Synthesis and biological evaluation of pyrazolo[1,5-a]pyrimidine-3-carboxamide as antimicrobial agents

Synthesis of functionalized tetrahydrodibenzo[b,g][1,8]naphthyridin-1(2H)-ones through base-promoted annulation of quinoline-derived dipolarophiles and cyclic enaminones

An eco-friendly and metal-free method for the synthesis of tetrahydrodibenzo[b,g][1,8]naphthyridin-1(2H)-ones was established. Quinoline-derived dipolarophiles and cyclic enaminones as starting materials undergo a 1,4-Michael addition/SNAr tandem annulation reaction affording the target products. This approach features transition metal-free conditions, good functional group tolerance and operational simplicity.

Exploring novel derivatives of isatin-based Schiff bases as multi-target agents: design, synthesis, in vitro biological evaluation, and in silico ADMET analysis with molecular modeling simulations

Recently, scientists developed a powerful strategy called "one drug-multiple targets" to discover vital and unique therapies to fight the most challenging diseases. Novel derivatives of isatin-based Schiff bases 2-7 have been synthesized by the reaction of 3-hydrazino-isatin (1) with aryl aldehydes, hetero-aryl aldehydes, and dialdehydes. The structure of the synthesized derivatives was proved by physical and spectral analysis. Additionally, in vitro biological studies were performed, including antioxidant, anti-diabetic, anti-Alzheimer, and anti-arthritic activities. The four derivatives 3b, 5a, 5b, and 5c possess the highest activities. Among the four potent derivatives, compound 5a exhibited the highest antioxidant (TAC = 68.02 ± 0.15 mg gallic acid per g; IRP = 50.39 ± 0.11) and scavenging activities (ABTS = 53.98 ± 0.12% and DPPH = 8.65 ± 0.02 μg mL^-1). Furthermore, compound 5a exhibited an α-amylase inhibitory percentage of 57.64 ± 0.13% near the acarbose (ACA = 69.11 ± 0.15%) and displayed inhibitor activity of the acetylcholinesterase (AChE) enzyme = 36.38 ± 0.08%. Moreover, our work extended to determining the anti-arthritic effect, and compound 5a revealed good inhibitor activities with very close values for proteinase denaturation (PDI) = 39.59 ± 0.09% and proteinase inhibition (PI) = 36.39 ± 0.08%, compared to diclofenac sodium PDI = 49.33 ± 0.11% and PI = 41.88 ± 0.09%. Additionally, the quantum chemical calculations, including HOMO, LUMO, and energy band gap were determined, and in silico ADMET properties were predicted, and their probability was recorded. Finally, molecular docking simulations were performed inside α-amylase and acetylcholinesterase enzymes.

In vitro enzymatic evaluation of some pyrazolo[1,5-a]pyrimidine derivatives: Design, synthesis, antioxidant, anti-diabetic, anti-Alzheimer, and anti-arthritic activities with molecular modeling simulation

