Synthesis and antitumor activity of new sulfonamide derivatives of thiadiazolo[3,2-a]pyrimidines

New series of sulfonamide derivatives of [1,3,4]thiadiazolo[3,2-a]pyrimidine were synthesized and investigated as antitumor agents. Some of the newly prepared compounds were tested for their in vitro and in vivo antitumor activities. Preliminary biological studies revealed that compounds 4c, 4f, and 4j exhibited the highest affinity to DNA, while compounds 4h,i, 6a-c, 8 and 12-14 exhibited moderate activity. Also, compounds 4j, 4f and 4c showed the highest percentage increase in lifespan of mice inoculated with Ehrlich ascites cells over 5-flurouracil (positive control). The detailed synthesis, spectroscopic and biological data are reported.     

A regioselective synthesis of some new pyrazol-1'-ylpyrazolo[1,5-a]pyrimidines in aqueous medium and their evaluation as antimicrobial agents

An efficient and environmental benign regioselective synthesis of some new pyrazol-1′-ylpyrazolo[1,5-a]pyrimidines (7b-h) has been accomplished via treatment of 3(5)-amino-5(3)-hydrazinopyrazole dihydrochloride (5) with several unsymmetrical 1,3-diketones (6b-h) using water as a solvent without any catalysts or additives. The structure of 7b-h was established on the basis of rigorous analysis of ¹H, ¹³C NMR, IR spectral data and MS. Eight compounds (7a-h) were screened for their antibacterial activity against two gram-positive and two gram-negative bacteria and compounds (7a, b, d and e) for antifungal activity against four phytopathogenic fungi. Compounds 7c and 7e manifest rather broad antibacterial activity than standard antibiotics. One lead compound, 7a (10 mg/ml and 200 mg/ml) exhibited equipotent or more potent antifungal activity against all tested microorganisms than standard drug.     

Single step synthesis of new fused pyrimidine derivatives and their evaluation as potent Aurora-A kinase inhibitors

A simple, facile, efficient and one pot three-component procedure for the synthesis of pyrazolo[1,5-a]pyrimidines, triazolo[1,5-a]pyrimidines and pyrimido[1,2-a]benzimidazoles ring systems incorporating phenylsulfonyl moiety was developed via the reaction of 1-aryl-2-(phenylsulfonyl)ethanone derivatives 1a-d with the appropriate heterocyclic amine and triethyl orthoformate and evaluated as Aurora-A kinase inhibitors. The cytotoxic activity of the newly synthesized compounds against HST116 colon tumor cell line was investigated. 2,7-Diphenyl-6-(phenylsulfonyl)pyrazolo[1,5-a]pyrimidine (4b) and its p-methoxy analogue 4c were found to be equipotent to Doxorubicin as a reference drug. Molecular modeling study was carried out in order to rationalize the in vitro anti-tumor results.     

Synthesis and anticonvulsant activity of 8-alkoxy-5,6-dihydro-4H-[1,2,4]triazolo[4,3-a][1]benzazepin-1-one derivatives

A series of novel 8-alkoxy-5,6-dihydro-4H-[1,2,4]triazolo[4,3-a][1]benzazepin-1-one derivatives were synthesized and screened for their anticonvulsant activities by the maximal electroshock (MES) test, subcutaneous pentylenetetrazol (scPTZ) test, and their neurotoxicity was evaluated by the rotarod neurotoxicity test (Tox). The results of these tests demonstrated that 8-heptyloxy-5,6-dihydro-4H-[1,2,4]triazolo[4,3-a][1]benzazepin-1-one (3f) and 8-hexyloxy -5,6-dihydro-4H-[1,2,4]triazolo[4,3-a][1]benzazepin-1-one (3e) were the most promising compounds, with median effective dose (ED₅₀) of 17.6 and 17.9 mg/kg, and protective index (PI) of greater than 63.4 and 62.4 in the MES test, respectively. These PI values were higher than the PI value of the prototype antiepileptic drug carbamazepine. The scPTZ test showed that 8-pentyloxy-5,6-dihydro-4H-[1,2,4]triazolo[4,3-a][1]benzazepin-1-one (3d) was the most potent with ED₅₀ value of 38.0 mg/kg and PI value of greater than 29.4, which is much safer than marketed drug carbamazepine. The possible structure-activity relationship was discussed.     

