Regioselective Synthesis, Structural Characterization, and Antiproliferative Activity of Novel Tetra-Substituted Phenylaminopyrazole Derivatives

A small library of highly functionalized phenylaminopyrazoles, bearing different substituents at position 1, 3 and 4 of the pyrazole ring, was prepared by the one pot condensation of active methylene reagents, phenylisothiocyanate and substituted hydrazine (namely, methyl- and benzyl-hydrazine). The identified reaction conditions proved to be versatile and efficient. Fur-thermore, the evaluation of alternative stepwise protocols affected the chemo- and re-gio-selectivity outcome of the one-pot procedure. The chemical identity of two N-methyl pyrazole isomers, selected as prototypes of the whole series, was unambiguously identified by means of NMR and mass spectrometry studies. Additionally, semiempirical calculations provided a structural rationale for the different chromatographic behaviour of the two isomers. The prepared tetra-substituted phenylaminopyrazoles were tested in cell-based assays on a panel of cancer and normal cell lines. The tested compounds did not show any cytotoxic effect on the selected cell lines, thus supporting their pharmaceutical potentials

Potent and Broad-Spectrum Bactericidal Activity of a Nanotechnologically Manipulated Novel Pyrazole

: The antimicrobial potency of the pyrazole nucleus is widely reported these days, and pyrazole derivatives represent excellent candidates for meeting the worldwide need for new antimicrobial compounds against multidrug-resistant (MDR) bacteria. Consequently, 3-(4-chlorophenyl)-5-(4-nitrophenylamino)-1H-pyrazole-4-carbonitrile (CR232), recently reported as a weak antiproliferative agent, was considered to this end. To overcome the CR232 water solubility issue and allow for the determination of reliable minimum inhibitory concentration values (MICs), we initially prepared water-soluble and clinically applicable CR232-loaded nanoparticles (CR232-G5K NPs), as previously reported. Here, CR232-G5K NPs have been tested on several clinically isolates of Gram-positive and Gram-negative species, including MDR strains. While for CR232 MICs 65 128 \ub5g/mL (376.8 \ub5M) were obtained, very low MICs (0.36-2.89 \ub5M) were observed for CR232-G5K NPs against all of the considered isolates, including colistin-resistant isolates of MDR Pseudomonas aeruginosa and Klebsiella pneumoniae carbapenemases (KPCs)-producing K. pneumoniae (0.72 \ub5M). Additionally, in time-kill experiments, CR232-G5K NPs displayed a rapid bactericidal activity with no significant regrowth after 24 h on all isolates tested, regardless of their difficult-to-treat resistance. Conjecturing a clinical use of CR232-G5K NPs, cytotoxicity experiments on human keratinocytes were performed, determining very favorable selectivity indices. Collectively, due to its physicochemical and biological properties, CR232-G5K NPs could represent a new potent weapon to treat infections sustained by broad spectrum MDR bacteria

Antimalarial Activity of Tri- and Tetra-Substituted Anilino Pyrazoles

Pyrazole core represents a privilege scaffold in medicinal chemistry; a number of pyrazole compounds are endowed with various pharmacological activities in different therapeutic areas including antimalarial treatment. Supported by this evidence, a series of 5-anilino-3-(hetero)arylpyrazoles were evaluated for their antiplasmodial activity in in vitro assays. The compounds were synthesized according to regioselective and versatile protocols that combine active methylene reagents, aryl isothiocyanates and (substituted)hydrazines. The considered derivatives 2 allowed the definition of consistent structure–activity relationships and compounds 2b,e,k,l were identified as the most interesting derivatives of the series showing micromolar IC50 values against chloroquine-sensitive and chloroquine-resistant Plasmodium strains. Additionally, the most active anilino-pyrazoles did not show any cytotoxicity against tumor and normal cells and were predicted to have favorable drug-like and pharmacokinetic properties

Regioselective Synthesis, Structural Characterization, and Antiproliferative Activity of Novel Tetra-Substituted Phenylaminopyrazole Derivatives