The strategy of utilizing nitrogen compounds in various biological applications has recently emerged as a powerful approach to exploring novel classes of therapeutics to face the challenge of diseases. A series of pyrazolo[1,5-a]pyrimidine-based compounds 3a-l and 5a-f were prepared by the direct cyclo-condensation reaction of 5-amino-1H-pyrazoles 1a, b with 2-(arylidene)malononitriles and 3-(dimethylamino)-1-aryl-prop-2-en-1-ones, respectively. The structures of the new pyrazolo[1,5-a]pyrimidine compounds were confirmed via spectroscopic techniques. The in vitro biological activities of all pyrazolo[1,5-a]pyrimidines 3a-l and 5a-f were evaluated by assaying total antioxidant capacity, iron-reducing power, the scavenging activity against 1-diphenyl-2-picryl-hydrazyl (DPPH) and 2, 2'-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radicals, anti-diabetic, anti-Alzheimer, and anti-arthritic biological activities. All compounds displayed good to potent bioactivity, and three compounds 3g, 3h, and 3l displayed the most active derivatives. Among these derivatives, compound 3l exhibited the highest antioxidant (total antioxidant capacity [TAC] = 83.09 mg gallic acid/g; iron-reducing power [IRP] = 47.93 µg/ml) and free radicals scavenging activities with (DPPH = 18.77 µg/ml; ABTS = 40.44%) compared with ascorbic acid (DPPH = 4.28 µg/ml; ABTS = 38.84%). Furthermore, compound 3l demonstrated the strongest inhibition of α-amylase with a percent inhibition of 72.91 ± 0.14 compared to acarbose = 67.92 ± 0.09%. Similarly, it displayed acetylcholinesterase inhibition of 62.80 ± 0.06%. However, compound 3i showed a significantly higher inhibition percentage for protein denaturation and proteinase at 20.66 ± 0.00 and 26.42 ± 0.06%, respectively. Additionally, some in silico ADMET properties were predicted and studied. Finally, molecular docking simulation was performed inside the active site of α-amylase and acetylcholinesterase to study their interactions.

Discovery of novel pyrazole and pyrazolo[1,5-a]pyrimidine derivatives as cyclooxygenase inhibitors (COX-1 and COX-2) using molecular modeling simulation

Searching for effective and selective anti-inflammatory agents, our study involved designing and synthesizing new pyrazole and pyrazolo[1,5-a]pyrimidine derivatives 4-11. The structures of the synthesized derivatives were confirmed using different spectroscopic techniques. Virtual screening was achieved for the newly designed derivatives using in silico docking simulation inside the active sites of four proteins classified as two cyclooxygenases (COX)-1 (PDB: 3KK6 and 4OIZ) and two COX-2 (PBD: 1CX2 and 3LN1). Among them, six derivatives 4c, 5b, 6a, 7a, 7b, and 10b displayed the highest binding energy. These derivatives were evaluated for their in vitro COX-1 and COX-2 inhibitory activities and their selectivity indexes were calculated. Additionally, these derivatives displayed IC₅₀ values ranging between 4.909 ± 0.25 and 57.53 ± 2.91 µM, and 3.289 ± 0.14 and 124 ± 5.32 µM, against COX-1 and COX-2, respectively. Furthermore, the tested derivatives were found to have selective inhibitory activity on the COX-2 enzyme. Surprisingly, the two pyrazole derivatives 4c and 5b were found to be the most active, with IC₅₀ values of 9.835 ± 0.50 and 4.909 ± 0.25 µM and 4.597 ± 0.20 and 3.289 ±  0.14 µM compared with meloxicam (1.879 ± 0.1 and 5.409 ±  0.23 µM) and celecoxib (5.439 ± 0.28 and 2.164 ± 0.09 µM) against COX-1/-2, respectively. Besides, two pyrazole derivatives, 4c and 5b, displayed a COX-1/COX-2 SI of 2.14 and 1.49. Computational techniques such as molecular docking, density function theory (DFT) calculation, and chemical absorption, distribution, metabolism, excretion, and toxicity evaluation were applied to explain the molecules' binding mode, chemical nature, drug likeness, and toxicity prediction.

Insights into the medicinal chemistry of heterocycles integrated with a pyrazolo[1,5-a]pyrimidine scaffold

Pyrazolo[1,5-a]pyrimidines are the dominant motif of many drugs; for instance, zaleplon and indiplon are sedative agents and ocinaplon was identified as an anxiolytic agent. The importance of this class of compounds lies in its varied and significant biological activities, and accordingly, considerable methods have been devised to prepare these compounds. Hence, other derivatives of this class of compounds were prepared by substitution reactions with different nucleophiles exploiting the activity of groups linked to the ring carbon and nitrogen atoms. The methods used vary through the condensation reactions of the aminopyrazoles with 1,2-allenic, enaminonitriles, enaminones, 1,3-diketones, unsaturated nitriles, or unsaturated ketones. Alternatively, these compounds are prepared through the reactions of acyclic reagents, as these methods were recently developed efficiently with high yields. The current review highlighted the recent progress of the therapeutic potential of pyrazolo[1,5-a]pyrimidines as antimicrobial, anticancer, antianxiety, anti-proliferative, analgesic, and antioxidant agents, carboxylesterase, translocator protein and PDE10A inhibitors, and selective kinase inhibitors.

