[1,2,4]Triazolo[4,3-a]quinoxaline: synthesis, antiviral, and antimicrobial activities

A series of novel [1,2,4]triazolo[4,3-a]quinoxaline derivatives and their isosteres, pyrimido-quinoxaline, were synthesized as potential antiviral and antimicrobial agents. The new compounds were synthesized via aromatic nucleophilic substitution of 4-chloro-8-methyl[1,2,4]triazolo[4,3-a]quinoxaline-1-amine with different amines and triazole-2-thiol. Some of the synthesized compounds were subjected to antiviral and cytotoxicity screening using plaque-reduction assay. Most of the tested compounds exhibited cytotoxicity at concentration 160?μg/ml and compound 8b showed promising antiviral activity. In vitro antimicrobial screening against different pathogenic organisms using agar diffusion method demonstrated that compounds 4d, 6c, 7b, and 8a exhibit antibacterial and/or antifungal activities.     

Antimicrobial and antiquorum-sensing studies. Part 2: synthesis, antimicrobial, antiquorum-sensing and cytotoxic activities of new series of fused [1,3,4]thiadiazole and [1,3]benzothiazole derivatives

New series of [1,3,4]thiadiazolo[3,2-a]pyrimidines, [1,3,4]thiadiazolo[2,3-b]quinazolines, and pyrimido[2,1-b][1,3]benzothiazoles have been synthesized and characterized by analytical and spectrometrical methods (IR, MS, ¹H, and ¹³C NMR). Sixteen of the synthesized compounds; namely, 3a, b, 5a–f, 8a, b, 10, 11a–c, and 13a, b were screened for antibacterial activity against Escherichia coli, Staphylococcus aureus, and Bacillus cereus. They were found to be either moderately active, slightly active or inactive against the selected microorganisms. The antifungal activity of these compounds were also tested against Candida albicans, Aspergillus fumigatus 293, and Aspergillus flavus 3375. Compound 11a showed potent antifungal activity against the three selected fungi; the rest of the tested compounds displayed either weaker activity or were completely inactive. The same compounds were examined for antiquorum-sensing activity against Chromobacterium violaceum ATCC 12472, where compounds 3a, 10, 11a, and 13a, b exhibited promising activity. The in vitro cytotoxic activity of these compounds was also studied by brine shrimp lethality bioassay, and results indicated that compounds 3a, 11a, and 13a have the highest cytotoxic activity.     

Synthesis of some new indolo[2,3-c]isoquinolinyl pyrazoles, -1,3,4-oxadiazoles and their biological activities

A new series of novel compounds [10-substituted 6H, 7H-indolo[2,3-c]isoquinolin-5-one-6-yl]carbohydrazides (3a–c), 1-[10-substituted 6H, 7H-indolo[2,3-c]isoquinolin-5-one-6-yl]fomyl-, -3′,5′-dimethylpyrazoles (4a–c), -3′,5′-diphenylpyrazoles (5a–c), -3′-methylpyrazol-5′-ones (6a–c) and -1′,3′,4′-oxidiazole-2′-thiones (7a–c) linked to indoloisoquinoline at position-6 through formyl bridge was prepared. The structures of these newly synthesized compounds were confirmed by their spectral studies and elemental analysis. These compounds have been screened for their antimicrobial and antioxidant activities. Compounds 4a, 4b, 5a, 5b, 5c, 6b, 7a, and 7c exhibited the maximum zone of inhibition against A. niger, A. flavus, and A. fumigatus. Compounds 4a, 5a, 5c, 6b, 6c, 7a, and 7b showed good antibacterial activity. Compounds 4b, 4c, 5b, 5c, 6a, 6b, 7a, 7b, and 7c showed good radical scavenging activity compared with standards.     

Synthesis, antitumor activity, and structure–activity relationship of some 4H-pyrano[3,2-h]quinoline and 7H-pyrimido[4′,5′:6,5]pyrano[3,2-h]quinoline derivatives

Several 4H-pyrano[3,2-h]quinoline (3a–d, 4a, 7a,b, 9a–c, 10a,b, 11a,b, and 13a–c) and 7H-pyrimido[4′,5′:6,5]pyrano[3,2-h]quinoline derivatives (8a–c) were obtained by treatment of 8-hydroxyquinoline (1a) and 8-hydroxy-2-methylquinoline (1b) with α-cyano-p-chloro/bromocinnamonitrile (2a,b) or 4H-pyrano[3,2-h]quinoline derivatives (3a,c,d) with different electrophilic reagents followed by nucleophilic reagents. Structures of these compounds were established on the basis of spectral data. The antitumor activity of the synthesized compounds was investigated in comparison with Vinblastine. Among them, compounds 3c,d, 4a, 8b, 9b,c, 11a,b, and 13a,c inhibited the growth of cancer cells compared to Vinblastine. The structure–activity relationships were discussed.     

