N-substituted Piperazine Research Articles

Novel Piperazine Derivatives of Vindoline as Anticancer Agents.

A series of novel vindoline-piperazine conjugates were synthesized by coupling 6 N-substituted piperazine pharmacophores at positions 10 and 17 of Vinca alkaloid monomer vindoline through different types of linkers. The in vitro antiproliferative activity of the 17 new conjugates was investigated on 60 human tumor cell lines (NCI60). Nine compounds presented significant antiproliferative effects. The most potent derivatives showed low micromolar growth inhibition (GI50) values against most of the cell lines. Among them, conjugates containing [4-(trifluoromethyl)benzyl]piperazine (23) and 1-bis(4-fluorophenyl)methyl piperazine (25) in position 17 of vindoline were outstanding. The first one was the most effective on the breast cancer MDA-MB-468 cell line (GI50 = 1.00 μM), while the second one was the most effective on the non-small cell lung cancer cell line HOP-92 (GI50 = 1.35 μM). The CellTiter-Glo Luminescent Cell Viability Assay was performed with conjugates 20, 23, and 25 on non-tumor Chinese hamster ovary (CHO) cells to determine the selectivity of the conjugates for cancer cells. These compounds exhibited promising selectivity with estimated half-maximal inhibitory concentration (IC50) values of 2.54 μM, 10.8 μM, and 6.64 μM, respectively. The obtained results may have an impact on the design of novel vindoline-based anticancer compounds.

Dihydrobenzothiazole coupled N-piperazinyl acetamides as antimicrobial agents: Design, synthesis, biological evaluation and molecular docking studies.

Substituted saturated N-heterocycles have gained momentum as effective scaffolds for the development of new drugs. In this study, we coupled partly saturated benzothiazoles with substituted piperazines and evaluated their antimicrobial activity. Following a three-step reaction sequence from commercially available cyclic 1,3-diones, a series of novel 2-[4-substituted-1-piperazinyl]-N-(7-oxo-4,5,6,7-tetrahydrobenzo[d]thiazol-2-yl)acetamides (7a-af) were synthesised. 2-Amino-5,6-dihydro-benzo[d]thiazol-7(4H)-ones, obtained through the condensation of cyclohexane-1,3-diones with thiourea, were acetylated with chloroacetic chloride and then reacted with N-substituted piperazines 6a-p to give the desired products 7a-af in excellent yields. All 32 new compounds were fully characterised by their 1 H-nuclear magnetic resonance (NMR), 13 C-NMR and high-resolution mass spectrometry spectra. The synthetic compounds 7a-af were tested in vitro for their efficacy as antimicrobials against pathogenic strains of Gram-positive and Gram-negative bacteria, Streptococcus mutans and Salmonella typhi, respectively, as well as against fungal strains, including Candida albicans 3018 and C. albicans 4748. Ciprofloxacin and fluconazole served as the reference drugs. While compounds 7c and 7l showed inhibition against fungal strains with zones of inhibition of 11 and 1 mm, respectively, four analogues (7d, 7l, 7n, and 7r) demonstrated strong antibacterial action (zone of inhibition in the range of 10-15 mm). Three compounds (7j, 7l, and 7w) also exhibited moderate antitubercular activity (MIC: 6.25 µg/mL) against Mycobacterium tuberculosis H37Rv. Molecular docking investigations and the predicted physicochemical and ADMET (absorption, distribution, metabolism, excretion, and toxicity) properties for the potent compounds made this scaffold useful as a pharmacologically active framework for the development of potential antimicrobial hits.

Design, Synthesis of Novel N-Substituted 6α-Piperazinomethyl-Δ4-3,17-diketosteroids and their Antimicrobial Activity Evaluation

Abstract: This report presents the synthesis of three innovative N-substituted 6α- piperazinomethyl-Δ4-3,17-diketo-steroids via the region-directed three-component condensation method. The compounds were produced from N-substituted piperazine derivatives and androst- 4-en-3,17-dione (AD). Comprehensive physicochemical methods of analysis were employed to characterize the synthesized products. The study involved antibacterial testing of the synthesized compounds against Escherichia coli ATCC 25922, Bacillus subtilis ATCC 6633, and Staphylococcus aureus 209P FDA, with a comparison to the amoxicillin/clavulanic acid composition. It further assessed antifungal activity against Aspergillus niger INA 00760, with results compared to amphotericin B and nystatin. Initial assessment of the antibacterial and antifungal activities exhibited by the synthesized compounds suggests that this series of N-substituted 6α-piperazinomethyl-Δ4-3,17- diketo-steroids holds great potential for further biological investigation.

