice, which provided compound 7e with a protective index (TD(50) /ED(50) ) of 30.3 in the maximal electroshock seizure test.

Synthesis and anticonvulsant activity of 1-(8-(benzyloxy)quinolin-2-yl)-6-substituted-4,6-diazaspiro[2,4]heptane-5,7-diones

In the present study on the development of new anticonvulsants, 16 new1-(8-(benzyloxy)quinolin-2-yl-6-substituted-4,6-diazaspiro[2,4]heptane-5,7-diones were synthesized and tested for anticonvulsant activity using the maximal electroshock (MES), subcutaneous pentylenetetrazole (scPTZ) screens, which are the most widely employed seizure models for early identification of candidate anticonvulsants. Their neurotoxicity was determined applying the rotorod test. Two compounds 8e and 8j showed promising anticonvulsant activities in both models employed for anticonvulsant evaluation. The most active compound 8e showed the MES-induced seizures with ED(50) value of 8.6 mg/kg and TD(50) value of 365.3 mg/kg after intraperitoneally injection to mice, which provided compound 8e with a protective index (TD(50)/ED(50)) of 26.8 in the MES test.

1-(2-Benzoyl-1-phenyl-eth-yl)-4-[(2-hy-droxy-1-naphth-yl)methyl-idene-amino]-3-methyl-1H-1,2,4-triazole-5(4H)-thione

In the title compound, C(29)H(24)N(4)O(2)S, intra-molecular O-H⋯N hydrogen bonding influences the mol-ecular conform-ation; the naphthol system and triazole ring form a dihedral angle of 3.88 (7)°. In the crystal, π-π inter-actions between the five- and six-membered rings of neighbouring mol-ecules [centroid-centroid distances = 3.541 (3) and 3.711 (3) Å] consolidate the crystal packing.

3-{1-[4-(2-Methyl-prop-yl)phen-yl]eth-yl}-1-(morpholinometh-yl)-4-(4-nitro-benzyl-ideneamino)-1H-1,2,4-triazole-5(4H)-thione

The title ibuprofen-containing Mannich derivative, C(26)H(32)N(6)O(3)S, crystallizes with two independent mol-ecules in the asymmetric unit. The morpholine ring in each mol-ecule adopts a chair conformation. The 1,2,4-triazole ring forms dihedral angles of 2.13 (10) and 75.52 (10)° with the two substituted benzene rings in one mol-ecule, with corresponding values of 19.36 (11)° and 89.03 (10)° in the other. The nitro groups are twisted from the attached benzene ring in each mol-ecule. In the crystal packing, mol-ecules are linked into supra-molecular chains via weak C-H⋯O, C-H⋯N and C-H⋯S inter-actions, and C-H⋯π and N-O⋯π links also occur.

4-(4-Bromobenzylideneamino)-3-{1-[4-(2-methylpropyl)phenyl]ethyl}-1-(morpholinomethyl)-1H-1,2,4-triazole-5(4H)-thione

There are two mol­ecules (A and B) in the asymmetric unit of the title compound, C₂₆H₃₂BrN₅OS, with almost identical geometry. The morpholine ring adopts the usual chair conformation in both mol­ecules. The triazole ring forms dihedral angles of 4.84 (6) and 74.19 (6)°, respectively, with the bromo­phenyl and isobutylbenzene rings in mol­ecule A, and angles of 16.68 (7) and 87.29 (6)°, respectively, in mol­ecule B. Intra­molecular C—H⋯S hydrogen bonds generate S(5) and S(6) ring motifs in both independent mol­ecules. The crystal structure is stabilized by C—H⋯N, C—H⋯Br and C—H⋯O hydrogen-bonding inter­actions, together with C—H⋯π inter­actions.

Convenient one pot synthesis and antimicrobial evaluation of some new Mannich bases carrying 4-methylthiobenzyl moiety

Two new series of Mannich bases, namely, 1-(morpholino)methyl-3-(4-methylthiobenzyl)-4-(substituted arylidene)amino-1,2,4-triazol-5-thiones 3 and 1-(N-methylpiperazino)methyl-3-(4-methylthiobenzyl)-4-(substituted arylidene)amino-1,2,4-triazol-5-thiones 4 have been synthesized by a three-component Mannich reaction (MCR) involving 3-(4-methylthiobenzyl)-4-(substituted arylidene)amino-5-mercapto-1,2,4-triazoles 2, formaldehyde and morpholine/N-methylpiperazine. The newly synthesized compounds were well characterized by elemental analysis, IR, (1)H NMR and mass spectral studies. They were also screened for their antibacterial and antifungal activities against a variety of microorganisms and the results of such studies have been discussed in this article.