Iodine catalyzed one-pot synthesis of chloro-substituted linear and angular indoloquinolines and in vitro antiproliferative activity study of different indoloquinolines

This article describes a facile one-pot synthesis of different chloro-substituted linear and angular indoloquinolines using iodine as a catalyst and in vitro antiproliferative activity of these chloro-substituted indoloquinolines (3e and 3f) and some indolo[2,3-b]quinolines (3a–d) against human hepatocellular carcinoma HepG2 and human breast carcinoma MCF-7 cells. Anti-proliferative assay against human hepatocellular carcinoma HepG2 and human breast carcinoma MCF-7 cells indicated methyl-substituted 6H-indolo[2,3-b]quinoline 3c to be the most active and the parent 6H-indolo[2,3-b]quinoline 3a to be the least active, while the other compounds including the different chloro derivatives exhibited only intermediate activity.     

Synthesis, characterization, and in vitro antimicrobial evaluation of new 5-chloro-8-bromo-3-aryl-1,2,4-triazolo[4,3-c]pyrimidines

A series of new 5-chloro-8-bromo-3-aryl-1,2,4-triazolo[4,3-c]pyrimidines (4a–j) have been accomplished in excellent yields by the oxidative cyclization of pyrimidinylhydrazines (3a–j) of various aryl aldehydes with one equivalents of iodobenzene diacetate in methanol. The chemical structures of the synthesized compounds were confirmed by elemental analyses, FT-IR, ¹H NMR, ¹³C NMR, and mass spectral studies. Ten new compounds (4a–j) were tested in vitro for their antimicrobial activity against clinically isolated strains. Variable and modest activities were observed against the investigated strains of bacteria and fungi. Compounds 4f, 4i, and 4j demonstrated good antimicrobial activity against all the tested microbial strains.     

Synthesis and antitumor screening of new series of pyrimido-[4,5-b]quinolines and [1,2,4]triazolo[2′,3′:3,4]pyrimido[6,5-b]quinolines

New series of pyrimido[4,5-b]quinolines and [1,2,4]triazolo[2′,3′:3,4]pyrimido[6,5-b]quinolines have been synthesized. Compounds 4a, 4e, 4f, 4h, 5b, 5d, 6a, 6d, 6e, 8c, 8d, 10c–e, 10h, 11a, 11b, and 12a were tested for in vitro antitumor activity against human breast carcinoma (MCF-7) cell line, where compound 8d was found to be the most active member with IC₅₀ value of 3.62 μM. The DNA-binding affinity for the same compounds showed that compounds 8d and 10d exhibited the highest affinity to DNA. The detailed synthesis, spectroscopic, and biological data are reported.     

In vitro and in silico biological studies of novel thiazolo[3,2-a]pyrimidine-6-carboxylate derivatives

In the present study, we report the synthesis, characterization of new series of thiazolo[3,2-a]pyrimidine-6-carboxylate derivatives 3a–f and 4a–f. The newly synthesized compounds were screened for in vitro antimicrobial and antiviral activities. The probable mode of action of these active compounds was determined through in silico docking study by docking the receptor methionyl-tRNA synthetase and human inosine-5′-monophosphate dehydrogenase (IMPDH) for antibacterial and antiviral activities, respectively. Among the compounds, 4c exhibited excellent in vitro antimicrobial activity against all tested strains with binding and docking energies ?35.6 and ?12.4 kcal/mol, respectively. The antiviral studies were carried out for the selected compounds in which 4a exhibited 73.69 and 54.42 % of inhibition of buffalopox and camelpox viruses, respectively. Furthermore, compound 4a showed minimum docking and binding energy along with the maximum hydrogen/hydrophobic interaction with IMPDH. The study contributes towards identification and screening of potential antimicrobial and antiviral agent’s against the pathogens.     

