The synthesis and antiviral activity of 4-fluoro-1-beta-D-ribofuranosyl-1H-pyrazole-3-carboxamide

N-Heterocycles as Promising Antiviral Agents: A Comprehensive Overview

Viruses are a real threat to every organism at any stage of life leading to extensive infections and casualties. N-heterocycles can affect the viral life cycle at many points, including viral entrance into host cells, viral genome replication, and the production of novel viral species. Certain N-heterocycles can also stimulate the host's immune system, producing antiviral cytokines and chemokines that can stop the reproduction of viruses. This review focused on recent five- or six-membered synthetic N-heterocyclic molecules showing antiviral activity through SAR analyses. The review will assist in identifying robust scaffolds that might be utilized to create effective antiviral drugs with either no or few side effects.

Ultrasound-Assisted 1,3-Dipolar Cycloadditions Reaction Utilizing Ni-Mg-Fe LDH: A Green and Sustainable Perspective

Ultrasound-assisted synthesis of novel pyrazoles using Ni-Mg-Fe LDH as a catalyst in cyclopentyl methyl ether (CPME) is introduced. Different LDHs were tested as a catalyst for the synthesis of pyrazoles via a 1,3-dipolar cycloaddition reaction. Among them, Ni-Mg-Fe LDH was the superior catalyst for this reaction. This protocol offered high yields, a short reaction time, and a green solvent, and with the reuse of this catalyst six times with the same activity, it could be regarded as an ecofriendly, greener process. The NiMgFe LDH catalyst with the smallest particle size (29 nm) and largest surface area showed its superior efficacy for the 1,3 dipolar cycloaddition rection and can be successfully used in up to six catalytic cycles with little loss of catalytic activity. A plausible mechanism for this reaction over the Ni-Mg-Fe LDH is proposed.

Azole-pyrimidine Hybrid Anticancer Agents: A Review of Molecular Structure, Structure Activity Relationship and Molecular Docking

Cancer has emerged as one of the leading causes of deaths globally partly due to the steady rise in anticancer drug resistance. Pyrimidine and pyrimidine-fused heterocycles are some of the privileged scaffolds in medicine, as they possess diverse biological properties. Pyrimidines containing azole nucleus possesses inestimable anticancer potency and has enormous potential to conduct the regulation of cellular pathways for selective anticancer activity. The present review outlines the molecular structure of pyrimidine-fused azoles with significant anticancer activity. The structure activity relationship and molecular docking studies have also been discussed. The current review is the first complete compilation of significant literature on the proposed topic from 2016 to 2020. The information contained in this review offers a useful insight to chemists in the design of new and potent anticancer azole-pyrimidine analogues.

Antibacterial evaluation and molecular docking studies of pyrazole-thiosemicarbazones and their pyrazole-thiazolidinone conjugates

A library of pyrazole-thiazolidinone conjugates was synthesized using a molecular hybridization approach through a Vilsmeier-Haack reaction. The compounds were tested for anti-microbial activity against two Gram-positive bacteria (Staphylococcus aureus and methicillin-resistant Staphylococcus aureus) and four Gram-negative bacteria (Escherichia coli, Salmonella typhimurium, Klebsiella pneumonia and Pseudomonas aeruginosa). Among the compounds tested, 3-((2,4-dichlorophenyl)-1-(2,4-dinitrophenyl)-1H-pyrazol-yl)methylene)hydrazinecarbothioamide (3a) and 2-((3-(2-chlorophenyl)-1-(2,4 dinitrophenyl)-1H-pyrazol-4-yl)methyleneamino)thiazolidin-4-one (4b) emerged as the most potent anti-microbial compounds with minimum bactericidal concentrations of < 0.2 µM against MRSA and S. aureus. Structure-activity relationship analysis further revealed that the presence of 2,4-dichloro moiety surprisingly influenced the activity of the compounds. Molecular docking studies of the compounds into the crystal structure of topoisomerase II and topoisomerase IV suggest that compounds 3a and 4b preferably interact with the targets through hydrogen bonding.