Synthesis and antimicrobial activities of hexahydroimidazo[1,5-a]pyridinium bromides with varying benzyl substituents

Variously substituted benzyl bromides were employed to quaternize hexahydrobenzylimidazo[1,5-a]pyridine (A) and the resulting bromides (1-11) were evaluated for their in vitro antimicrobial activity against 10 pathogenic microorganisms: Staphylococcus aureus, Staphylococcus epidermidis, Bacillus cereus, Micrococcus luteus, Proteus vulgaris, Escherichia coli, Salmonella typhimurium, Klebsiella pneumonia, Candida albicans and Candida krusei. Antimicrobial activities were surprisingly high (MIC: 0.78-400 μg/mL) and the sensitivity of the salts tested has been found to depend strongly both on the benzyl substituents and the microorganisms used. However, the correlation observed between antimicrobial activity and calculated partition coefficient (ClogP) was poor. Acute toxicity assessment of these salts showed LD₅₀ of 757-2000 mg/kg, after oral administration in mice in 24 h.     

Synthesis of 4H-chromene, coumarin, 12H-chromeno[2,3-d]pyrimidine derivatives and some of their antimicrobial and cytotoxicity activities

Condensation of 3-N,N-diethylaminophenol (1) with α-cyanocinnamonitriles (2a-c) and ethyl α-cyanocinnamates (2d-f) provided compounds 3a-f and 4a-c. 12H-Chromeno[2,3-d]pyrimidine derivatives 6, 11-13 and 16 were obtained by treatment of 4H-chromene compounds (3) with different electrophiles followed by nucleophilic reagents. Structures of these compounds were established on the basis of IR, UV, ¹H NMR, ¹³C NMR and MS data. Some of the new compounds were evaluated for antimicrobial and cytotoxicity activities.     

Design and synthesis of 2-phenylimidazo[1,2-a]pyridines as a novel class of melatonin receptor ligands

A novel class of imidazo[1,2-a]pyridines as melatonin receptor ligands is designed and synthesized. The affinities of 3-(6-methoxy-2-phenylimidazo[1,2-a]pyridine-3-yl)-N-methyl-propionamide 8, N-[2-(6-methoxy-2-phenylimidazo[1,2-a]pyridine-3-yl)-ethyl]-acetamide 13 and N-(1-hydroxy-3-(5-methoxy-2-phenyl-1H-indol-3-yl)propan-2-yl)acetamide 18 are evaluated for binding on melatonin receptors. Compound 8 present good selectivity for MT₂ over MT₁ (MT₁/MT₂ = 19) and compound 13 have good affinities for both MT₁ (Ki :28 nM) and MT₂ (Ki : 8 nM).     

One-pot microwave assisted synthesis under green chemistry conditions, antioxidant screening, and cytotoxicity assessments of benzimidazole Schiff bases and pyrimido[1,2-a]benzimidazol-3(4H)-ones

The synthesis of a number of benzimidazole Schiff bases 3 and 3-oxo-pyrimido[1,2-a]benzimidazoles 4 in excellent yields by a one-step sequence from the reaction of 2-aminobenzimidazole under green chemistry conditions is described. Structural assignments of the new compounds as well as complete assignment of ¹H and ¹³C NMR signals have been unambiguously achieved based on the analysis of their ¹H and ¹³C NMR (1D and 2D), IR, MS and elemental analysis data. To the synthesized Schiff bases the E-configuration was assigned on the basis of comparison of experimental and calculated (DFT) ¹³C NMR chemical shifts. Compounds 3 and 4 were evaluated as inhibitors of lipoxygenase (LOX) and of lipid peroxidation (LPO). All the tested derivatives showed inhibition of lipid peroxidation, whereas most of them were found to have higher activation than the reference compound trolox; The Schiff bases 3e, 3h, and 3i, and the pyrimidobenzimidazoles 4a, 4e and 4f were found to be the most potent. The most potent LOX inhibitor within the subset of Schiff bases was found compound 3i, followed by 3f, whereas compounds 4a and 4g were found the most potent of the 3-oxo-pyrimido[1,2-a]benzimidazole group. Moreover, some cytotoxicity assessments were undertaken, whereupon it was found that Schiff base 3i and pyrimidobenzimidazoles 4e and 4f did not exhibit cytotoxicity at similar concentrations resembling thus the inhibitory activity of lipid peroxidation. The most cytotoxic Schiff base and pyrimidobenzimidazole were found to be 3d and 4c, respectively.     

