Pyrazolo[3,4‐d]pyrimidine Derivatives as COX‐2 Selective Inhibitors: Synthesis and Molecular Modelling Studies

The pyrazolo[3,4‐d]pyrimidine system shows a multitude of interesting pharmacological properties. Owing to the potential anti‐inflammatory activity of 5‐benzamido‐pyrazolo[3,4‐d]pyrimidin‐4‐one derivatives and considering the easy synthesis of this class of compounds, a set of new 5‐benzamido‐1H‐pyrazolo[3,4‐d]pyrimidin‐4‐ones has been prepared in 42‐80% yields by reacting 5‐aminopyrazole‐4(N‐benzoyl)carbohydrazide derivatives and the opportune triethylorthoesters. Compounds 8a , b , 10a – d , and 11a , b revealed a superior inhibitory profile against COX‐2, when compared to that of reference standards NS398 and indomethacin. Molecular modelling studies confirmed the obtained biological results.     

4‐Substituted‐1‐phenyl‐1H‐pyrazolo[3,4‐d]pyrimidine Derivatives: Design,Synthesis, Antitumor and EGFR Tyrosine Kinase Inhibitory Activity

Four series of some 4‐substituted‐1‐phenyl‐1H‐pyrazolo[3,4‐d]pyrimidine derivatives 5a – f , 6a – f , 8a – f , and 9a – f were designed to be screened for their antitumor activity. All compounds were evaluated against breast (MCF‐7) and lung (A‐549) cell lines. Six compounds 5a , 5b , 6b , 6e , 9e , and 9f displaying activity against both cell lines were further estimated for their EGFR‐TK inhibitory activity where they revealed 41–91% inhibition and compound 6b elicited the highest activity (91%). A docking study of these compounds into the ATP‐binding site of EGFR‐TK demonstrated their binding mode where H‐bonding interaction with Met793 through N¹ of pyrimidine or N² of pyrazole was observed.     

Synthesis and Antiproliferative Activitiy of Novel Diaryl Ureas Possessing a 4H‐Pyrido[1,2‐a]pyrimidin‐4‐one Group

We herein disclose a series of novel diaryl urea derivatives possessing a 4H‐pyrido[1,2‐a]pyrimidin‐4‐one group as novel potent anticancer compounds. The structures were confirmed by IR, ¹H‐NMR, and MS. All the compounds were screened for their antiprofilerative activity agaist the human breast cancer cell line (MDA‐MB‐231). The pharmacological results indicated that most of the compounds showed moderate activity. The best of this series is compound 4c (IC₅₀ = 0.7 μmol/L), with a potency 3.6‐fold higher than Sorafenib (IC₅₀ = 2.5 μmol/L), which was approved in 2005.     

Activated Nitriles in Heterocyclic Chemistry. A Novel Synthesis of Pyridones,Pyrazolo[1,5-a]pyrimidines and Pyrazolo[1,5-b]oxazines

Several new pyridones, pyrazolo[1,5-a]pyrimidines and pyrazolo[1,5-b]oxazines were prepared from the cyanoacetohydrazide derivatives 1, 11 and the cinnamonitrile derivatives 2a – c .     

Synthesis and antitumor activity of isolongifoleno[7,8‐d]thiazolo[3,2‐a]pyrimidine derivatives via enhancing ROS level

A series of novel isolongifoleno[7,8‐d]thiazolo[3,2‐a]pyrimidine derivatives ( 4a – 4x ) were synthesized from isolongifolanone according fragment‐based design strategy, and their anticancer activity against human aortic smooth muscle cells (HASMC), human breast cancer (MCF‐7) cells, human cervical cancer (HeLa) cells, and human liver cancer (HepG2) cells were investigated. Results of the anticancer activity illustrated that most of the compounds showed potent antitumor activity and compound 4i proved to be the most active derivative with IC₅₀ values of 0.33 ± 0.24 (for MCF‐7 cells), 0.52 ± 0.13 (for HeLa cells), and 3.09 ± 0.11 μM (for HepG2 cells), respectively. Moreover, we assessed the effects of 4i on cell apoptosis, cell cycle distribution, mitochondrial membrane potential, and reactive oxygen species (ROS) generation. The results indicated that compound 4i altered mitochondrial membrane potential and produced ROS leading to cell apoptosis of MCF‐7 cells in a dose‐dependent manner, however, without affecting cell cycle progression. These findings suggested that 4i was an effective compound and provided a promising candidate for anticancer drugs.     