Synthetic, Structural, and Anticancer Activity Evaluation Studies on Novel Pyrazolylnucleosides

The synthesis of novel pyrazolylnucleosides 3a–e, 4a–e, 5a–e, and 6a–e are described. The structures of the regioisomers were elucidated by using extensive NMR studies. The pyrazolylnucleosides 5a–e and 6a–e were screened for anticancer activities on sixty human tumor cell lines. The compound 6e showed good activity against 39 cancer cell lines. In particular, it showed significant inhibition against the lung cancer cell line Hop-92 (GI₅₀ 9.3 µM) and breast cancer cell line HS 578T (GI₅₀ 3.0 µM).

Synthesis and Antioxidant Evaluation of Dihydropyrimidinone Integrated Pyrazoles

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A series of novel ethyl 6-[2-(3-aryl-1-phenyl-1H-pyrazol-4-yl)vinyl]-2-oxo-4-phenyl- 1,2,3,4-tetrahydropyrimidine-5-carboxylates (9a-9d) has been synthesized by adopting a multistep synthetic strategy. The structure of the targets was confirmed on the basis of physical and spectral techniques. The synthetically achieved targets were evaluated for their antioxidant activity by in-vitro DPPH free radical scavenging assay. Of the chemical entities screened, most of them exhibit good to better radical scavenging profile and among those, the nitro substituent bearing molecule 9c displayed the highest activity (82%) with IC50 value 621.6 μM. Further, as a representative molecule, compound 9a has been subjected to density functional theory calculations employing B3LYP method with 6311(++G) basis set to optimize its structure.

Design, Synthesis and In Vitro Evaluation of Novel Anti-HIV 3-Pyrazol-3- yl-Pyridin-2-One Analogs

Background:

Natural products have shown potent anti-HIV activity, but some of these also possess toxicity. The pharmacophoric fragments of these natural products have scope of combination with other pharmacophoric fragment and derivatization to reduce toxicity and increase the potency. Combination of natural product fragments from different classes of anti–HIV compounds may lead to a new class of potent anti–HIV agents.

Objective:

Design, in silico prediction of drug-likeness, ADMET properties and synthesis of pyrazol– pyridones. Evaluation of the anti–HIV–1 activity of synthesized pyrazol–pyridones.

Methods:

Pyrazol–pyridones were designed by combining reported anti–HIV pharmacophoric fragments. Designed molecules were synthesized after in silico prediction of drug-likeness and ADMET properties. Compounds were evaluated for activity against HIV–1VB59 and HIV–1UG070.

Results:

QED value of designed pyrazol–pyridones was greater than the known drug zidovudine. The designed compounds were predicted to be noncarcinogenic and nonmutagenic in nature. Seventeen novel pyrazol–pyridones were synthesized with good yield. Compound 6q and 6l showed activity with IC50 values 6.14 µM and 15.34 µM against HIV–1VB59 and 16.21 µM and 18.21 µM against HIV–1UG070, respectively.

Conclusion:

Compound 6q was found to be most potent among the synthesized compounds with a therapeutic index of 54.31against HIV–1VB59. This is the first report of anti–HIV–1 activity of pyrazol–pyridone class of compounds. Although the anti–HIV–1 activity of these compounds is moderate, this study opens up a new class for exploration of chemical space for anti–HIV–1 activity.

Efficient synthesis, reactions and spectral characterization of pyrazolo[4’,3’:4,5]thieno[3,2-d] pyrimidines and related heterocycles

New pyrazolothienopyrimidines were synthesized. The key intermediate 4-aminothieno[2,3-c]pyrazole-5-carbonitrile 1 was converted to the chloroacetyl amino derivative 2 followed by nucleophilic substitution and Dimorth rearrangement upon treatment with nitrogen nucleophiles to give the pyrimidinones 3a-c. Treatment of 3a with formaldehyde and with triethyl orthoformate afforded the respective tetracyclic derivatives 4 and 5. Condensation of the amino group in the o-aminocarbonitrile 1 with triethyl orthoformate followed by cycloaddition reaction with hydrazine led to the formation of pyrazolothienopyrimidine 8. Compound 8 was used as a synthetic precursor to heterocyclic compounds comprised of pyrazole, triazole, triazine, and triazepine derivatives.

Serendipitous Formation of 2H-Pyrazolo[3,4-d]pyridazin-7(6H)-ones from 3-Arylsydnones

Fused nitrogen heterocyclesnamely, pyrazolo[3,4-d]pyridazin-7(6H)-ones have been obtained by exploiting the 1,3-dipolar nature of N-arylsydnones, from hydrazones of 3-aryl-4-acetylsydnones via the Vilsmeier-Haack strategy. Facile intramolecular nucleophilic addition followed by CO₂ elimination under reflux or upon microwave irradiation was presented. Plausible mechanisms for the formation of the title compounds are proffered. Structure confirmatory evidence came from single-crystal X-ray crystallography.