Synthesis and anticancer evaluation of novel 2-cyclopropylimidazo[2,1-b][1,3,4]-thiadiazole derivatives

A series of 2,5,6-trisubstituted imidazo[2,1-b][1,3,4]-thiadiazole derivatives 4(a-k) have been prepared by reaction of 2-amino-5-cyclopropyl-1,3,4-thiadiazole and an appropriate phenacyl bromide. Further 5-bromo 5(a-k) and 5-thiocyanato 6(a-k) derivatives were synthesized in order to study the effect of these substituents on antitumor activity. Structures of these compounds were established by IR, ¹H NMR, ¹³C NMR and Mass spectroscopy. Seven compounds were granted NSC code at National Cancer Institute (NCI), USA for anticancer activity at a single high dose (10⁻⁵ M) in full NCI 60 cell panel. Among the compounds tested, 5-bromo-6-(4-chlorophenyl)-2-cyclopropylimidazo[2,1-b][1,3,4]thiadiazole 5b (NSC D-96022/1) was found to be the most active candidate of the series at five dose level screening with degree of selectivity toward Leukemic cancer cell line.     

Novel imidazo[4,5-b]pyridine and triaza-benzo[c]fluorene derivatives: synthesis, antiproliferative activity and DNA binding studies

In the present paper, we have described the synthesis and biological activity of the novel derivatives of imidazo[4,5-b]pyridines and triaza-benzo[c]fluorenes (7-21, 24-26, 28-29). A preponderance of these compounds exerted strong cytostatic effects on the panel of seven human tumour cell lines in a dose-dependent manner. In particular, imidazo[4,5-b]pyridines and triaza-benzo[c]fluorenes including 2-imidazolinyl derivatives showed the most potent antitumour activity. Similarly, triaza-benzo[c]fluorenes 18 and 20 induced strong growth inhibition of tested tumour cell lines, and showed low cytotoxicity in normal human fibroblasts. DNA interaction studies of these compounds demonstrated that N-methylated 16 and 2-imidazolinyl 28 triaza-benzo[c]fluorenes bind to DNA in an intercalative mode.     

Design, synthesis and in vitro antimicrobial evaluation of novel Imidazo[1,2-a]pyridine and imidazo[2,1-b][1,3]benzothiazole motifs

New antimicrobial agents, imidazo[1,2-a]pyridine and imidazo[2,1-b][1,3]benzothiazole, have been synthesized. Their antimicrobial activities were conducted against various Gram-positive, Gram-negative bacteria and fungi. Compounds 6c, 7a, 10b, 11a, 12b, 14a, 14b, 15a and 15b, exerted strong inhibition of the investigated bacterial and fungal strains compared to control antibiotics amoxicillin and cefixime and the antifungal agent fluconazole. Results from this study showed that the nature of the substituents on the armed aryl groups determines the extent of the activity of the fused imidazopyridine and/or imidazobenzothiazole derivatives. Preliminary structure-activity observations revealed that bromo-fluoro substituents enhanced the antimicrobial activity significantly compared to other substituents.     

Synthesis and identification of β-aryloxyquinolines and their pyrano[3,2-c]chromene derivatives as a new class of antimicrobial and antituberculosis agents

A new class of β-aryloxyquinolines 3a-i and their pyrano[3,2-c]chromene derivatives 6a-r incorporating a validated molecular target has been synthesized via a nucleophilic displacement and a one-pot multicomponent reaction respectively. In vitro antimicrobial activity of the synthesized compounds were investigated against a representative panel of pathogenic strains specifically Bacillus subtilis, Clostridium tetani, Streptococcus pneumoniae, Escherichia coli, Salmonella typhi, Vibrio cholera, Aspergillus fumigatus and Candida albicans. Compounds 3c, 3e, 3g, 6f, 6l and 6q exhibited excellent antibacterial activity while compound 6p exhibited more potent antifungal activity than that of first line standard drugs. In vitro antituberculosis activity was evaluated against Mycobacterium tuberculosis H37Rv and compound 6f is emerged as the promising antimicrobial member with better antitubercular activity. Majority of the compounds appears to be better antimicrobials but poor antituberculars.     