Synthesis and Biological Evaluation of Novel Pyrazoles and Pyrazolo[3,4‐d]pyrimidines Incorporating a Benzenesulfonamide Moiety

Synthesis and biological evaluation of novel pyrazoles and pyrazolo[3,4‐d]pyrimidines are reported. Fourteen compounds were selected by the NCI and tested for their preliminary in‐vitro anticancer activity, whereas all the synthesized compounds were evaluated for their in‐vitro antimicrobial activity. Compound 12a was proven to possess the highest anticancer activity with a broad spectrum profile. It showed particular effectiveness towards leukemia HL‐60 (TB), K‐562, non‐small cell lung cancer NCI‐H23, and colon cancer HT 29, KM 12 cell lines (GI₅₀ = 6.59, 4.44, 1.37, 3.33, and 9.63 μM, respectively). Out of the synthesized compounds, thirteen derivatives were found to display pronounced antimicrobial activity especially against P. aeruginosa. Compounds 2c , 5b , 10 , 11b , 17b , 18b , and 19 were proven to be the most active with a broad spectrum of activity. Compound 19 was found to be equipotent to ampicillin against B. subtilis, whereas compounds 11b and 19 were four times superior to ampicillin against P. aeruginosa, while compounds 5b and 18b were equipotent to ampicillin against the same organism. Moreover, compounds 2c , 10 , and 11b were nearly equipotent to ampicillin against E. coli. On the other hand, compounds 2c , 5b , 10 , 11a , 17b , and 18b exerted nearly half the activity of clotrimazole against C. albicans.     

Fluorinated 1,2,4‐Triazolo[1,5‐a]pyrimidine‐6‐carboxylic Acid Derivatives as Antimycobacterial Agents

A series of fluorinated 1,2,4‐triazolo[1,5‐a]pyrimidine‐6‐carboxylic acid derivatives was designed and synthesized as fluoroquinolone analogues. The synthesized compounds were screened against Mycobacterium tuberculosis H₃₇R_v strain at 6.25 μg/mL concentration. Compound 4 , the 7‐oxo‐2‐(trifluoromethyl)‐4,7‐dihydro‐1,2,4‐triazolo[5,1‐a]pyrimidine‐6‐carboxylic acid was found to be a very potent inhibitor, being able to inhibit 92% growth of M. tuberculosis H₃₇R_v at 6.25 μg/mL concentration. At the same time, it proofed to be nontoxic to mammalian cells (IC₅₀ > 62.5 μg/mL in VERO cells).     

Synthesis and Anticonvulsant Activity of 6‐Alkoxy‐[1,2,4]Triazolo[3,4‐a]Phthalazines

A new series of 6‐alkoxy‐[1,2,4]triazolo[3,4‐a]phthalazines ( 3a – 3v ) were synthesized and their anticonvulsant activity and neurotoxicity were evaluated by the maximal electroshock test and the rotarod test respectively. Significant anticonvulsant activity was displayed by a number of compounds. The most promising compounds 6‐(4‐chlorobenzyloxy)‐[1,2,4]triazolo[3,4‐a]phthalazine ( 3f) and 6‐heptyloxy‐[1,2,4]triazolo[3,4‐a]phthalazine ( 3s) showed a median effective dose of 7.1 and 11.0 mg/kg, and had protective index value of 5.2 and 8.0 respectively. The two compounds were further found to have potent activity against seizures induced by pentylenetetrazole, isoniazid, thiosemicarbazide, 3‐mercaptopropionic acid but not seizures induced by strychnine, indicating that the two compounds might function by enhancing gamma‐aminobutyric acid neurotransmission.     