Synthesis and anti-tubercular evaluation of some novel pyrazolo[3,4-d]pyrimidine derivatives

A series of phenothiazine clubbed pyrazolo[3,4-d]pyrimidines have been synthesized by using the Biginelli multi-component cyclocondensation reaction and their ability to inhibit growth of Mycobacterium tuberculosis in vitro have been determined. The results show that compounds 4b, 4d, and 4f exhibited excellent anti-tubercular activity with percentage inhibition of 93, 91, and 96, respectively, at a minimum inhibitory concentration (MIC) of <6.25?μg/ml, whereas compounds 4a, 4c, 4e, 4g, and 4h exhibited moderate to good anti-tubercular activity with percentage inhibition of 75, 68, 74, 54, and 63, respectively at a MIC of >6.25?μg/ml.     

Synthesis and evaluation of analgesic, anti-inflammatory, and anticancer activities of new pyrazole-3(5)-carboxylic acid derivatives

In this article, we synthesized a series of novel 1-benzyl-5(3)-p-tolyl-1H-pyrazole-3(5)-carboxylic acid derivatives and characterized by IR, ¹H NMR, and mass spectroscopy. Compounds were evaluated for their in vivo analgesic and anti-inflammatory activity using the p-benzoquinone-induced writhing test and the carrageenan-induced paw edema model, respectively. Out of 14 compounds tested, 7a, 7c, 7e, 7f, 7i, 8a–b, and 8f–g exhibited potent analgesic and/or anti-inflammatory activity as compared to reference drugs aspirin and indomethacin. Anticancer activity of these compounds was assessed against five cancer cell lines with the MTT assay (HL-60, human promyelocytic leukemia cells; HeLa, human cervical cancer cells; Raji, human B lymphocyte cell line; MCF7, human breast adenocarcinoma cell line; MDA-MB-231, estrogen-independent human breast cancer cell line). Compounds 7a, 8a, and 8b with high anti-inflammatory activity, and also 7d and 7j with mild anti-inflammatory activity exhibited promising anticancer activity against some selected cell lines.     

New approaches for the synthesis of pyrazole, thiophene, thieno[2,3-b]pyridine, and thiazole derivatives together with their anti-tumor evaluations

The reaction of cyanoacetylhydrazine (1) with acetylchloride (2) gave the N-acyl derivative 3. The latter underwent ready cyclization in sodium ethoxide to give the pyrazole derivative 4 which was the key compound for the synthesis of thiophene, thieno[2,3-b]pyridine, and thiazole derivatives. The anti-tumor evaluations of the newly synthesized products against the three human tumor cell lines, namely, breast adenocarcinoma (MCF-7), non-small cell lung cancer (NCI-H460), and CNS cancer (SF-268), were studied. Some of these compounds were found to exhibit much higher inhibitory effects toward the three tumor cell lines than the reference doxorubicin. Molecular modeling of the four compounds 12c, 12f, 16a, and 16d, which showed the maximum inhibitory effect, were done.     

Synthesis and antimicrobial screening of novel series of imidazo-[1,2-a]pyridine derivatives

In an attempt to find new bio-active molecules, a series of mannich bases N,N-dimethyl-1-(7-methyl-2-(aryl)imidazo[1,2-a]pyridin-3-yl)methanamines 4a–l were synthesized by mannich reaction of 7-methyl-2-(aryl)imidazo-[1,2-a]pyridines 3a–l with paraformaldehyde and N,N-dimethyl amine. Compounds 3a–l were prepared from reaction between different substituted 2-bromo-1-(aryl)ethanones 2a–l and 4-methylpyridin-2-amine 1. Structures of these compounds were confirmed by IR, ¹H NMR, ¹³C NMR, and mass spectral data. Antimicrobial screening of title compounds 3a–l was examined against Gram-positive bacteria (Staphylococcus aureus, Streptococcus pyogenes), Gram-negative bacteria (Escherichia coli, Pseudomonas aeruginosa), and fungi (Candida albicans, Aspergillus niger, Aspergillus clavatus) using serial broth dilution method. Some derivatives bearing halogen group was found to be equipotent or more potent than commercial drugs, against most of the employed strains, as evident from the screening data.     

