Synthesis and Characterization of New 3-(4-Arylpiperazin-1-yl)-2-hydroxypropyl 4-Propoxybenzoates and Their Hydrochloride Salts

Indol-2-Carboxylic Acid Esters Containing N-Phenylpiperazine Moiety - Preparation and Cholinesterase-inhibiting Activity

BACKGROUND

The indole derivatives and the N-phenylpiperazine fragment represent interesting molecular moieties suitable for the research of new potentially biologically active compounds. This study was undertaken to identify if indol-2-carboxylic acid esters containing N-phenylpiperazine moiety possess acetylcholinesterase and butyrylcholinesterase inhibitory activity.

MATERIALS AND METHODS

The study dealt with the synthesis of a novel series of analogs of 1H-indole-2- carboxylic acid and 3-methyl-1H-indole-2-carboxylic acid. The structure of the derivatives was represented by the indolylcarbonyloxyaminopropanol skeleton with the attached N-phenylpiperazine or diethylamine moiety, which formed a basic part of the molecule. The final products were synthesized as dihydrochloride salts, fumaric acid salts, and quaternary ammonium salts. The first step of the synthetic pathway led to the preparation of esters of 1H-indole-2-carboxylic acid from the commercially available 1H-indole-2-carboxylic acid. The Fischer indole synthesis was used to synthesize derivatives of 3-methyl-1H-indole-2-carboxylic acid.

RESULTS AND DISCUSSION

Final 18 indolylcarbonyloxyaminopropanols in the form of dihydrochlorides, fumarates, and quaternary ammonium salts were prepared using various optimization ways. The very efficient way for the formation of 3-methyl-1H-indole-2-carboxylate (Fischer indole cyclization product) was the one-pot synthesis of phenylhydrazine with methyl 2-oxobutanoate with acetic acid and sulphuric acid as catalysts.

CONCLUSION

Most of the derivatives comprised of an attached N-phenylpiperazine group, which formed a basic part of the molecule and in which the phenyl ring was substituted in position C-2 or C-4. The synthesized compounds were subjected to cholinesterase-inhibiting activity evaluation, by modified Ellman method. Quaternary ammonium salt of 1H-indole-2-carboxylic acid which contain N-phenylpiperazine fragment with nitro group in position C-4 (7c) demonstrated the most potent activity against acetylcholinesterase.

Development of Pelubiprofen Tromethamine with Improved Gastrointestinal Safety and Absorption

Pelubiprofen (PEL), which is a commercialized non-steroidal anti-inflammatory drug (NSAID), is associated with the risk of gastrointestinal (GI) adverse events following long-term exposure and has poor water-soluble properties. Here, a new pelubiprofen tromethamine (PEL-T) with improved solubility, permeability, GI safety, and absorption, compared to PEL, has been developed. The nuclear magnetic resonance spectroscopy (NMR), differential scanning calorimetry (DSC), and Fourier transform infrared spectroscopy (FT-IR) results confirmed that the PEL-T was well formed. The powder of PEL-T showed the presence of additional 6H protons at δ 3.66-3.61 in the ¹H NMR spectrum, and shifted the sharp endothermic peaks at 129 °C in DSC, and the spectrum of distinct absorption peaks in FT-IR. In addition, compared with PEL, PEL-T showed a significantly improved solubility in various media and an increased permeability coefficient (K_p) in Caco-2 cells. Furthermore, compared to PEL oral administration, PEL-T was found to significantly reduce the damaged area in an acute gastric damage rat model. The pharmacokinetic study of the PEL-T powder showed higher maximum plasma concentration (C_max) and area under the plasma concentration-time curve from 0 h to the last time point (AUC_t) than those of the PEL powder. Taken together, our data suggest that PEL-T is a recommendable candidate with enhanced gastrointestinal safety and better absorption compared with commercial PEL.

Hydroxynaphthalenecarboxamides and substituted piperazinylpropandiols, two new series of BRAF inhibitors. A theoretical and experimental study

The oncogenic mutated kinase BRAF^V600E is an attractive molecular target because it is expressed in several human cancers, including melanoma. To present, only three BRAF small inhibitors are approved by the FDA for the treatment of patients with metastatic melanoma: Vemurafenib, Dabrafenib and Encorafenib. Although many protocol treatments have been probed in clinical trials, BRAF inhibition has a limited effectiveness because patients invariably develop resistance and secondary toxic effects associated with the therapy. These limitations highlight the importance of designing new and better inhibitors with different structures that could establish different interactions in the active site of the enzyme and therefore decrease resistance progress. Considering the data from our previous report, here we studied two series of derivatives of structural scaffolds as potential BRAF inhibitors: hydroxynaphthalenecarboxamides and substituted piperazinylpropandiols. Our results indicate that structural analogues of substituted piperazinylpropandiols do not show significantly better activities to that previously reported. In contrast, the hydroxynaphthalenecarboxamides derivatives significantly inhibited cell viability and ERK phosphorylation, a measure of BRAF activity, in Lu1205 BRAF^V600E melanoma cells. In order to better understand these experimental results, we carried out a molecular modeling study using different combined techniques: docking, MD simulations and quantum theory of atoms in molecules (QTAIM) calculations. Thus, by using this approach we determined that the molecular interactions that stabilize the different molecular complexes are closely related to Vemurafenib, a well-documented BRAF inhibitor. Furthermore, we found that bi-substituted compounds may interact more strongly respect to the mono-substituted analogues, by establishing additional interactions with the DFG-loop at the BRAF-active site. On the bases of these results we synthesized and tested a new series of hydroxynaphthalenecarboxamides bi-substituted. Remarkably, all these compounds displayed significant inhibitory effects on the bioassays performed. Thus, the structural information reported here is important for the design of new BRAF^V600E inhibitors possessing this type of structural scaffold.