Iridium-Catalyzed Regio- and Diastereoselective Synthesis of C-Substituted Piperazines.

Piperazine rings are essential motifs frequently found in commercial drugs. However, synthetic methodologies are mainly limited to N-substituted piperazines, preventing structural diversity. Disclosed herein is a straightforward catalytic method for the synthesis of complex C-substituted piperazines based on an uncommon head-to-head coupling of easily prepared imines. This 100% atom-economic process allows the selective formation of a sole diastereoisomer, a broad substrate scope, and a good functional group tolerance employing a bench-stable iridium catalyst under mild reaction conditions. Key to the success is the addition of N-oxides to the reaction mixture, as they notably enhance the catalytic activity and selectivity.

DFT-based computations on some structurally related N-substituted piperazines

In order to focus on more promising drug candidates by reducing the failures that occur in the time-consuming and expensive discovery process of new drugs, it is highly efficient to predict the bioactivity and metabolism behaviors of drug candidates using computational chemistry methods. In this context, this study presents a comparative quantum chemical analysis of the buspirone, used in the treatment of anxiety, and its three structurally related derivatives, kaspar, mesmar, and gepirone, based on Density Functional Theory (DFT) calculations. Geometry optimization and frequency calculations of each molecule were implemented at B3LYP/6–31G (d, p) and B3LYP/6–311++G (d, p) levels of theory. Linear correlation coefficients (R2) were calculated for each piperazine derivative to detect the power of the relationship between theoretical and experimental structural parameters. Subsequently, frontier molecular orbital (FMO) analysis, quantum chemical reactivity descriptors, electrostatic surface properties (ESP), and natural bond orbital (NBO) analysis were examined in detail. The lipophilicity evaluations of mentioned piperazine derivatives were interpreted not only according to the data obtained from the DFT calculations, but also according to the results obtained from the Molinspiration software. As a result of both methods, the order of lipophilicity emerged as kaspar > mesmar > buspirone > gepirone. It is revealed that on account of the substitution of the pyrimidine ring in buspirone and gepirone with the quinoline ring, both lipophilicity increased and the direction of the lipophilic interaction predominantly changed. Based on all the obtained results, it is concluded that although the studied molecules are structurally very similar, they support different lipophilic interactions. Therefore, their pharmacological activities differ.

Synthesis of a library of 2-aryl-2H-tetrazole-5-carboxamides for photoaffinity labeling of aminergic G-protein coupled receptors

A four-step approach to 2-aryl-2H-tetrazole-5-carboxamides bearing GPCR-focused N-substituted piperazine residues involves ‘SAFE’ diazotransfer onto 1-(piperazin-1-yl)butane-1,3-diones followed by [3+2] cycloaddition of arenediazonium cations at the intermediate ααα-diazo acetamides. The compounds prepared are intended for photoaffinity labeling of aminergic G-protein coupled receptors.

Psychedelic-like Properties of Quipazine and Its Structural Analogues in Mice.

Known classic psychedelic serotonin 2A receptor (5-HT2AR) agonists retain a tryptamine or phenethylamine at their structural core. However, activation of the 5-HT2AR can be elicited by drugs lacking these fundamental scaffolds. Such is the case of the N-substituted piperazine quipazine. Here, we show that quipazine bound to and activated 5-HT2AR as measured by [3H]ketanserin binding displacement, Ca2+ mobilization, and accumulation of the canonical Gq/11 signaling pathway mediator inositol monophosphate (IP1) in vitro and in vivo. Additionally, quipazine induced via 5-HT2AR an expression pattern of immediate early genes (IEG) in the mouse somatosensory cortex consistent with that of classic psychedelics. In the mouse head-twitch response (HTR) model of psychedelic-like action, quipazine produced a lasting effect with high maximal responses during the peak effect that were successfully blocked by the 5-HT2AR antagonist M100907 and absent in 5-HT2AR knockout (KO) mice. The acute effect of quipazine on HTR appeared to be unaffected by serotonin depletion and was independent from 5-HT3R activation. Interestingly, some of these features were shared by its deaza bioisostere 2-NP, but not by other closely related piperazine congeners, suggesting that quipazine might represent a distinct cluster within the family of psychoactive piperazines. Together, our results add to the mounting evidence that quipazine's profile matches that of classic psychedelic 5-HT2AR agonists at cellular signaling and behavioral pharmacology levels.