Bicyclic 5-6 Systems: Comprehensive Synthetic Strategies for the Annulations of Pyrazolo[ 1,5-a]pyrimidines

Pyrazolopyrimidines are a privileged class of 5-6 bicyclic systems with three or four nitrogen atoms, including four possible isomeric structures. The significance of this class of compounds is that they can be applied in medical and pharmaceutical fields due to their unlimited biological aptitude, hence it is the basic skeleton of several synthetic drugs. The current review aimed to highlight all the synthetic routes that have been applied to construct the pyrazolo[1,5-a]pyrimidine ring systems up to date. The sections in this study included the synthesis of pyrazolo[1,5- a]pyrimidines by condensation reactions of 5-aminopyrazoles with each of β-diketones, 1,5-diketones, β- ketoaldehydes, α-cyanoaldehydes, β-enaminones, enamines, enaminonitriles, ethers, with unsaturated ketones, unsaturated thiones, unsaturated esters, unsaturated dienones "1,2-allenic", unsaturated aldehydes, unsaturated imines, and unsaturated nitriles. The routes adopted to synthesize this class of heterocyclic compounds were extended for ring construction from acyclic reagents and multicomponent reactions under catalytic or catalyst-free conditions.

A Compendium of the Most Promising Synthesized Organic Compounds against Several Fusarium oxysporum Species: Synthesis, Antifungal Activity, and Perspectives

Vascular wilt caused by F. oxysporum (FOX) is one of the main limitations of producing several agricultural products worldwide, causing economic losses between 40% and 100%. Various methods have been developed to control this phytopathogen, such as the cultural, biological, and chemical controls, the latter being the most widely used in the agricultural sector. The treatment of this fungus through systemic fungicides, although practical, brings problems because the agrochemical agents used have shown mutagenic effects on the fungus, increasing the pathogen's resistance. The design and the synthesis of novel synthetic antifungal agents used against FOX have been broadly studied in recent years. This review article presents a compendium of the synthetic methodologies during the last ten years as promissory, which can be used to afford novel and potential agrochemical agents. The revision is addressed from the structural core of the most active synthetic compounds against FOX. The synthetic methodologies implemented strategies based on cyclo condensation reactions, radical cyclization, electrocyclic closures, and carbon-carbon couplings by metal-organic catalysis. This revision contributes significantly to the organic chemistry, supplying novel alternatives for the use of more effective agrochemical agents against F. oxysporum.

Design, Synthesis, Anticancer Evaluation, Enzymatic Assays, and a Molecular Modeling Study of Novel Pyrazole-Indole Hybrids