Synthesis and Biological Evaluation of a Series of Substituted Pyrazolo[3,4-d]-1,2,3-triazoles and Pyrazolo[3,4-d]oxazoles

In view of the biological relevance of triazole-based heterocyclic structures as antifungal, antiviral, and antitumor agents, we have synthesized a series of substituted pyrazolo[3,4-d]-1,2,3-triazoles ( 2e–h, 2j, 4b ) which we evaluated for their cytostatic and antiviral (HIV-1 included) activity and for their capability to inhibit the multiplication of various human pathogenic fungi and bacteria. Moreover, the biological activities of a few compounds, namely pyrazolo[3,4-d]oxazoles ( 3a–e ) and pyrazolo[3,4-d]-1,2,3-triazoles ( 2a–d, 4a, 5 ), previously obtained by us but not investigated for their biological activity, were also studied. Only compounds 3a–e were endowed with a significative antiproliferative activity on the human lymphoblastoid cell line MT-4 cells. All pyrazole derivatives proved ineffective in protecting cell cultures against the HIV-1-induced cytopathogenicity, and none of the compounds was active against the bacteria and fungi tested.     

Thieno[2,3‐d]pyrimidines in the Synthesis of Antitumor and Antioxidant Agents

Dimethyl acetylenedicarboxylate, ethyl propiolate, and E‐dibenzoylethylene react with thienopyrimidines (cyclo‐pentyl, ‐hexyl, and ‐heptyl) derivatives to form thiazolo[3,2‐a]thieno‐[2,3‐d]pyrimidin‐2‐ylidene) acetates, thieno[2,3‐d]pyrimidin‐2‐ylthioacrylates, and thieno[2′,3′:4,5]pyrimido[2,1‐b][1,3]thiazin‐6‐ones, respectively. Reactions proceed via cyclization and thio‐addition processes. Some derivatives of thienopyrimidines showed high inhibition of Hep‐G2 cell growth compared with the growth of untreated control cells. However, the fused heptyl of thienopyrimidothiazines indicates a promising specific antitumor agent against Hep‐G2 cells with IC₅₀ < 20 μM.     

Discovery of novel pyrrolopyrimidine/pyrazolopyrimidine derivatives bearing 1,2,3‐triazole moiety as c‐Met kinase inhibitors

Six series of pyrrolo[2,3‐d]pyrimidine and pyrazolo[3,4‐d]pyrimidine derivatives bearing 1,2,3‐triazole moiety were designed and synthesized, and some bio‐evaluation was also carried out. As a result, four points can be summarized: Firstly, some of compounds exhibited excellent cytotoxicity activity and selectivity with the IC₅₀ values in single‐digit μm level. In particular, the most promising compound 16d showed equal activity to lead compound foretinib against A549, HepG2, and MCF‐7 cell lines, with the IC₅₀ values of 4.79 ± 0.82, 2.03 ± 0.39, and 2.90 ± 0.43 μm , respectively. Secondly, the SARs and docking studies indicated that the in vitro antitumor activity of pyrrolo[2,3‐d]pyrimidine derivatives bearing 1,2,3‐triazole moiety was superior to the pyrazolo[3,4‐d]pyrimidine derivatives bearing 1,2,3‐triazole moiety. Thirdly, three selected compounds ( 16d , 18d , and 20d ) were further evaluated for inhibitory activity against the c‐Met kinase, and the 16d could inhibit the c‐Met kinase selectively by experiments of enzyme‐based selectivity. What is more, 16d could induce apoptosis of HepG2 cells and inhibitor the cell cycle of HepG2 on G2/M phase by acridine orange staining and cell cycle experiments, respectively.     