N-Substituted piperazine derivatives as potential multitarget agents acting on histamine H3 receptor and cancer resistance proteins

Taking into account that multidrug resistance (MDR) is the main cause for chemotherapeutic failure in cancer treatment, the ability of novel histamine H3 receptor ligands to reverse the cancer MDR was evaluated, using the ABCB1 efflux pump inhibition assay in mouse MDR T-lymphoma cells. The most active compounds displayed significant cytotoxic and antiproliferative effects as well as a very potent MDR efflux pump inhibitory action, 3–5-fold stronger than that of reference inhibitor verapamil. Although these compounds possess weak antagonistic properties against histamine H3 receptors, they are valuable pharmacological tools in the search for novel anticancer molecules. Furthermore, for the most active compounds, an insight into mechanisms of action using either, the luminescent Pgp-Glo™ Assay in vitro or docking studies to human Pgp, was performed.

Unravelling the anticancer potential of functionalized chromeno[2,3-b]pyridines for breast cancer treatment.

A selection of new chromeno[2,3-b]pyridines was prepared from chromenylacrylonitriles and N-substituted piperazines, using a novel and efficient synthetic procedure. The compounds were tested for their anticancer activity using breast cancer cell lines MCF-7, Hs578t and MDA-MB-231 and the non-neoplastic cell line MCF-10A for toxicity evaluation. In general, compounds showed higher activity towards the luminal breast cancer subtype (MCF-7), competitive with the reference compound Doxorubicin. The in vivo toxicity assay using C. elegans demonstrated a safe profile for the most active compounds. Chromene 3f revealed a promising drug profile, inhibiting cell growth and proliferation, inducing cell cycle arrest in G2/M phase, apoptosis and microtubule destabilization. The new compounds presented exciting bioactive features and may be used as lead compounds in cancer related drug discovery.

A Novel Fluorescent Analog of the Dopamine Reuptake Inhibitor GBR12909

Dopamine transporter is a transmembrane protein associated with regulation of dopaminergic signal transmission by dopamine reuptake from the synaptic cleft back into cytosol. Some neurological disorders, for example Parkinson’s disease, are characterized by dopaminergic neuron degeneration resulting in dopamine level decrease in synapses. Therefore, dopamine transporter may be considered as a potential target in therapy of neurodegenerative disorders. However, the development of molecular tools based on dopamine transporter inhibitors remains challenging, as there is a lack of knowledge about dopamine transporter regulation and distribution in the brain. The sets of tropane and piperazine derivatives synthesized previously are the most common compounds among a number of dopamine reuptake inhibitors. It should be noted that the highest affinity and selectivity to dopamine transporter (compared with serotonin and norepinephrine ones) were demonstrated by an N-substituted piperazine derivative GBR12909. As GBR12909 has high affinity and selectivity, its structure may serve as a base for the development of novel functionalized derivatives. Design of a new fluorescent derivative based on the structure of dopamine transporter antagonist GBR12909 to investigate the transporter localization and dynamics in presynaptic membrane is the aim of this paper. We synthesized a novel fluorescent analog of dopamine transporter derivative GBR12909 labeled by the BODIPY-FL fluorophore. In order to synthesize this compound, a module synthesis scheme was developed. According to this scheme, the basic scaffold contains a linker fragment with protected amino group on the distal end of the molecule. Such scheme allows us to synthesize a set of variable GBR12909 derivatives through conjugation of various functionally significant fragments at the amino group. The first step of the target compound synthesis includes production of 1-(2-(bis(4-fluorophenyl)methoxy)ethyl)piperazine and tert-butyl(6-((4-(3-iodopropyl)phenyl)amino)-6-oxohexyl)carbamate) followed by their ‘assembly’ into one molecule. After the deprotection of the amino group, it was acylated by fluorescent BODIPY-FL-C3 acid. The fluorescent analog was used to investigate its internalization in an experiment with the PC12 pheochromocytoma cells expressing dopamine transporter. Specific accumulation of the fluorescent analog by the cells via the dopamine transporter was demonstrated, the transporter was rather sensitive to GBR12909 inhibition.