Synthesis and Pharmacological Activities of Pyrazole Derivatives: A Review

Pyrazole and its derivatives are considered a pharmacologically important active scaffold that possesses almost all types of pharmacological activities. The presence of this nucleus in pharmacological agents of diverse therapeutic categories such as celecoxib, a potent anti-inflammatory, the antipsychotic CDPPB, the anti-obesity drug rimonabant, difenamizole, an analgesic, betazole, a H2-receptor agonist and the antidepressant agent fezolamide have proved the pharmacological potential of the pyrazole moiety. Owing to this diversity in the biological field, this nucleus has attracted the attention of many researchers to study its skeleton chemically and biologically. This review highlights the different synthesis methods and the pharmacological properties of pyrazole derivatives. Studies on the synthesis and biological activity of pyrazole derivatives developed by many scientists around the globe are reported.

Synthesis and Pharmacological Activities of Pyrazole Derivatives: A Review

Pyrazole and its derivatives are considered a pharmacologically important active scaffold that possesses almost all types of pharmacological activities. The presence of this nucleus in pharmacological agents of diverse therapeutic categories such as celecoxib, a potent anti-inflammatory, the antipsychotic CDPPB, the anti-obesity drug rimonabant, difenamizole, an analgesic, betazole, a H2-receptor agonist and the antidepressant agent fezolamide have proved the pharmacological potential of the pyrazole moiety. Owing to this diversity in the biological field, this nucleus has attracted the attention of many researchers to study its skeleton chemically and biologically. This review highlights the different synthesis methods and the pharmacological properties of pyrazole derivatives. Studies on the synthesis and biological activity of pyrazole derivatives developed by many scientists around the globe are reported.

Synthesis, DNA binding and in-vitro cytotoxicity studies on novel bis-pyrazoles

A new series of bis-pyrazoles 6a-t were synthesized from 3,5-dimethyl pyrazole using sequential approach. All these compounds were characterized by IR, ¹H NMR, ¹³C NMR and mass spectral data. The interaction of newly synthesized bis-pyrazoles with DNA was investigated through molecular docking and absorption spectroscopic technique. Among all bis-pyrazoles compounds, the 6h compound showed lower conformational energy through in silico analysis. The interaction of each molecule in this series 6a-t with the various concentrations of DNA was examined through the UV-visible spectroscopic studies. The UV-visible spectroscopy studies on the specific binding of compound 6a, 6b, 6g, 6h, 6d, 6i, 6k, 6n, 6s with DNA have exhibited spectral shifts and the results were discussed. In further the compounds 6a-t were subjected to the in-vitro cytotoxicity studies against human pancreatic adenocarcinoma, human non-small cell lung carcinoma cell lines. Among the screened compounds, N-(3-isopropoxy-1-isopropyl-4-(3,5-dimethyl-1H-pyrazol-1-yl)-1H-pyrazol-5-yl)cyclobutane carboxamide and N-(5'-Isopropoxy-2'-isopropyl-3,5-dimethyl-2'H-[1,4'] bipyrazolyl-3'-yl)-dimethane sulfonamide were found as lead molecules since they have exhibited promising activity against both the cancer cell lines used in this study, whereas the compounds 4-(trifluoromethyl)-N-(3-isopropoxy-1-isopropyl-4-(3,5-dimethyl-2H-pyrrol-2-yl)-1H-pyrazol-5-yl)benzamide and 2,6-difluoro-N-(3-isopropoxy-1-isopropyl-4-(3,5-dimethyl-2H-pyrrol-2-yl)-1H-pyrazol-5-yl) benzamide were found to be active against the pancreatic cell line only. Rest all the other compounds were found to exhibit moderate to good activity towards both the cell lines.