A small library of highly functionalized phenylaminopyrazoles, bearing different substituents at position 1, 3, and 4 of the pyrazole ring, was prepared by the one-pot condensation of active methylene reagents, phenylisothiocyanate, and substituted hydrazine (namely, methyl- and benzyl-hydrazine). The identified reaction conditions proved to be versatile and efficient. Furthermore, the evaluation of alternative stepwise protocols affected the chemo- and regio-selectivity outcome of the one-pot procedure. The chemical identities of two N-methyl pyrazole isomers, selected as prototypes of the whole series, were unambiguously identified by means of NMR and mass spectrometry studies. Additionally, semiempirical calculations provided a structural rationale for the different chromatographic behavior of the two isomers. The prepared tetra-substituted phenylaminopyrazoles were tested in cell-based assays on a panel of cancer and normal cell lines. The tested compounds did not show any cytotoxic effect on the selected cell lines, thus supporting their pharmaceutical potentials

Diversity-oriented synthesis of highly-functionalized amino-pyrazoles as pharmaceutically relevant compounds

The pyrazole ring represents a valuable heterocycle in medicinal chemistry, being shared by several effective molecules with a broad range of activity. In particular, amino-pyrazoles constitute a versatile framework in drug discovery. By taking advantage of our expertise on the condensation of active methylene reagents and heterocumulenes, we developed new synthetic strategies for the preparation of highly-functionalized amino-pyrazoles through the formation of ketene N,S- or S,S-acetals. A One-pot synthetic procedure led to the formation of a series of pyrazole compounds endowed with promising antiproliferative activity in cell-based assay. Docking simulations carried out on the most active molecules indicated estrogen receptors as a potential target inside the cell. Alongside, a stepwise synthetic protocol was used to prepare novel antioxidant pyrazole hydrazones that efficiently inhibited reactive oxygen species (ROS) formation and platelet aggregation. The same synthetic approach allowed the preparation of amino-pyrazoles with interesting antiangiogenetic properties as assessed in wound healing and tube formation assays on human fibroblasts and endothelial cells. Furthermore, these compounds displayed good Akt phosphorylation inhibition in Western Blot analyses. Based on literature data, a set of pyrazoles was tested as antimalarial agents against D10 Chloroquine(CQ)-sensitive and W2 CQ-resistant P. falciparum strains. Selected derivatives showed micromolar IC50 values against the two considered protozoa strains and further SAR extension studies led to the identification of novel amino-pyrazole and pyrazolopyrimidine derivatives with improved antimalarial properties especially against the CQ-resistant W2 strain. Overall, the development of diversity-oriented procedures for the preparation of highly substituted pyrazoles allowed the identification of unreported hit compounds as antiproliferative, antiangiogenic, antioxidant and antimalarial agents and provide further support to the pharmaceutical potential of pyrazole nucleus and heterocyclic system thereof derived in different therapeutic areas

AMINO-PYRAZOLES: A PRIVILEGED SCAFFOLD FOR THE SYNTHESIS OF BIOLOGICALLY ACTIVE COMPOUNDS

Taking as lead structures previous reported pyrazoles, we designed and synthesized novel series of pyrazoles 2-5. All the isolated molecules were prepared by a stepwise protocol that allowed the preparation of N,S-thioketal intermediates which were then condensed with the proper hydrazine. Pyrazole hydrazones 3 displayed good antiproliferative and antioxidant activity, APs 4 exhibited significant antiangiogenetic properties and anilino-pyrazoles 5 showed antimalarial activity in the micromolar range. Overall, these results further support the pharmaceutical potential of amino pyrazoles in different therapeutic areas

Amino-Pyrazoles in Medicinal Chemistry: A Review

A pyrazole nucleus is an easy-to-prepare scaffold with large therapeutic potential. Consequently, the search for new pyrazole-based compounds is of great interest to the academic community as well as industry. In the last ten years, a large number of papers and reviews on the design, synthesis, and biological evaluation of different classes of pyrazoles and many pyrazole-containing compounds have been published. However, an overview of pyrazole derivatives bearing a free amino group at the 3, 4, or 5 position (namely, 3-aminopyrazoles, 4-aminopyrazoles, and 5-aminopyrazoles, respectively) and their biological properties is still missing, despite the fact that aminopyrazoles are advantageous frameworks able to provide useful ligands for receptors or enzymes, such as p38MAPK, and different kinases, COX and others, as well as targets important for bacterial and virus infections. With the aim to fill this gap, the present review focuses on aminopyrazole-based compounds studied as active agents in different therapeutic areas, with particular attention on the design and structure-activity relationships defined by each class of compounds. In particular, the most relevant results have been obtained for anticancer/anti-inflammatory compounds, as the recent approval of Pirtobrutinib demonstrates. The data reported here are collected from different databases (Scifinder, Web of Science, Scopus, Google Scholar, and Pubmed) using “aminopyrazole” as the keyword