Synthesis, characterization and in vitro biological studies of novel Nitrilo derivatives of N-substituted phenyl piperazine

Synthesis, characterization and in vitro biological studies of novel Nitrilo derivatives of N-substituted phenyl piperazine

Design and synthesis of phthalazine-based compounds as potent anticancer agents with potential antiangiogenic activity via VEGFR-2 inhibition

In the designed compounds, either a biarylamide or biarylurea moiety or an N-substituted piperazine motif was linked to position 1 of the phthalazine core. The anti-proliferative activity of the synthesised compounds revealed that eight compounds (6b, 6e, 7b, 13a, 13c, 16a, 16d and 17a) exhibited excellent broad spectrum cytotoxic activity in NCI 5-log dose assays against the full 60 cell panel with GI50 values ranging from 0.15 to 8.41 µM. Moreover, the enzymatic assessment of the synthesised compounds against VEGFR-2 tyrosine kinase showed the significant inhibitory activities of the biarylureas (12b, 12c and 13c) with IC50s of 4.4, 2.7 and 2.5 μM, respectively, and with 79.83, 72.58 and 71.6% inhibition of HUVEC at 10 μM, respectively. Additionally, compounds (7b, 13c and 16a) were found to induce cell cycle arrest at S phase boundary. Compound 7b triggered a concurrent increase in cleaved caspase-3 expression level, indicating the apoptotic-induced cell death.

Synthesis of novel morpholine, thiomorpholine and N-substituted piperazine coupled 2-(thiophen-2-yl)dihydroquinolines as potent inhibitors of Mycobacterium tuberculosis

A series of novel morpholine, thiomorpholine and N-substituted piperazine coupled 2-(thiophen-2-yl)dihydroquinolines 7a–p was designed and synthesized from 2-acetyl thiophene in six step reaction sequence involving modified Bohlmann-Rahtz and Vilsmeier-Haack-Arnold reactions as key transformations. 2-(Thiophen-2-yl)dihydroquinoline was formylated and subsequently chlorinated using DMF-POCl3. The resulting aldehyde was reduced to give an alcohol and then converted to bromide using PBr3. Further coupling of bromide with morpholine, thiomorpholine and N-substituted piperazines resulted in the desired quinolines 7a-p in very good yields. All the new derivatives 7a–p were characterized by their NMR and mass spectral analysis. In vitro screening of new compounds for antimycobacterial activity against Mycobacterium tuberculosis H37Rv (MTB), resulted in two derivatives 7f and 7p as most potent antitubercular agents (MIC:1.56 μg/mL) with lower cytotoxicity profiles.

Synthesis and Anticancer Properties of Methyl N1-(thien-4-yl)amidrazone- 3-carboxylates

Background: A variety of synthetic amidrazones are endowed with antitumor activity. Examples include N1-(thien-3-yl)amidrazone-2-carboxylates that exhibit high potency against breast cancer (MCF-7) and leukemia (K562) cell lines. These results prompted us to design and examine a new set of isomeric N1-(thienyl)amidrazone. Methods: The synthesis of the targeted N1-(thien-4-yl)amidrazone-4-carboxylates 7a-n is achieved via interaction of the appropriate (N-substituted)piperazine with nitrile imine 1,3 dipole (generated in situ from the N1-(thien-4-yl)hydrazonoyl chloride precursor by the action of NEt3). Results: Among the tested compounds 7a-n, the amidrazone (7m) incorporating N4-(pyridin-2- yl)piperazine moiety was the most active against leukemia (K562) with IC50 value of 1.02 μM. Docking studies showed that 7m binds with the oncogenic protein kinase Bcr-Abl. Noteworthy, compound 7m shows negligible cytotoxic effect on human normal fibroblast cells. Conclusion: Compound 7m could probably act as a prospective lead structure for development of new synthetic N1-(thienyl)amidrazones against leukemia (K562).