Synthesis, anti-inflammatory, analgesic, COX1/2-inhibitory activity, and molecular docking studies of hybrid pyrazole analogues

This article reports on the design, synthesis, and pharmacological activity of a new series of hybrid pyrazole analogues: 5a–5u. Among the series 5a–5u, the compounds 5u and 5s exhibited potent anti-inflammatory activity of 80.63% and 78.09% and inhibition of 80.87% and 76.56% compared with the standard drug ibuprofen, which showed 81.32% and 79.23% inhibition after 3 and 4 hours, respectively. On the basis of in vivo studies, 12 compounds were selected for assessment of their in vitro inhibitory action against COX1/2 and TNFα. The compounds 5u and 5s showed high COX2-inhibitory activity, with half-maximal inhibitory concentrations of 1.79 and 2.51 μM and selectivity index values of 72.73 and 65.75, respectively, comparable to celecoxib (selectivity index =78.06). These selected compounds were also tested for TNFα, cytotoxicity, and ulcerogenicity. Docking studies were also carried out to determine possible interactions of the potent compounds (5u and 5s), which also showed high docking scores of −12.907 and −12.24 compared to celecoxib, with a −9.924 docking score. These selective COX2 inhibitors were docked into the active site of COX2, and showed the same orientation and binding mode to that of celecoxib (selective COX2 inhibitor). Docking studies also showed that the SO₂NH₂ of 5u and 5s is inserted deep inside the selective pocket of the COX2-active site and formed a hydrogen-bond interaction with His90, Arg513, Phe518, Ser353, Gln192, and Ile517, which was further validated by superimposed docked pose with celecoxib.

3-Substituted pyrazoles and 4-substituted triazoles as inhibitors of human 15-lipoxygenase-1

Investigation of 1N-substituted pyrazole-3-carboxanilides as 15-lipoxygenase-1 (15-LOX-1) inhibitors demonstrated that the 1N-substituent was not essential for activity or selectivity. Additional halogen substituents on the pyrazole ring, however, increased activity. Further development led to triazole-4-carboxanilides and 2-(3-pyrazolyl) benzoxazoles, which are potent and selective 15-LOX-1 inhibitors.

Recent progress on pyrazole scaffold-based antimycobacterial agents

New and reemerging infectious diseases will continue to pose serious global health threats well into the 21st century and according to the World Health Organization report, these are still the leading cause of death among humans worldwide. Among infectious diseases, tuberculosis claims approximately 2 million deaths per year worldwide. Also, agents that reduce the duration and complexity of the current therapy would have a major impact on the overall cure rate. Due to the development of resistance to conventional antibiotics there is a need for new therapeutic strategies to combat Mycobacterium tuberculosis. Subsequently, there is an urgent need for the development of new drug candidates with newer targets and alternative mechanism of action. In this perspective, pyrazole, one of the most important classes of heterocycles, has been the topic of research for thousands of researchers all over the world because of its wide spectrum of biological activities. To pave the way for future research, there is a need to collect the latest information in this promising area. In the present review, we have collated published reports on the pyrazole core to provide an insight so that its full therapeutic potential can be utilized for the treatment of tuberculosis. In this article, the possible structure-activity relationship of pyrazole analogs for designing better antituberculosis (anti-TB) agents has been discussed and is also helpful for new thoughts in the quest for rational designs of more active and less toxic pyrazole-based anti-TB drugs.

Synthesis, characterization and pharmacological screening of some novel 5-imidazopyrazole incorporated polyhydroquinoline derivatives

A new category of polyhydroquinoline derivatives 8a-t were synthesized in moderate to good yield (64-85%) by one-pot three-component cyclocondensation reaction of 5-(1H-imidazol-1-yl)-3-methyl-1-phenyl-1H-pyrazole-4-carbaldehyde 3 with various enaminones 6a-h and different active methylene compounds (malononitrile 7a, ethylcaynoacetate 7b and caynoacetamide 7c) in absolute ethanol. The newly synthesized compounds were evaluated for their in vitro antimalarial activity against Plasmodium falciparum, in vitro antibacterial activity against a panel of pathogenic strains of bacteria and fungi and also for their antitubercular activity against Mycobacterium tuberculosis H37Rv strain. Two of them (8n, 8t) exhibited excellent antimalarial activity. Some of them exhibited excellent antibacterial activity and moderate antituberculosis activity compared with the first line drugs.