The molecular hybridization concept has recently emerged as a powerful approach in drug discovery. A series of novel indole derivatives linked to the pyrazole moiety were designed and developed via a molecular hybridization protocol as antitumor agents. The target compounds (5a-j and 7a-e) were prepared by the reaction of 5-aminopyrazoles (1a-e) with N-substituted isatin (4a,b) and 1H-indole-3-carbaldehyde (6), respectively. All products were characterized via several analytical and spectroscopic techniques. Compounds (5a-j and 7a-e) were screened for their cytotoxicity activities in vitro against four human cancer types [human colorectal carcinoma (HCT-116), human breast adenocarcinoma (MCF-7), human liver carcinoma (HepG2), and human lung carcinoma (A549)] using the MTT assay. The obtained results showed that the newly synthesized compounds displayed good-to-excellent antitumor activity. For example, 5-((1H-indol-3-yl)methyleneamino)-N-phenyl-3-(phenylamino)-1H-pyrazole-4-carboxamide (7a) and 5-((1H-indol-3-yl)methyleneamino)-3-(phenylamino)-N-(4-methylphenyl)-1H-pyrazole-4-carboxamide (7b) provided excellent anticancer inhibition performance against the HepG2 cancer cell line with IC₅₀ values of 6.1 ± 1.9 and 7.9 ± 1.9 μM, respectively, compared to the standard reference drug, doxorubicin (IC₅₀ = 24.7 ± 3.2 μM). The two powerful anticancer compounds (7a and 7b) were further subjected to cell cycle analysis and apoptosis investigation in HepG2 using flow cytometry. We have also studied the enzymatic assay of these two compounds against some enzymes, namely, caspase-3, Bcl-2, Bax, and CDK-2. Interestingly, the molecular docking study revealed that compounds 7a and 7b could well embed in the active pocket of the CDK-2 enzyme via different interactions. Overall, the prepared pyrazole-indole hybrids (7a and 7b) can be proposed as strong anticancer candidate drugs against various cancer cell lines.

Sulfaguanidine Hybrid with Some New Pyridine-2-One Derivatives: Design, Synthesis, and Antimicrobial Activity against Multidrug-Resistant Bacteria as Dual DNA Gyrase and DHFR Inhibitors

Herein, a series of novel hybrid sulfaguanidine moieties, bearing 2-cyanoacrylamide 2a-d, pyridine-2-one 3-10, and 2-imino-2H-chromene-3-carboxamide 11, 12 derivatives, were synthesized, and their structure confirmed by spectral data and elemental analysis. All the synthesized compounds showed moderate to good antimicrobial activity against eight pathogens. The most promising six derivatives, 2a, 2b, 2d, 3a, 8, and 11, revealed to be best in inhibiting bacterial and fungal growth, thus showing bactericidal and fungicidal activity. These derivatives exhibited moderate to potent inhibition against DNA gyrase and DHFR enzymes, with three derivatives 2d, 3a, and 2a demonstrating inhibition of DNA gyrase, with IC₅₀ values of 18.17-23.87 µM, and of DHFR, with IC₅₀ values of 4.33-5.54 µM; their potency is near to that of the positive controls. Further, the six derivatives exhibited immunomodulatory potential and three derivatives, 2d, 8, and 11, were selected for further study and displayed an increase in spleen and thymus weight and enhanced the activation of CD4⁺ and CD8⁺ T lymphocytes. Finally, molecular docking and some AMED studies were performed.

Discovery of New Schiff Bases Tethered Pyrazole Moiety: Design, Synthesis, Biological Evaluation, and Molecular Docking Study as Dual Targeting DHFR/DNA Gyrase Inhibitors with Immunomodulatory Activity