Synthesis and structure–activity relationships of pyrazolo‐[3,4‐b]pyridine derivatives as adenosine 5'‐monophosphate‐activated protein kinase activators

A series of pyrazolo[3,4‐b]pyridine derivatives were designed, synthesized, and evaluated for their activation activity toward adenosine 5'‐monophosphate‐activated protein kinase (AMPK). According to the enzyme activity, the pyrazole N?H exposure and para substitution on the diphenyl group were proved to be essential for the activation potency. Compound 17f showed equal activation compared with A‐769662. In the molecular modeling study, compound 17f exhibited important hydrogen bond interaction with Lys29, Asp88, and Arg83. 3‐(4,5‐Dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide assays on the NRK‐49F cell line showed that potent enzyme activators could effectively inhibit cell proliferation, especially for 17f (EC₅₀ [AMPKα1γ1β1] = 0.42 μM, efficacy = 79%; IC₅₀ [NRK‐49F cell line] = 0.78 μM). These results might provide new insights to explore novel AMPK activators.     

Synthesis and In‐Vitro Anti‐Hepatitis‐B Virus Activity of 6H‐[1]Benzothiopyrano[4,3‐b] quinolin‐10‐ols

A series of 9‐methoxy‐6H‐[1]benzothiopyrano[4,3‐b]quinolin‐10‐ols with a Mannich side chain were synthesized and evaluated for their anti‐Hepatitis B virus (HBV) activity in HepG2.2.15 cells. Some compounds showed significant anti‐HBV activity with IC₅₀ values less than 41 μM. Among them, compound 9b was the most effective anti‐HBV agent (IC₅₀ = 1.7 μM, SI = 60.3).     

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.     

Reactions with Heterocyclic Amidines,XI. Syntheses of New 2-Aminopyrazolo[1,5—a]pyrimidines and 2-Amino[1,5-c]-as-triazines

Several new aminopyrazolo[1,5—a]pyrimidines were synthesised by condensation of 3,5-diamino-4-(ethoxycarbonyl)pyrazole (1) with β-bifunctional reagents. The azo analogues of pyrazolo[1,5—a]pyrimidines, i. e. pyrazolo[1,4-c]-as-triazines, were synthesised by coupling of diazotized 1 with agents containing active hydrogen.     

Design and synthesis of 1,2,4‐triazolo[1,5‐a]pyrimidine derivatives as PDE 4B inhibitors endowed with bronchodilator activity

A series of 1,2,4‐triazolo[1,5‐a]pyrimidine derivatives was designed, synthesized, and screened for their phosphodiesterase (PDE 4B) inhibitory activity and bronchodilation ability. Compound 7e showed 41.80% PDE 4B inhibition at 10 µM. Eight compounds were screened for their bronchodilator activity, where compounds 7f and 7e elicited promising bronchodilator activity with EC₅₀ values of 18.6 and 57.1 µM, respectively, compared to theophylline (EC₅₀ = 425 µM). Molecular docking at the PDE 4B active site revealed a binding mode and docking scores comparable to those of a reference ligand, consistent with their PDE 4B inhibition activity.     

Synthesis of [3H]‐labelled 4‐[Ethyl[2,5,6‐trimethyl‐7‐(2,4,6‐trimethylphenyl)pyrrolo[2,3‐d]pyrimidin‐4‐yl]amino]‐2,3‐[3H]‐butan‐1‐ol: a high affinity radioligand for the corticotropin‐releasing hormone type 1 receptor

[³H]‐Labelled 4‐[ethyl[2,5,6‐trimethyl‐7‐(2,4,6‐trimethylphenyl)pyrrolo[2,3‐d]pyrimidin‐4‐yl]amino]‐2,3‐[³H]‐butan‐1‐ol ( 3b ) was prepared as a novel non‐peptidic radiolabelled high affinity antagonist of the corticotropin‐releasing hormone type 1 receptor (CRHR₁) that could be useful as a more stable and receptor‐selective alternative to the radiolabelled peptides now used to label the CRHR₁ receptor for displacement studies in cell‐based binding assays. The precursor (Z)‐4‐[ethyl[2,5,6‐trimethyl‐7‐(2,4,6‐trimethylphenyl)pyrrolo[2,3‐d]pyrimidin‐4‐yl]amino]but‐2‐en‐1‐ol ( 2 ) was reduced with tritium gas using palladium as the catalyst. After HPLC purification 3b was obtained with a specific activity of 35 Ci/mmol in high radiochemical purity (>97%). Copyright © 2006 John Wiley & Sons, Ltd.     