Synthesis and biological activity of 7H-benzo[4,5]indolo[2,3-b]-quinoxaline derivatives

New 7-(2-aminoethyl)-7H-benzo[4,5]indolo[2,3-b]quinoxalines (13-20) were synthesized with high yields starting from 3H-benzo[e]indole-1,2-dione. These compounds were screened for the cytotoxicity, anti-viral activity, interferon inducing ability and DNA affinity compared with the corresponding 6-(2-aminoethyl)-6H-indolo[2,3-b]quinoxaline derivatives (1-12). It was shown, that compounds 13-20 bind to DNA stronger (lg К_a = 6.23-6.87) than compounds 1-12 (lg К_a = 5.57-5.89). Anti-viral activity is significantly reduced with annulations of benzene ring in Indoloquinoxaline moiety 13-20.     

Design, synthesis, and antiproliferative activity of new 1H-pyrrolo[3,2-c]pyridine derivatives against melanoma cell lines

Synthesis of a new series of diarylureas and diarylamides having 1H-pyrrolo[3,2-c]pyridine scaffold is described. Their in vitro antiproliferative activity against A375P human melanoma cell line was tested and the effect of substituents on pyrrolo[3,2-c]pyridine nucleus was investigated. The newly synthesized compounds, except three N-tolyl derivatives (8f, 9f, and 9h), generally showed superior activity against A375P to Sorafenib. Among all of these derivatives, compounds 8b, 8g, and 9a-e showed the highest potency against A375P with IC₅₀ in nanomolar range. In addition, compounds 8d, 8e, 8h, 9g, 9i, and 9j were more potent than Sorafenib but with IC₅₀ in micromolar range. Compounds 8b, 8g, 9b-d, and 9i demonstrated higher selectivity towards A375P compared with NIH3T3 fibroblasts. The most potent diarylurea 8g and diarylamide 9d were further tested and showed high potency over nine melanoma cell lines at the NCI.     

Derivatives of pyrrolo[3,4-d]pyridazinone, a new class of analgesic agents

A series of N2-{2-[4-aryl(benzyl)-1-piperazinyl(piperidinyl)]ethyl}pyrrolo[3,4-d]pyridazinones 4 and related derivatives 5 were synthesized as potential analgesic agents. The structures of the new compounds were elucidated by micro, spectral and X-ray analysis. Analgesic activity of the compounds was investigated in the phenylbenzoquinone induced ‘writhing’ and ‘hot plate’ test in mice and at radioligand binding assay. At ‘writhing’ test all compounds, without exception, were more active than acetylsalicylic acid (ASA) with ED₅₀ values ranging from 0.04 to 11 mg/kg (i.p.) (ED₅₀ for ASA - 39.15 mg/kg). Analgesic effect at the ‘hot plate’ test was observed for three compounds 4c,e,f at the dose 3-5 times higher then that of morphine (ED₅₀-3.39 mg/kg). At radioligand binding assay of 4c,e,f only compound 4f exhibited affinity for the μ-opioid receptors similar to that of Tramadol. The acute toxicity of the pyrrolopyridazinones 4, 5 were also studied and non toxic effect was observed at the 2000 mg/kg (5a 1420 mg/kg) i.p. dose level. On the basis of the available pharmacological data S-A relationship is discussed. The preferred conformational characteristic of 4, taken 4c as an example, was also described.     

Synthesis and anticancer effects of some novel pyrazolo[3,4-d]pyrimidine derivatives by generating reactive oxygen species in human breast adenocarcinoma cells

A series of novel substituted pyrazolo[3,4-d]pyrimidines (compounds 2-12) were synthesized starting with pyrimidinone derivative 1. Their in vitro cytotoxicity against human breast adenocarcinoma (MCF-7) cell lines has been investigated and most of the tested compounds exploited potent cytotoxic activity against MCF-7 cell lines comparable to the activity of the commonly used anticancer drug cisplatin. Treatment of MCF-7 cells with increased doses (2, 5, 10, 20 μg/ml) of the tested compounds revealed that the activity of superoxide dismutase and the level of hydrogen peroxide were significantly increased, while the activities of catalase and glutathione peroxidase and the levels of reduced glutathione were significantly lowered compared with control MCF-7 cells. In general, acyclic nucleoside derivative 4 revealed the highest anticancer activity among the other tested compounds.     