A series of Bis-pyrazole Schiff bases (6a–d and 7a–d) and mono-pyrazole Schiff bases (8a–d and 9a–d) were designed and synthesized through the reaction of 5-aminopyrazoles 1a–d with aldehydes 2–5 using mild reaction condition with a good yield percentage. The chemical structure of newly formed Schiff bases tethered pyrazole core was confirmed based on spectral and experimental data. All the newly formed pyrazole Schiff bases were evaluated against eight pathogens (Gram-positive, Gram-negative, and fungi). The result exhibited that, most of them have good and broad activities. Among those, only six Schiff bases (6b, 7b, 7c, 8a, 8d, and 9b) displayed MIC values (0.97–62.5 µg/mL) compared to Tetracycline (15.62–62.5 µg/mL) and Amphotericin B (15.62–31.25 µg/mL), MBC values (1.94–87.5 µg/mL) and selectivity to tumor cell than normal cells. Immunomodulatory activities showed that the promising Schiff bases increase the immunomodulator effect of defense cell and the Schiff base 8a is the highest one by (Intra. killing activity = 136.5 ± 0.3%) having a pyrazole moiety as well as amide function (O=C-NH₂) and piperidinyl core. Furthermore, the most potent one exhibited broad activity depending on both MIC and MBC values. Moreover, to study the mechanism of these pyrazole Schiff bases, two active Schiff bases 8a and 9b from six derivatives were introduced to study the enzyme assay as dihydrofolate reductase (DHFR) on E. coli organism and DNA gyrase with two different organisms, S. aureus and B. subtilis, to determine the inhibitory activities with lower values in the case of DNA gyrase (8a and 9b) or nearly as DHFR compound 9b, while pyrazole 8a showed excellent inhibitory against all enzyme assay. The molecular docking study against dihydrofolate reductase and DNA gyrase were performed to study the binding between active site in the pocket with the two Schiff bases (8a and 9b) that exhibited good binding affinity with different bond types as H-bonding, aren-aren, and arene-cation interaction as well as study the physicochemical and pharmacokinetic properties of the two active Schiff bases 8a and 9b.

Antimicrobial evaluation of thiadiazino and thiazolo quinoxaline hybrids as potential DNA gyrase inhibitors; design, synthesis, characterization and morphological studies

A series of thiadiazino[5,6-b]quinoxaline and thiazolo[4,5-b]quinoxaline derivatives was designed and synthetized from the reaction of 2,3-dichloro-6-(morpholinosulfonyl)quinoxaline (2) with thiosemicarbazide or thiocarbohydrazide and thiourea derivatives to give nineteen quinoxaline derivatives 3-16. All the synthesized compounds were evaluated for in vitro antimicrobial potential against various bacteria and fungi strains that showed considerable antimicrobial activity against tested microorganisms. The most potent compounds 2, 7, 9, 10, 12 and 13c were exhibited bactericidal activity, in addition to fungistatic activity by dead live assay. Moreover, these compounds showed a significant result against all multi-drug resistance (MDRB) used especially compound 13c that displayed the best results with MICs of MDRB (1.95, 3.9, 2.6, 3.9 µg/mL) for stains used in this study, compared with Norfloxacin (1.25, 0.78, 1.57, 3.13 µg/mL). Also, cytotoxicity on normal cell (Vero cells ATCC CCL-81) by MTT assay was performed with lower toxicity results. Additionally, morphological studies, immunostimulatory potency and DNA gyrase inhibition assay of most active compounds was done. A molecular docking study has also been carried out to support the effective binding of the most promising compounds at the active site of the target enzyme S. aureus DNA gyrase (2XCT).

Biological Evaluation and Molecular Docking with In Silico Physicochemical, Pharmacokinetic and Toxicity Prediction of Pyrazolo[1,5-a]pyrimidines

Pyrazolo[1,5-a]pyrimidines 5a–c, 9a–c and 13a–i were synthesized for evaluation of their in vitro antimicrobial properties against some microorganisms and their immunomodulatory activity. The biological activities of pyrazolo[1,5-a]pyrimidines showed that the pyrazolo[1,5-a]pyrimidines (5c, 9a, 9c, 13a, 13c, 13d, 13e and 13h) displayed promising antimicrobial and immunomodulatory activities. Studying the in silico predicted physicochemical, pharmacokinetic, ADMET and drug-likeness properties for the pyrazolo[1,5-a]pyrimidines 5a–c, 9a–c and 13a–i confirmed that most of the compounds (i) were within the range set by Lipinski’s rule of five, (ii) show higher gastrointestinal absorption and inhibition of some CYP isoforms, and (iii) have a carcinogenicity test that was predicted as negative and hERG test that presented medium risk. Moreover, the molecular docking study demonstrated that the compounds 5c, 9a, 9c, 13a, 13c, 13d, 13e and 13h are potent inhibitors of 14-alpha demethylase, transpeptidase and alkaline phosphatase enzymes. This study could be valuable in the discovery of a new series of drugs.

