Synthesis of pyrazolo [4,3-c] pyridazine and isoxazolo [3,4-d] pyridazine derivatives

Arylhydrazones of diethyl acetonedicarboxylate3 was treated with formaldehyde to give 1-aryl-1,4,5,6-tetrahyeheypyridazine derivatives4a-f Cyclization of compound4a-f by hydroxylamine afforded [3,4-d] 1,4,5,6-tetrahydropyridazine derivatives5a-f. Also cyclization of compound4c with semicarbazide gave pyrazolote [4,3-c] pyridazine6. On the other hand compound 3 reacted with ethylorthoformate to give diethyl-1,4-dihydro-1-arylpyridazine-4-one-3,5 dicarboxylate7, which on treatment with hydrazine, semicarbazide and thiosemicarbzide gave pyridazine, amido and thioamido derivatives. The spectral and antimicrobial data of these compounds1–8 were studied.     

Synthesis and biological evaluation of some novel urea and thiourea derivatives of isoxazolo[4,5-d]pyridazine and structurally related thiazolo[4,5-d]pyridazine as antimicrobial agents

This study reports the synthesis of some novel isoxazolo[4,5-d]pyridazines and structurally related thiazolo[4,5-d]pyridazines, and their biological evaluation as antimicrobial agents. The proposed compounds were designed to contain pharmacophores such as urea, thiourea, sulfonylurea (thiourea) and some derived functionalities that are believed to contribute to the anticipated biological activities. The results revealed that 25 compounds displayed broad spectrum of antibacterial activity, with greater inhibitory effect on the growth of the tested Gram positive strains compared to Gram negative ones. Moreover, 14 compounds were able to produce appreciable growth inhibitory activity against Candida albicans fungus when compared to Clotrimazole. Most of the tested isoxazolo[4,5-d]pyridazines displayed better antimicrobial profile than their corresponding thiazolo[4,5-d]pyridazine congeners. Four compounds namely, p-(3,7-dimethyl-4-oxo-4H-isoxazolo [4,5-d]pyridazine-5-yl)benzenesulfonylthioureas (11c–d), 3-substituted-2-[p-(3,7-dimethyl-4-oxo-4H-isoxazolo[4,5-d]pyridazine-5-yl)-benzene-sufonylimino]-4-oxothiazolidines (13d) and p-(2,7-dimethyl-4-oxo-4H-thiazolo[4,5-d]pyridazin-5-yl)benzenesulfonylthiourea (24c) were found to be most active antimicrobial members in present study.     

2-Substituted-8-methyl-3,6-dihydroimidazo[4,5-c]pyrazolo[3,4-e]pyridazine as an anti-inflammatory agent

A series of 8-methyl-2-substituted-3,6-dihydroimidazo[4,5-c]pyrazolo[3,4-e]pyridazine compounds have been synthesized in the present investigation utilizing Philips condensation (Philips, J Chem Soc 2393?C2399, 1928). The anti-inflammatory activity of the synthesized compounds was evaluated using a carrageenin rat model.     

Synthesis and antitumor properties of pyrazolo [3,4-D] pyrimidine derivatives

Several new 5-substituted 1-phenylpyrazole [3,4-d] pyrimidine derivatives were synthesized and tested for antitumor activity. Compound 17, which has 3,4-dichlorophenyl moiety at N5 of the pyrazole pyrimidine ring, shows a strong activity against L-1210 leukemia (152%). On the other hand, compounds 15, 17 and 21 were the most active against sarcoma Sa-180. It was observed that many derivatives of pyrazole [3,4-d] pyrimidine possess different biological, especially antitumor properties [1-6, 9, 10].     

Synthesis and antimicrobial activity of novel pyrazolo[3,4-b]quinoline derivatives

New pyrazolo[3,4-b]quinoline derivatives have been prepared by cyclization of the intermediate 2-chloroquinoline-3-carbonitrile 7, namely 3-amino-1H-pyrazolo[3,4-b]quinoline 8a, 3-amino-1-phenyl/(p-substituted)phenyl/-1H-pyrazolo[3,4-b]-quinoline 8b-f. Furthermore, 3-[(3-aryl-4-oxothiazolidin-2-ylidene)amino]-1H-pyrazolo[3,4-b]quinolines 11a,b; 3-[(3-aryl-4-oxothiazin-2-ylidene)amino]-1H-pyrazolo[3,4-b]quinolines 12a,b and 3-(2-aryl-4-oxothiazolidin-3-yl)-1H-pyrazolo[3,4-b]quinolines 13a,b were synthesized. The antimicrobial activity was evaluated for most of the prepared compounds.     