Antifungal agents. Part 4: Synthesis and antifungal activities of novel indole[1,2-c]-1,2,4-benzotriazine derivatives against phytopathogenic fungi in vitro

A series of novel indole[1,2-c]-1,2,4-benzotriazine derivatives were obtained by a modified Sandmeyer reaction in the presence of tert-butylnitrite (t-BuONO). As compared with hymexazol, a commercially available agricultural fungicide, at the concentration of 50 μg/mL, two indole[1,2-c]-1,2,4-benzotriazines, 5h and 5k, exhibited the more promising and pronounced antifungal activities in vitro against five phytopathogenic fungi. It clearly demonstrated that introduction of appropriate substituents on the indolyl ring of indole[1,2-c]-1,2,4-benzotriazine (5a) would lead to the more potent derivatives.     

Synthesis and biological evaluation of novel Mannich bases of 2-arylimidazo[2,1-b]benzothiazoles as potential anti-cancer agents

A new series of Mannich bases of 2-arylimidazo[2,1-b]benzothiazoles were synthesized and evaluated for their anti-cancer activity. These compounds showed better cytotoxicity activity with IC₅₀ values ranging from 2.8 to 8.0 μM in HepG2, MCF-7 and HeLa cell lines. Further mechanism aspects responsible for the anti-cancer activity of two promising compounds 3c and 3f in HepG2 cell line were studied. Interestingly, 3c, 3f induced G2/M cell cycle arrest with down regulation of cyclin B and up regulation of Chk2 protein. Moreover, compounds 3c, 3f also showed the characteristic features of apoptosis such as enhancement in the levels of caspase-3. Treatments with compounds led to a decrease in levels of vital cell proliferation proteins such as Jun (C-Jun, JunB), p38 MAPK, p-JNK and PKCα. The compound 3f of the series could be considered as the potential lead for its development as a novel anti-cancer agent.     

Novel 4-aryl-pyrido[1,2-c]pyrimidines with dual SSRI and 5-HT(1A) activity. part 3

A number of 4-aryl-5,6,7,8-tetrahydropyrido[1,2-c]pyrimidine with 3-(1,2,3,6-tetrahydro-pyridin-4-yl)-1H-indole or 2-methyl-3-(1,2,3,6-tetrahydro-pyridin-4-yl)-1H-indole residues were synthesized for further investigation of SAR in a group of pyrido[1,2-c]pyrimidine derivatives with dual 5-HT_1A/SERT activity. Compounds 8a-8p were found to be potent ligands for both 5-HT_1A and SERT with K_i ranging from 28,3 to 642 nM and 42,4 nM-1,8 μM, respectively. Moreover compounds 8a, 8b, 8c, 8d, 8e and 8g were found to be selective agonists, while 8i as an antagonist of 5-HT_1A presynaptic receptors in the inducible hypothermia test in mice.     

Synthesis and antimycobacterial activity of prodrugs of indeno[2,1-c]quinoline derivatives

Recently we have reported anti-TB properties of a new class of conformationally-constrained indeno[2,1-c]quinolines, which are although considerably active (MIC 0.39-0.78 μg/mL) suffered from intense solubility problems. We thought of improving their bioavailability by prodrugs approach. Accordingly esters of the “Lead” indeno[2,1-c]quinolines 1, 15 and 27 derivatives were synthesized and their prodrug nature at the physiological pH were confirmed. Prodrugs were evaluated for their antimycobacterial activity against Mycobacterium tuberculosis H37Rv by MABA assay to show that they have 2- to 4-fold improved anti-TB activities, increased aqueous solubility and superior selectivity index over their respective parent compounds. MIC of these prodrugs was in the range of <0.20-6.0 μg/mL, and in general, no cytotoxicity was observed in VERO cells.