An efficient and targeted synthetic approach towards new highly substituted 6-amino-pyrazolo[1,5-a]pyrimidines with α-glucosidase inhibitory activity

In an attempt to find novel α-glucosidase inhibitors, an efficient, straightforward reaction to synthesize a library of fully substituted 6-amino-pyrazolo[1,5-a]pyrimidines 3 has been investigated. Heating a mixture of α-azidochalcones 1 and 3-aminopyrazoles 2 under the mild condition afforded desired compounds with a large substrate scope in good to excellent yields. All obtained products were evaluated as α-glucosidase inhibitors and exhibited excellent potency with IC₅₀ values ranging from 15.2 ± 0.4 µM to 201.3 ± 4.2 µM. Among them, compound 3d was around 50-fold more potent than acarbose (IC₅₀ = 750.0 ± 1.5 µM) as standard inhibitor. Regarding product structures, kinetic study and molecular docking were carried out for two of the most potent ones.

Antibacterial Evaluation, In Silico Characters and Molecular Docking of Schiff Bases Derived from 5-aminopyrazoles

A series of Schiff bases 14-25 were designed and synthesized for evaluation of their antibacterial properties against multi-drug resistant bacteria (MDRB). The antibacterial activities of Schiff bases 14-25 showed that most of the synthesized compounds displayed a significant antibacterial activity. Assessment of in silico ADMET properties (absorption, distribution, metabolism, excretion and toxicity) of Schiff bases illustrates that all derivatives showed agreement to the Lipinski's rule of five. Further enzymatic assay aided by molecular docking study demonstrated that compound 18 is a potent inhibitor of staphylococcus aureus DNA gyrase and dihydrofolate reductase kinases. This study could be valuable in the discovery of new potent antimicrobial agents.

Promising Recent Strategies with Potential Clinical Translational Value to Combat Antibacterial Resistant Surge

Multiple drug resistance (MDR) for the treatment of bacterial infection has been a significant challenge since the beginning of the 21st century. Many of the small molecule-based antibiotic treatments have failed on numerous occasions due to a surge in MDR, which has claimed millions of lives worldwide. Small particles (SPs) consisting of metal, polymer or carbon nanoparticles (NPs) of different sizes, shapes and forms have shown considerable antibacterial effect over the past two decades. Unlike the classical small-molecule antibiotics, the small particles are less exposed so far to the bacteria to trigger a resistance mechanism, and hence have higher chances of fighting the challenge of the MDR process. Until recently, there has been limited progress of clinical treatments using NPs, despite ample reports of in vitro antibacterial efficacy. In this review, we discuss some recent and unconventional strategies that have explored the antibacterial efficacy of these small particles, alone and in combination with classical small molecules in vivo, and demonstrate possibilities that are favorable for clinical translations in near future.

Design, Synthesis and Antitumor Evaluation of Novel Pyrazolopyrimidines and Pyrazoloquinazolines

A series of N-aryl-7-aryl-pyrazolo[1,5-a]pyrimidines 18a⁻u and N-aryl-pyrazolo[1,5-a]quinazolines 25a⁻c were designed and synthesized via the reaction of 5-aminopyrazoles 11a⁻c with enaminones 12a⁻g or 19, respectively. The new compounds were screened for their in vitro antitumor activity toward liver (HepG-2) and breast (MCF-7) human cancer cells using 3-[4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide MTT assay. From the results, it was found that all compounds showed dose-dependent cytotoxic activities against both HepG-2 and MCF-7 cells. Two compounds 18o and 18a were selected for further investigations. Cell cycle analysis of liver (HepG-2) cells treated with 18o and breast (MCF-7) cells treated with 18a showed cell cycle arrest at G2/M phase and pro-apoptotic activity as indicated by annexin V-FITC staining.