Synthesis, anti-microbial evaluation, and molecular modeling of new pyrazolo[3,4-d]pyrimidine derivatives

Synthesis of some new pyrazolo[3,4-d]pyrimidine derivatives using readily available starting materials are described. A one-pot multi component cyclocondensation reaction was used to prepare the novel 3-methyl-4-aryl-1-phenyl-1H-pyrazolo[3,4-d]pyrimidine-6-thiol which served as a new starting material for all new compounds in this research. The anti-microbial activities of the selective synthesized compounds have been evaluated. Some of the newly prepared compounds were found to have moderate to strong anti-microbial activity, e.g., compound 4a, 6a, and 8, in comparison to the reference drugs. Molecular modeling of the most three biologically active new compounds 4a, 6a, and 8 compared to the reference drugs tobramycin and fluconazole was carried out using Fieldalign 2.0 software.     

Synthesis of novel 2-alkyl-4-substituted-amino-pyrazolo[3,4-d]pyrimidines as new leads for anti-bacterial and anti-cancer activity

Treatment of 6-alkyl-1-phenyl-4-chloro-(1H)-pyrazolo[3,4-d]pyrimidines, with different amines afforded a series of compounds whose identity and purity were confirmed by spectral and analytical means. The compounds were tested for antibacterial activity against four organisms viz. Staphylococcus aureus (Gram positive), S. epidermidis (Gram positive), Bacillus subtilis (Gram positive), Escherichia coli (Gram negative) using amoxicillin as standard control. Compounds 4d, 6b, 6c have shown best antibacterial activity in the series. The antiproliferative activity was tested against human skin cancer cell line G361. The compounds 3d, 4d, 5b, 5d, 5e, 6c, 7a were found to be the best of the series and showed the activity at micromolar concentration.     

Design, synthesis, antimicrobial, anti-inflammatory, and analgesic activity of novel dihydrobenzo furo[3,2-e]isoxazolo[4,5-b]azepin-5(5aH)-ones

Novel series of dihydro benzofuro[3,2-e]isoxazolo[4,5-b]azepin-5(5aH)-ones 6 have been synthesized from 3,5-dimethyl-4-nitroisoxazole 1. Compound 1 on treatment with salicyl aldehydes afforded the corresponding nitrostyrylisoxazoles 3, which upon reaction with ethyl bromo acetate followed by cyclization with triethylamine furnished ethyl 2,3-dihydro-3-[(3-methyl-4-nitro-5-isoxazolyl)methyl]benzofuran-2-carboxylates 5. Reductive cyclization of compounds 5 was effected with SnCl₂–MeOH to give the title compounds 6. Compounds 4–6 were characterized by IR, ¹H NMR, ¹³C NMR and Mass spectral data. The title compounds 6a–g were evaluated for their antimicrobial, anti-inflammatory, LOX-5 inhibitory, and analgesic activity. Compounds 6b and 6c exhibited significant antimicrobial activity, potent anti-inflammatory and analgesic activities as that of standard drugs.     

Acute and chronic anti-inflammatory evaluation of imidazo[1,2-a]pyridine carboxylic acid derivatives and docking analysis

A docking analysis performed on four selected imidazo[1,2-a]pyridine carboxylic acid derivatives indicated the binding of these to enzymes COX-1 and COX-2 active pockets. An in vitro analysis showed that compound 3-amino imidazo[1,2-a]pyridine-2-carboxylic acid (5) preferentially inhibited COX-2. The compounds (10?mg/kg) were evaluated in relation to a potential acute and chronic anti-inflammatory activity. Compound (5) and imidazo[1,2-a]pyridine-2-carboxylic acid (2) inhibited the edema produced by carrageenan more efficiently than indomethacin. Chronic anti-inflammatory activity was found in derivative (5) and indomethacin-treated groups in the granuloma model, the compound (2) and nitro-acid (4) had only a fair activity. Compound (2), nitro-carboxylate (3), and (5) did not produce gastroduodenal damage.     