Synthesis, structure-activity relationships, and in vitro antibacterial and antifungal activity evaluations of novel pyrazole carboxylic and dicarboxylic acid derivatives

A series of pyrazole-3-carboxylic acid and pyrazole-3,4-dicarboxylic acid derivatives were synthesized, the structures were confirmed by their NMR ((1)H and (13)C) and FT-IR spectra, and elemental analyses. The antibacterial and antifungal activities of the compounds against five bacterial and five fungal pathogens were screened using modified agar well diffusion assay. Most of the molecules have inhibitory effects on both standard and clinical Candida albicans strains. However, only the molecules 8, 10, 21, and 22 demonstrate some inhibitory effects on Candida parapsilosis, Candida tropicalis, and Candida glabrata strains. The structure-antifungal activity relationships of the compounds on the C. albicans strains were investigated by electron-conformational method. The pharmacophores and antipharmacophores responsible for the inhibition and non-inhibition of the C. albicans strains were obtained by electronic and geometrical characteristics of the reactive fragments of the molecules. These fragments along with the associated parameters can be used in designing the future more potent antifungal agents. It has been shown that both the positions of electronegative atoms like F and O in the pyrazole substituents and the amount of the associated charges on such atoms are crucial in regulating the strength of antifungal activity for the C. albicans strain.

Design, synthesis, characterization and anti-inflammatory evaluation of novel pyrazole amalgamated flavones

A series of novel pyrazole amalgamated flavones has been designed and synthesized from 1-methyl-5-(2,4,6-trimethoxy-phenyl)-1H-pyrazole 6. The structures of regioisomers 6 and 7 were resolved by 2D (1)H-(1)H COSY, (1)H-(13)C HSQC and (1)H-(13)C HMBC experiments. The newly synthesized compounds were tested for their in vitro COX inhibition and in vivo carrageenan induced hind paw edema in rats and acetic acid induced vascular permeability in mice. Although the compounds have inhibitory profile against both COX-1 and COX-2, some of the compounds are found to be selective against COX-2, supported by inhibition of paw edema and vascular permeability. Docking studies were also carried out to determine the structural features which sway the anti-inflammatory activity of the tested compounds. The keto and phenolic -OH are major factors that are prominently involved in interaction with COX-2 active site.

Design, synthesis, characterization and biological evaluation of novel pyrazole integrated benzophenones

A series of novel pyrazole integrated benzophenones (9a-j) have been designed, synthesized from 1-methyl-5-(2,4,6-trimethoxy-phenyl)-1H-pyrazole 6. The structures of the regioisomers 6 and 7 were determined by 2D (1)H-(1)H COSY, (1)H-(13)C HSQC and (1)H-(13)C HMBC experiments. The newly synthesized compounds (9a-j) were evaluated for in vivo anti-inflammatory activity by carrageenan paw edema in rats and in vitro COX-1/COX-2 inhibition and antioxidant potential. Among the synthesized compounds, compounds 9b, 9d and 9f, were found to be active anti-inflammatory agents in addition to having potent antioxidant activity.

Synthesis of methyl pyropheophorbide-a pyrazole derivatives and their in vitro cell viabilities on A549 cells

Porphyrins and chlorins containing acetylacetone residues on the peripheral substituents are known to readily react with hydrazine derivatives to form porphyrin and chlorin derivatives possessing a pyrazole moiety. In this study, we have carried out the synthesis of methyl pyropheophorbide-a derivatives containing a pyrazole moiety on its peripheral position. Moreover, we have examined a preliminary in vitro effect of these new derivatives on A549 cancer cell in photodynamic therapy.

Synthesis and antimicrobial activities of novel 1,5-diaryl pyrazoles

Novel 1,5-diaryl pyrazole derivatives viz. 5-(4-chlorophenyl)-1-(4-fluorophenyl)-1H-pyrazole-3-carboxamides (2a-e, 3, 3a-f), 2-(5-(4-chlorophenyl)-1-(4-fluorophenyl)-1H-pyrazole-3-yl)thiazoles (6a-c,7, 8, 9a-c, 10, 11) were synthesized by varying the active part (amide group) of pyrazole, characterized using IR, (1)H NMR, mass spectral data and screened for their antibacterial activity against Escherichia coli (ATTC-25922), Staphylococcus aureus (ATTC-25923), Pseudomonas aeruginosa (ATTC-27853), Klebsiella pneumonia. Similarly all these compounds were screened for their antifungal activity against Aspergillus flavus (NCIM No. 524), Aspergillus fumigates (NCIM No. 902), Penicillium marneffei and Trichophyton mentagrophytes. Interestingly all the synthesized compounds exhibited good antibacterial (except 2a-c, 8, 9a) and antifungal activity (except 2a-c, 6a, 8, 9a).