Synthesis and biological activity of Schiff and Mannich bases bearing 2,4-dichloro-5-fluorophenyl moiety

A series of 2,4-dichloro-5-fluorophenyl bearing Mannich base (4 and 5) was prepared from triazole Schiff bases (3) by aminomethylation with formaldehyde and secondary/substituted primary amines. All newly synthesized compounds were screened for their antimicrobial activity. Compounds 3c, 4c, 4e and 4f exhibited promising antibacterial and compounds 3c, 5c, 5e and 5f showed good antifungal activity.

Novel anellated pyrazoloquinolin-3-ones: synthesis and in vitro BZR activity

A series of pyrazolo[4,3-c]pyrrolo[3,2-f]quinolin-3-one derivatives 6, 7a-c, 8a,b, 9a,b and 10-12 were synthesized as modified pyrazoloquinolinone analogs (PQs) and evaluated for their ability to inhibit radioligand to central and peripheral benzodiazepine receptors (BZRs) and their effect on GABA(A) alpha1beta2gamma2L receptors expressed in Xenopus laevis oocytes. Multistep synthesis starting from 5-nitroindole, via the Gould-Jacobs reaction to the quinoline nucleus, yielded key intermediates 9-chloro-3H-pyrrolo[3,2-f]quinoline-8-carboxylates. The reaction of the latter with methyl-hydrazine and various phenyl-hydrazines furnished the final compounds. In order to confirm the expected tetracyclic 2-substituted-2H-pyrazolopyrroloquinolin-3-one structure, IR spectrophotometric, mono-1H and 13C and bi-dimensional spectrometric and HRMS analyses were carried out: all compounds were found to be 2-substituted 3-keto tautomers; compound 6 only differed because it turned out to be 1-methyl-2H-pyrazolo[4,3-c]pyrrolo[3,2-f]quinolin-3-olo. The results of this work are consistent with those previously reported for PQs: 7-9 show high potency in displacing specific [3H]flunitrazepam from its receptor site; no compound was active in inhibiting the binding of [3H]PK 11195. They all act as antagonists at central BZR.

Synthesis, Anticonvulsant and Antihypertensive Activities of 8-Substituted Quinoline Derivatives

A series of 8-substituted quinolines were synthesized and tested against seizures induced by maximal electro shock (MES), pentylenetetrazole (scMet) and antihypertensive activities. Neurologic deficit was evaluated by the rotarod test. Among the newly synthesized derivatives, several compounds with a 2-hydroxypropyloxyquinoline moiety displayed excellent anticonvulsant and antihypertensive activities. Compound 20 (8-(3'-(4''-phenylpiperazino)-2'-hydroxypropyloxy)quinoline) was potent in both series as an anticonvulsive agent. 13 (8-(3'-piperazino)-2'-hydroxypropyloxyquinoline) and 14 (8-(3'-imidazolo)-2'-hydroxypropyloxyquinoline) showed very good anticonvulsant activities in the propanol series of compound, whereas in the ethane series, 1 (8-(2'-piperazino-ethanoxy)quinoline) and 2 (8-(2'-imidazolo-ethanoxy)quinoline) were the most active as anticonvulsive agents. Compounds 20 (8-(3'-(4''-phenylpiperazino)-2'-hydroxypropyloxy)quinoline), 13 (8-(3'-piperazino)-2'-hydroxypropyloxyquinoline) and 19 (8-(3'-(4''-ethylpiperazino)-2'-hydroxypropyloxy)quinoline) have shown excellent antihypertensive activity. They have significantly antagonized the pressor response elicited by adrenaline. These pharmacological results suggest that their anticonvulsant and antihypertensive effects may be correlated to the presence of beta-blocking properties, and that those properties depend on the presence of aryloxypropanolamine.

Microwave assisted Leimgruber-Batcho reaction for the preparation of indoles, azaindoles and pyrroylquinolines

The development of enhanced conditions for Lewis acid catalysed Leimgruber-Batcho indole synthesis using microwave acceleration is described. This approach has permitted the preparation of a variety of heteroaromatic enamine intermediates in good yield and high purities. Subsequent catalytic hydrogenation reactions, under various conditions including the use of a solid-phase encapsulated catalyst, furnish the corresponding indole derivatives in good yields.