Synthesis and pharmacological evaluation of pyrazolopyrimidopyrimidine derivatives: anti-inflammatory agents with gastroprotective effect in rats

We report the synthesis of new anti-inflammatory 1,7-dihydropyrazolo[3′,4′:4,5]pyrimido[1,6-a]pyrimidine 5 from aminocyanopyrazole. All compounds were characterized by physical, chemical and spectral studies. Preliminary pharmacological evaluation of the resulting products showed that compounds 5a, b, f (50–100 mg/kg, i.p) are active anti-inflammatory agents in carrageenan-induced rat paw oedema assay, and their effects are comparable to that of acetylsalicylic–lysine (300 mg/kg, i.p.), used as a reference drug. The nature of substituent (Y, R₃) had a pronounced effect on the anti-inflammatory activity. Studies of structure–activity relationships have led to selection of compound ethyl-3,5-dimethyl-7-imino-N ¹-phenyl-1,7-dihydropyrazolo[3′,4′:4,5]pyrimido[1,6-a]pyrimidine-6-carboxylate, 5f which exhibited the most potent anti-inflammatory activity. In addition, the compounds 5a, b, f showed a significant gastroprotective effect against HCl/EtOH-induced gastric ulcer.     

Synthesis and antitumor activity of certain new thiazolo[2,3-b]quinazoline and thiazolo[3,2-a]pyrimidine analogs

A novel series of thiazolo[2,3-b]quinazoline (16–19, 25–28, and 34–37) and cyclohepta[d]thiazolo[3,2-a]pyrimidine (20–23, 29–32, and 38–41) analogs was designed and synthesized. Structure elucidation of the synthesized compounds was attained by the use of H¹ NMR, C¹³ NMR, and mass spectrometry. The obtained compounds were evaluated for their in vitro antitumor activity using the National Cancer Institute’s 60 cell lines’ panel assay that included nine tumor subpanels, namely, leukemia, non-small cell lung, colon, CNS, melanoma, ovarian, renal, prostate, and breast cancer cells. Most of the investigated compounds showed a remarkable broad-spectrum antitumor activity. Compounds 19, 28, 32, and 34 proved to be 10-, 15-, 2-, and 7-fold more active than 5-FU, with GI₅₀ MG-MID values of 2.4, 1.5, 11.2, and 3.1 μM, respectively.     

Synthesis and in vitro antitumor activity of new quinoline, pyrimido[4,5-b]quinoline, [1,2,3]triazino[4,5-b]quinoline, and [1,2,4]triazolo[2′,3′:3,4]pyrimido[6,5-b]quinoline analogs

New series of quinoline, pyrimido[4,5-b]quinoline, [1,2,3]triazino[4,5-b]quinoline, and [1,2,4]triazolo[2′,3′:3,4]pyrimido[6,5-b]quinoline analogs have been synthesized and characterized by analytical and spectrometrical methods (IR, ¹H NMR, ¹³C NMR, MS). Fifteen of the newly synthesized compounds; namely, 3a, b, 4b, 6a, b, 10a–f, and 14a–d were evaluated for their in vitro antitumor activity at the National Cancer Institute (NCI) 60 cell lines panel assay. Compounds 4b and 10f are the most active members in this study, demonstrating significant broad spectrum antitumor activity against most of the tested sub-panel tumor cell lines. The detailed synthesis, spectroscopic, and biological data are described.     

Synthesis, antitumor activity of 2-amino-4H-benzo[h]chromene derivatives, and structure–activity relationships of the 3- and 4-positions

Several 2-amino-4H-benzo[h]chromenes (3a–i) and (5a–h) were obtained by reaction of 4-chloro-1-naphthol (1) with α-cyanocinnamonitrile (2a–i) or ethyl α-cyanocinnamate derivatives (4a–h), respectively. Structures of these compounds were established on the basis of spectral data. The antitumor activity of the synthesized compounds was investigated in comparison with Vinblastine, Colchicine, and Doxorubicin well-known anticancer drugs, using MTT colorimetric assay. Among them, the compounds 5e, 3c, 5f, b, d, 3d, 5c, a were the most active against MCF-7, 5a against HCT-116 and 5a, 3e, a against HepG-2 as compared with the standard drug Vinblastine, while the compounds 5e, 3c, 5f, b, d, 3d, 5c, a, h, 3i, g, a, e were the most active against MCF-7, 5a, c, e, f, b, 3e, c, g, b, 5d, h, 3d, i, 5g against HCT-116, 5a, 3e, a, 5e, 3c, 5d, c, f, 3b, 5g, 3g, 5h against HepG-2 as compared with the standard drug Colchicine. The structure–activity relationships of the 3- and 4-positions were discussed.