Design,synthesis, and molecular docking study of 3H‐imidazole[4,5‐c]pyridine derivatives as CDK2 inhibitors

A novel series of imidazo[4,5‐c]pyridine‐based CDK2 inhibitors were designed from the structure of CYC202 via scaffold hopping strategy. These compounds were synthesized and biologically evaluated for their CDK2 inhibitory and in vitro anti‐proliferation potential against cancer cell lines. Several compounds exhibited potent CDK2 inhibition with IC₅₀ values of less than 1 µM. The most potent compound 5b showed excellent CDK2 inhibitory (IC₅₀ = 21 nM) and in vitro anti‐proliferation activity against three different cell lines (HL60, A549, and HCT116). The molecular docking and dynamic studies portrayed the potential binding mechanism between 5b and CDK2, and several key interactions between them were observed, which would be the reason for its potent CDK2 inhibitory and anti‐proliferation activities. Therefore, the pyridin‐3‐ylmethyl moiety would serve as an excellent pharmacophore for the development of novel CDK2 inhibitors for targeted anti‐cancer therapy.

     

Design,synthesis, and biological evaluation of novel 4‐phenoxypyridine derivatives as potential antitumor agents

A series of novel 4‐phenoxypyridine derivatives containing the 4‐oxo‐1,4‐dihydropyridazine‐3‐carboxamide moiety were synthesized and evaluated for their in vitro cytotoxic activity against the A549 cancer cell line, and some compounds were further examined for their cytotoxic activity against the H460, BGC823, MKN45, and HT‐29 cancer cell lines. Most of the compounds exhibited moderate to significant cytotoxicity. The most promising compound 15b (with VEGFR2 inhibitory concentration [IC₅₀] value of 0.23 μM) showed remarkable cytotoxicity against A549, BGC‐823, MKN45, H460, and HT‐29 cells, with IC₅₀ values of 0.75, 1.68, 2.63, 5.08 and 7.22 μM, respectively. Their preliminary structure‐activity relationship studies indicate that electron‐withdrawing groups on the terminal phenyl rings are beneficial for improving the antitumor activity. Moreover, treatment of A549 cells with compound 15b resulted in cell cycle arrest in the G₀/G₁ phase in a dose‐dependent manner. Further apoptotic studies and acridine orange/ethidium bromide staining were also performed on A549 cells, which showed that compound 15b could induce apoptosis. Wound‐healing assay results indicated that compound 15b strongly inhibited A549 cell motility.     

Synthesis and Anticonvulsant Activity of 5‐Phenyl‐[1,2,4]‐triazolo[4,3‐a]quinolines

A series of novel 5‐phenyl‐[1,2,4]‐triazolo[4,3‐a]quinoline derivatives was synthesized by the cyclization of 2‐chloro‐4‐phenyl‐1,2‐dihydronaphthalene with formohydrazide. The starting material 2‐chloro‐4‐phenyl‐1,2‐dihydronaphthalene was synthesized from ethyl‐3‐oxo‐3‐phenylpropanoate and substituted aniline. Their anticonvulsant activities were evaluated by the maximal electroshock (MES) test and their neurotoxicity was evaluated by the rotarod neurotoxicity test (Tox). The maximal electroshock test showed that 7‐hexyloxy‐5‐phenyl‐[1,2,4]‐triazolo[4,3‐a]quinoline 4f was found to be the most potent compound with an ED₅₀ value of 6.5 mg/kg and a protective index (PI = ED₅₀ / TD₅₀) value of 35.1, which was much higher than the PI of the reference drug phenytoin.