Activity of N-Phenylpiperazine Derivatives Against Bacterial and Fungal Pathogens

BACKGROUND

As the bacterial resistance to antibacterial chemotherapeutics is one of the greatest problems in modern medicine, efforts are made to develop new antimicrobial drugs. Compounds with a piperazine ring have proved to be promising agents against various pathogens.

OBJECTIVE

The aim of the study was to prepare a series of new N-phenylpiperazines and determine their activity against various pathogens.

METHOD

Target compounds were prepared by multi-step synthesis starting from an appropriate substituted acid to an oxirane intermediate reacting with 1-(4-nitrophenyl)piperazine. Lipophilicity and pKa values were experimentally determined. Other molecular parameters were calculated. The inhibitory activity of the target compounds against Staphylococcus aureus, four mycobacteria strains, Bipolaris sorokiniana, and Fusarium avenaceum was tested. In vitro antiproliferative activity was determined on a THP-1 cell line, and toxicity against plant was determined using Nicotiana tabacum.

RESULTS

In general, most compounds demonstrated only moderate effects. 1-(2-Hydroxy-3-{[4-(propan- 2-yloxy)benzoyl]oxy}propyl)-4-(4-nitrophenyl)piperazinediium dichloride and 1-{3-[(4-butoxybenzoyl)- oxy]-2-hydroxypropyl}-4-(4-nitrophenyl)piperazinediium dichloride showed the highest inhibition activity against M. kansasii (MIC = 15.4 and 15.0 µM, respectively) and the latter also against M. marinum (MIC = 15.0 µM). 1-(2-Hydroxy-3-{[4-(2-propoxyethoxy)benzoyl]oxy}propyl)-4-(4-nitrophenyl)piperazinediium dichloride had the highest activity against F. avenaceum (MIC = 14.2 µM). All the compounds showed only insignificant toxic effects on human and plant cells.

CONCLUSION

Ten new 1-(4-nitrophenyl)piperazine derivatives were prepared and analyzed, and their antistaphylococcal, antimycobacterial, and antifungal activities were determined. The activity against M. kansasii was positively influenced by higher lipophilicity, the electron-donor properties of substituent R and a lower dissociation constant. The exact mechanism of action will be investigated in follow-up studies.

An integrative study to identify novel scaffolds for sphingosine kinase 1 inhibitors

Sphingosine kinase 1 (SphK1), the enzyme that produces the bioactive sphingolipid metabolite, sphingosine-1-phosphate, is a promising new molecular target for therapeutic intervention in cancer and inflammatory diseases. In view of its importance, the main objective of this work was to find new and more potent inhibitors for this enzyme possessing different structural scaffolds than those of the known inhibitors. Our theoretical and experimental study has allowed us to identify two new structural scaffolds (three new compounds), which could be used as starting structures for the design and then the development of new inhibitors of SphK1. Our study was carried out in different steps: virtual screening, synthesis, bioassays and molecular modelling. From our results, we propose a new dihydrobenzo[b]pyrimido[5,4-f]azepine and two alkyl{3-/4-[1-hydroxy-2-(4-arylpiperazin-1-yl)ethyl]phenyl}carbamates as initial structures for the development of new inhibitors. In addition, our molecular modelling study using QTAIM calculations, allowed us to describe in detail the molecular interactions that stabilize the different Ligand-Receptor complexes. Such analyses indicate that the cationic head of the different compounds must be refined in order to obtain an increase in the binding affinity of these ligands.

Synthesis and Determination of Physicochemical Properties of New 3-(4-Arylpiperazin-1-yl)-2-hydroxypropyl 4-Alkoxyethoxybenzoates

Nine new dihydrochloride salts of 3-(4-arylpiperazin-1-yl)-2-hydroxypropyl 4-alkoxyethoxybenzoates were designed and synthesized. The physicochemical properties such as lipophilicity index (log k_w) and dissociation constant (pK_a) were experimentally determined and compared to the software calculated data. The lipophilicity index was determined by means of reversed-phase high performance liquid chromatography (RP-HPLC). The pK_a values were determined by means of capillary zone electrophoresis. The "drug-likeness" properties according to the Lipinski Rule of Five and prediction of possible blood-brain barrier penetration were computed and discussed.