Synthesis and in vitro antitumor evaluation of some indeno[1,2-c]pyrazol(in)es substituted with sulfonamide, sulfonylurea(-thiourea) pharmacophores, and some derived thiazole ring systems

The synthesis of a series of 3-(4-chlorophenyl)-[1,2-c]pyrazol(in)es substituted with benzenesulfonamide, N1,N3-disubstituted sulfonylurea, sulfonylthiourea pharmacophores, and some derived thiazolidinone and thiazoline ring systems is described. All the newly synthesized target compounds were subjected to the NCI-in vitro disease-oriented antitumor screening to be evaluated for their antitumor activity. Eight compounds namely; 2-4, 7, 8, 10, 13, and 16; showed promising broad spectrum antitumor activity against most of the tested subpanel tumor cell lines (GI50 < 100 microM). Compound 3, 4-(3-(4-chlorophenyl)-4H-indeno[1,2-c]pyrazol- 2-yl)-benzenesulfonamide; although it did not show the highest growth inhibitory value (GI50 (MG-MID) 13.2 microM), it proved to be the most active analog in this study with the highest cytostatic and cytotoxic potentials (TGI and LC50 (MG-MID) concentrations of 33.1 and 66.1 microM, respectively). In general, the oxidized pyrazoles displayed better antitumor activity than their parent pyrazoline analogs, whereas the benzenesulfonamides and the N1, N3-disubstituted sulfonylureas showed significant better antitumor spectrum than the sulfonylthioureido and the derived thiazole analogs.

Antileishmanial and Antibacterial Activity of a New Pyrazole Derivative Designated 4-[2-(1-(Ethylamino)-2-methyl- propyl)phenyl]-3-(4-methyphenyl)-1-phenylpyrazole

Here, we report for the first time the synthesis and the antileishmanial activity of a new pyrazole derivative, namely 4-[2-(1-(ethylamino)-2-methylpropyl)phenyl]-3-(4-methyphenyl)-1-phenylpyrazole). Micromolar concentrations of this compound were found to inhibit the in vitro multiplication of Leishmania tropica, Leishmania major, and Leishmania infantum, three species causing different forms of leishmaniasis. Furthermore, the 50% inhibitory concentration (IC50) values for the compound are only slightly higher than those of amphotericin B, one of the most active antileishmanial agents used as a satisfactory substitute in cases not responding to pentostam. The IC50 values after 48 h for L. tropica, L. major, and L. infantum promastigote growth were 0.48 microg/mL, 0.63 microg/mL and 0.40 microg/mL, respectively for the compound, while they were 0.23 microg/mL, 0.29 microg/mL and 0.24 microg/mL, respectively for amphotericin B. We also tested this compound for its antibacterial activity against several bacteria. The strongest antibacterial activity was observed against Entrococcus feacalis and Staphylococcus aureus with a minimal inhibitory concentration (MIC) of 60 microg/mL.

Amidrazones as Precursors of Biologically Active Compounds - Synthesis of Diaminopyrazoles for Evaluation of Anticancer Activity

The regioselectivity of coupling phenyl isocyanate to 3-(2-acylhydrazino)-3-aminopropenenitriles and ethyl 3-(2-acylhydrazino)-3-aminopropenoates as simple access to aminopyrazole derivatives, endowed with potential antitumoral activity, is reported. 3-(2-Acylhydrazino)-3-aminopropenenitriles react with phenyl isocyanate to afford 3-amino-3-(2-acylhydrazino)-2-phenylaminocarbonyl-2-propenenitriles. These key intermediates were cyclized into 3,5-diaminopyrazole-4-carboxamide derivatives. Preliminary results of poor antiproliferative activities of these compounds are also reported.

New trends in synthesis of pyrazole nucleosides as new antimetabolites

Pyrazole nucleosides and condensed pyrazole nucleosides exhibit various biological activities. This article describes recent synthetic approaches to their preparation, chemical properties, biological activities, and structure-activity relationships, with emphasis to selected drugs or drug candidates. Two pyrazole C-nucleoside compounds pyrazofurin (pyrazomycin) and its alpha-epimer pyrazofurin B are active components of potent antivirals approved for therapeutic use in human medicine aimed against various diseases caused by DNA viruses.