Design and synthesis of a novel series of non-nucleoside HIV-1 inhibitors bearing pyrimidine and N-substituted aromatic piperazine

A novel series of substituted piperazine-1-yl-pyrimidine derivatives were designed and synthesized as a new type of HIV-1 non-nucleoside inhibitors. Various N-substituted aromatic groups were incorporated into the piperazine ring through a simple and practical route to investigate the biological activity of these target compounds against wild-type and resistant strains of HIV-1. All of the target compounds were also evaluated as HIV-1 reverse transcriptase inhibitors in MT-4 cell cultures. The biological results showed that six of these compounds displayed inhibitory activities against the wild-type strain, among of which 7q and 7t were found to be the two most active analogues possessing EC50 values of 31.50 μM and 3.36 μM, respectively. Molecular modeling studies of 7q provide valuable information for developing new anti-HIV-1 inhibitors.

Structural characterization of β-catenin and RX-5902 binding to phospho-p68 RNA helicase by molecular dynamics simulation

Emerging implications of probable ATP-dependent RNA helicase p68 in tumorigenesis and progression makes it a discerning target for cancer therapy. Recently it has been reported that tyrosyl-phosphorylation of p68 promotes β-catenin nuclear translocation and cancer metastasis through elevating the epithelial-mesenchymal transition. Despite recent advances, the structural characterization of this interaction, mode of action and induced conformational changes remain elusive. Here, through comparative structure analysis and molecular dynamics simulation assays, we explored comparative binding pattern of phospho-p68 against β-catenin. Conversely, due to the promising therapeutic potential of p68 in blocking the invasiveness and metastasis of cancer cells, we investigated the binding of heterocyclic N-substituted piperazine derivative-RX-5902 that inhibits the binding of phospho-p68 and β-catenin. Evidently, transactivation and C-terminal helicase domains of phospho-p68 exhibited dramatic conformational alterations to assist β-catenin and RX-5902 binding. As compared to unbound phospho-p68 (56.1 Å), the residual distances between transactivation domain-Ser79 and C-terminal helicase domain-Gln555 were reduced to 34.1 Å and 31 Å upon binding to β-catenin and RX-5902, respectively. In contrast, helicase ATP-binding domain remained conformationally stable throughout simulations. Clearly, the comparative docking-for-functional analysis of phospho-p68 against RX-5902 and β-catenin uncovered a spectrum of structural linkages associated with the molecular basis of β-catenin-dependent ATPase activity. Thus the outcomes of this study may provide a platform for the rational design of specific and potent inhibitors against phospho-p68 with a special emphasis on anticancer activity.

Synthesis, physical and chemical properties of 7-methylxanthine derivatives

It is known that 8-aminosubstituted N-methylated xanthines are dipeptidyl peptidase-4 antagonists, ligands for 5-hydroxytryptamine receptors and exert diverse biological effects. Previously, it was found that the 7-alkyl-8-piperazinoxanthines exhibit diuretic, depremic, analgesic effect. Some amino derivatives of 7-metilxanthine are promising antioxidants and 8-amino-7-ethyl-3-methylxanthine detects a distinct hypoglycemic effect. The aim of this work is to provide new derivatives of 7-methylxanthine – promising bioactive compounds and to study their physical and chemical properties as a basis for further structural modification of the molecule. Materials and methods . The melting point has been determined with the help of an open capillary method with PTP-M device. Elemental analysis has been performed with the help of the instrument Elementar Vario L cube, NMR-spectra have been taken on a spectrometer Bruker SF-400 (operating frequency of 400 MHz, solvent DMSO, internal standard – TMS). Results . It is established that the heating the source of bromxantine with an excess of primary amines in a mixture of water and dioxane leads to the formation of the corresponding 8-aminosubstituted 7-ethyl-3-methylxanthine. The reaction of 8-bromo-7-ethyl-3-methylxanthine and 8-bromo-7-ethyltheophylline with the more nucleophilic N-substituted piperazine is performed in the same conditions, but requires much less time and is accompanied by the formation of the corresponding 8-N-piperazinxanthines. Taking into account the amphoteric properties of imidazole it was possible to obtain 7-ethyl-8-(midazol-1)-3-methylxanthine through the reaction in dimethylformamide in the presence of equimolar amount of NaHCO 3 . 8-(4-Tret- butoxycarbonylaminopiperidinyl-1)-7-ethyl-3-methylxanthine and 8-(4-tret-butoxycarbonylamino-1)-7-ethyltheophylline are obtained by heating equimolar amounts of original bromxanthines, 4-tret-butoxycarbonylaminopiperidine and NaHCO 3 . The structure of the synthesized compounds is unambiguously proved by the method of NMR spectroscopy. The synthesized compounds are white crystalline substances soluble in hot alcohols, dioxane, DMF. The fact that 8-N,N-diethylamino-7-ethyl-3-methylxanthine and 7-ethyl-8-(midazol-1)-3-methylxanthine are well soluble in diluted acid solutions, can be used to obtain new bioactive salts with organic and inorganic acids. The presence of free N 1 H group enables the synthesis of new 1,3,7,8-tetrasubstituted of xanthine by the introduction of a variety of electrophilic reagents into the position of 1 uracil part of the molecule. Conclusions . Simply implemented methods for the synthesis of 8-amino-7-methylxanthine are developed. NMR-spectroscopic study of the obtained compounds, which clearly confirms their structure, is conducted. The prospective of the synthesized compounds for subsequent modification of their structure is demonstrated.