HIGHLY-FUNCTIONALIZED AMINO PYRAZOLES AS ANTIOXIDANT AGENTS: A PRELIMINARY SYNTHETIC ACCESSIBILITY STUDY

5-pyrazolyl urea derivatives showed interesting pharmaceutical properties. In particular, compounds 1 (Figure 1) showed promising antioxidant activity by inhibiting ROS formation in platelet. The free amino group on the pyrazole ring appear to be essential for the antioxidant activity whereas the substitution of the catechol moiety (X group, Figure 1) modulate the ability of the compound to block ROS formation. To further extend the SARs of derivatives 1 and evaluate the effect on the activity of the introduction of a N-phenyl substituent on the pyrazole scaffold, we planned the synthesis of new amino pyrazoles 2 (Figure 1). In order to assess the chemical accessibility to the desired compounds, synthetic path A and B (Scheme 1) were considered. Methylhydrazine and p-anisaldehyde were selected as template reagents. Despite literature data, path A proved to be ineffective as the cyclization reaction could not occur in a number of different experimental conditions. Path B led to the isolation of the desired compound as a mixture of the two possible N-methyl isomers in good yields. In the poster, the different synthetic conditions as well as the characterization of the obtained pyrazole isomers will be presented

Successful Dendrimer and Liposome-Based Strategies to Solubilize an Antiproliferative Pyrazole Otherwise Not Clinically Applicable

Water-soluble formulations of the pyrazole derivative 3-(4-chlorophenyl)-5-(4-nitrophenylamino)-1H-pyrazole-4-carbonitrile (CR232), which were proven to have in vitro antiproliferative effects on different cancer cell lines, were prepared by two diverse nanotechnological approaches. Importantly, without using harmful organic solvents or additives potentially toxic to humans, CR232 was firstly entrapped in a biodegradable fifth-generation dendrimer containing lysine (G5K). CR232-G5K nanoparticles (CR232-G5K NPs) were obtained with high loading (DL%) and encapsulation efficiency (EE%), which showed a complex but quantitative release profile governed by Weibull kinetics. Secondly, starting from hydrogenated soy phosphatidylcholine and cholesterol, we prepared biocompatible CR232-loaded liposomes (CR232-SUVs), which displayed DL% and EE% values increasing with the increase in the lipids/CR232 ratio initially adopted and showed a constant prolonged release profile ruled by zero-order kinetics. When relevant, attenuated total reflectance Fourier transformed infrared spectroscopy (ATR-FTIR) and nuclear magnetic resonance (NMR) spectroscopy, scanning electron microscopy (SEM) and dynamic light scattering (DLS) experiments, as well as potentiometric titrations completed the characterization of the prepared NPs. CR232-G5K NPs were 2311-fold more water-soluble than the pristine CR232, and the CR232-SUVs with the highest DL% were 1764-fold more soluble than the untreated CR232, thus establishing the success of both our strategies

PDE4D: A Multipurpose Pharmacological Target

Phosphodiesterase 4 (PDE4) enzymes catalyze cyclic adenosine monophosphate (cAMP) hydrolysis and are involved in a variety of physiological processes, including brain function, monocyte and macrophage activation, and neutrophil infiltration. Among different PDE4 isoforms, Phosphodiesterases 4D (PDE4Ds) play a fundamental role in cognitive, learning and memory consolidation processes and cancer development. Selective PDE4D inhibitors (PDE4Dis) could represent an innovative and valid therapeutic strategy for the treatment of various neurodegenerative diseases, such as Alzheimer's, Parkinson's, Huntington's, and Lou Gehrig's diseases, but also for stroke, traumatic brain and spinal cord injury, mild cognitive impairment, and all demyelinating diseases such as multiple sclerosis. In addition, small molecules able to block PDE4D isoforms have been recently studied for the treatment of specific cancer types, particularly hepatocellular carcinoma and breast cancer. This review overviews the PDE4DIsso far identified and provides useful information, from a medicinal chemistry point of view, for the development of a novel series of compounds with improved pharmacological properties