Erratum to: 2-Substituted-8-methyl-3,6-dihydroimidazo [4,5-c]pyrazolo[3,4-e]pyridazine as an anti-inflammatory agent

A series of 8-methyl-2-substituted-3,6-dihydroimidazo[4,5-c]pyrazolo[3,4-e]pyridazine compounds have been synthesized in the present investigation utilizing Philips condensation (Philips, J Chem Soc 2393–2399, 1928). The anti-inflammatory activity of the synthesized compounds was evaluated using a carrageenin rat model.     

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 binding study on pyrazolo[4,5-c] [1,8]naphthyridines

Following our previous reports on pyrazolo[4,5-c]quinoline derivatives some isosteric pyrazolo[4,5-c] [1,8]naphthyridines were synthesized and tested for their ability to displace [3H]flunitrazepam from rat brain membranes. The lack of activity of the synthesized compounds and structure-activity relationships for the whole series are discussed.     

Synthesis, DNA-binding, and antiviral activity of certain pyrazolo[3,4-d]pyrimidine derivatives

Some new pyrazolo[3,4-d]pyrimidine derivatives have been prepared and tested for their antiviral and DNA-binding activities. Compounds 4, 5, and 6 showed high binding affinity to DNA at concentrations of 19, 27, and 28 micrograms/ml, respectively. On the other hand, compounds 6 and 10 reduced the number of viral plaques of Herpes simplex type-1 (HSV-1) by 66 and 41%, respectively. The detailed synthesis and spectroscopic and biological data are reported.     

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 and anti-inflammatory evaluation of some pyrazolo[3,4-b]pyridines

Novel series of pyrazolo[3,4-b]pyridines with basic skeleton different from the known COX inhibitors were synthesized from 5-amino-1-[4-(aminosulfonyl)phenyl]-3-phenyl-1H-pyrazole, which in turn was prepared by the condensation of (4-sulfamoylphenyl)hydrazine with α-cyanoacetophenone. All the newly synthesized compounds were tested for their in vivo anti-inflammatory activity by carrageenan-induced rat paw edema assay. Some of the most potent compounds were evaluated in different COX and LOX assays. Some of the new compounds were found to possess moderate anti-inflammatory activity.     

Synthesis of new pyrazolo[3,4‐d]pyrimidine derivatives and evaluation of their anti‐inflammatory and anticancer activities

This study reports the synthesis of two series of new purine bioisosteres comprising a pyrazolo[3,4‐d]pyrimidine scaffold linked to piperazine moiety through different amide linkages. The newly synthesized compounds were evaluated for anticancer activity against four cell lines (MDA‐MB‐231, MCF‐7, SF‐268, B16F‐10) and cyclooxygenase (COX‐2) protein expression inhibition in lipopolysaccharide (LPS)‐activated rat monocytes. The results revealed that most of the synthesized compounds showed moderate‐to‐high cytotoxic activity against at least one cell line, with compound 10b being the most active against all used cell lines (IC₅₀ values 5.5–11 μg/ml) comparable to cisplatin. In addition, six of these compounds ( 7b, 10a–d, and 12c ) demonstrated inhibition of LPS‐induced COX‐2 protein expression at low concentration (25 μg/ml) as compared to the control non‐stimulated cells and showed a COX‐2 selectivity index range comparable to diclofenac sodium. The overall results indicate that many of these pyrazolopyrimidine derivatives possess in vitro anti‐inflammatory and anticancer activities at varying doses, and the most active compounds will be subjected to in vivo pharmacological evaluation.     

Synthesis and analgesic activity of new tricyclic pyrazolo[3,4-b]pyridines

The title compounds have been obtained in a two-step synthesis from 5-amino-4-(1-cycloalkenyl)pyrazoles. Among the synthetized compounds, the 6,7,8,9-tetrahydro-1,3-dimethyl-3H-pyrazolo[3,4-c]isoquinoline, showed interesting antiinflammatory and analgesic activity.     

Structure-activity relationships of imidazo[4,5-f]quinoline partial structures and analogs. Discovery of pyrazolo[3,4-f]quinoline derivatives as potent immunostimulants.

Structure-activity studies have been carried out on a series of imidazo[4,5-f]quinoline derivatives reported to have potent in vivo immunostimulatory activity. This activity has been confirmed, and subtle structure-activity relationships have been uncovered which resulted in the identification of novel analogs (pyrazolo[3,4-f]quinoline derivatives, 7a,b) with potent in vivo effects in a mouse protection model. Regioisomeric pyrazolo[4,3-f]quinoline derivatives (6a,b) were shown to be inactive. Data are presented which support the notion that the in vivo activity is mediated by an immunostimulatory mechanism.