Intermediate derivatisation method in the discovery of new acaricide candidates: synthesis of N‐substituted piperazine derivatives and their activity against phytophagous mites

To discover and exploit novel acaricidal compounds, a series of novel N-substituted piperazine derivatives were designed and synthesised using a tert-butyl piperazine-1-carboxylate as the starting material by intermediate derivatisation methods, and their acaricidal activities were evaluated. Compounds 11 and 12 exhibited significant acaricidal activity against adults of Tetranychus cinnabarinus in greenhouse tests. Compound 12, in particular, was found to be the best potential candidate acaricide and proved to be more active than the commercial positive controls spirodiclofen and pyridaben, with an LC50 of 0.8977 mg L-1 . Results concerning acaricidal activity against larvae and eggs of T. cinnabarinus indicated that compound 12 possessed equivalent larvicidal activity to spirodiclofen and higher larvicidal activity than pyridaben. Meanwhile, compound 12 showed less ovicidal activity than pyridaben, but higher activity than spirodiclofen. Furthermore, the results of the field trial demonstrated that compound 12 could effectively control Panonychus citri and P. ulmi with long-lasting persistence and rapid action. The present work indicates that compound 12 could be a novel acaricide candidate for spider mite control. © 2016 Society of Chemical Industry.

Iridium-Catalyzed Asymmetric Ring-Opening of Oxabenzonorbornadienes with N-Substituted Piperazine Nucleophiles.

Iridium-catalyzed asymmetric ring-opening of oxabenzonorbornadienes with N-substituted piperazines was described. The reaction afforded the corresponding ring-opening products in high yields and moderate enantioselectivities in the presence of 2.5 mol % [Ir(COD)Cl]2 and 5.0 mol % (S)-p-Tol-BINAP. The effects of various chiral bidentate ligands, catalyst loading, solvent, and temperature on the yield and enantioselectivity were also investigated. A plausible mechanism was proposed to account for the formation of the corresponding trans-ring opened products based on the X-ray structure of product 2i.

GC-MS and IR studies on the six ring regioisomeric dimethoxyphenylpiperazines (DOMePPs).

A number of N-substituted piperazines have been described as drugs of abuse in recent years. This new drug category includes several series of aromatic ring substituted phenylpiperazines. The wide variety of available precursors makes regioisomerism a significant issue in these totally synthetic compounds. In this study, a complete series of regioisomeric dimethoxyphenylpiperazines were synthesized and evaluated using GC-MS and FT-IR. The EI mass spectra show fragments characteristic of both the dimethoxyphenyl and the piperazine portions of the molecules including the dimethoxyphenylaziridinium cation (m/z 180) and dimethoxyphenyl cation (m/z 137). The ion at m/z 56 for the C3H6N(+) fragment is characteristic of the piperazine ring and was observed in all the spectra. The perfluoroacyl derivatives were resolved by GC, and their mass spectra showed some differences in relative abundance of ions. FTIR provides direct confirmatory data for differentiation between the regioisomeric dimethoxyphenylpiperazines, and GC separation was accomplished on an Rtx-200 phase.