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PubMed2004

N,N-Dialkylated 4-(4-arylsulfonylpiperazine-1-carbonyl)-benzamidines and 4-((4-arylsulfonyl)-2-oxo-piperazin-1-ylmethyl)-benzamidines as potent factor Xa inhibitors.

A class of N,N-dialkylated 4-(4-arylsulfonylpiperazine-1-carbonyl)-benzamidines and 4-((4-arylsulfonyl)-2-oxo-piperazin-1-ylmethyl)-benzamidines has been discovered as potent factor Xa inhibitors with desirable in vitro and in vivo anticoagulant activity, but with low oral bioavailability. The 5-chloroindole and 6-chlorobenzo[b]thiophene groups are optimal as the factor Xa S1 binding elements. The strategy of incorporating a side chain on the piperazine nucleus to enhance binding affinity has been examined.

Benzamidines↗

PubMedDate not supplied

The solid-phase synthesis and use of N-monosubstituted piperazines in chemical library synthesis.

An efficient solid-phase synthesis of mono-N-substituted piperazines is presented. The key transformation involves a selective borane amide bond reduction in the presence of a carbamate resin linkage. This synthetic route takes advantage of the large diverse pool of commercially available carboxylic acids, acid chlorides, and sulfonyl chlorides. The solid-phase approach facilitates parallel processing by eliminating the need for column chromatography after each synthetic step. The N-monosubstituted piperazines were shown to react with polymeric activated tetrafluorophenol (TFP) reagents to generate arrays of amides and sulfonamides in good purity for biological testing.

Journal Article↗

PubMed1993

Synthesis and evaluation of conformationally restricted N-[2-(3,4-dichlorophenyl)ethyl]-N-methyl-2-(1-pyrrolidinyl)ethylamines at sigma receptors. 2. Piperazines, bicyclic amines, bridged bicyclic amines, and miscellaneous compounds.

As a continuation of our earlier study (J. Med. Chem. 1992, 35, 4334-4343) we conformationally restricted the sigma-receptor ligand 2-(1-pyrrolidinyl)-N-[2-(3,4-dichlorophenyl)ethyl]-N-methylethylamine (1) by incorporating it into a series of homologous piperazines 3-9 and homopiperazines 10 and 11, diazabicyclononanes and decanes, bridgehead bicyclooctanes and nonanes as well as other miscellaneous compounds. sigma-Receptor binding affinities were obtained using [3H](+)-pentazocine in guinea pig brain membrane sigma 1 sites. The studies suggest that the nitrogen lone pair orientation found in the piperazines affords the strongest binding interaction. Other nitrogen lone pair orientations or compounds representing unlikely staggered conformations of 1 [ as in 4-[2-(3,4-dichlorophenyl)ethyl]-1,4-diazabicyclo[3.2.2]nonane (16)] show very weak sigma interaction. Comparison of the binding data of different N-substituted homologues of 1 with those of the 1-[2-(3,4-dichlorophenyl)ethyl]-4-alkylpiperazines suggests that the two nitrogen atoms of 1 are working in opposition to one another in terms of their sensitivity to steric bulk. The high binding affinity of the 1,4-diazabicyclo[4.3.0]nonanes 12 suggests that these may approximate the methyl and pyrrolidine ring conformations found in 1 when it is bound to the sigma receptor. Compound 12 exhibited a 4-fold enantioselectivity favoring (+)-12. The synthesis of 6,7-dichloro-2-[[2-(1-pyrrolidinyl)ethyl]amino]tetralin (19) and its desmethyl derivative 20 permitted constraint of the 3,4-dichlorophenyl and N-methyl moieties of 1 into a gauche orientation. The binding data suggests that this conformation in 1 favors strong binding interaction at sigma-receptors. sigma-Receptor Ki's ranged from 0.55 nM for 1-[2-(3,4-dichlorophenyl)ethyl]-4-n-butylpiperazine (7) to 654 nM for 16. Overall comparison of the results indicate that 1 is subject to considerable conformational freedom and suggests that the sigma receptor is not subject to rigid stereochemical restraints with 1. These results add to our earlier study where we restrained 1 using simple monocyclic heterocycles.

Animals↗

PubMed1989

Structure-activity relationships in prazosin-related compounds. Effect of replacing a piperazine ring with an alkanediamine moiety on alpha 1-adrenoreceptor blocking activity.

Several prazosin-related compounds were synthesized in which the piperazine ring of prazosin (1) was replaced by an alkanediamine chain and were evaluated for their blocking activity on alpha 1- and alpha 2-adrenoreceptors in isolated rat vas deferens. All the compounds investigated proved highly selective toward the alpha 1-adrenoreceptor owing to a very low affinity for alpha 2-adrenoreceptors. Furthermore, compounds 2, 9, and 13 were also investigated in vivo to determine their hypotensive effect on anesthetized rats, which were compared with that of prazosin (1). It was confirmed that the piperazine moiety of 1 is not essential for potency. However, optimum activity depends on two parameters: carbon-chain length of the alkanediamine moiety and N-methylation of both the amide and the 2-amino functions. In the desmethyl series, optimum activity was associated with the lower homologues (2-4) bearing a chain of two to four methylenes whereas in the N,N'-dimethyl series peak potency was observed with a six-carbon chain as in 13. Compound 13 proved the most active of the series and was more potent than prazosin (1) in both in vivo and in vitro assays. It is hypothesized that the alpha 1-adrenoreceptor incorporates a lipophilic area that is located between the binding sites for the quinazoline and the furoyl moieties and is able to accommodate a polymethylene chain.

Adrenergic alpha-Antagonists↗

PubMed2003

Synthesis of 2,6-bridged piperazine-3-ones by N-acyliminium ion chemistry.

Several 2-substituted and 2,5-disubstituted piperazine-3,6-diones were synthesized starting from readily available alpha-amino acids. After activation of a lactam carbonyl via introduction of a methoxycarbonyl group onto nitrogen, this carbonyl was selectively reduced. Treatment of the resulting urethane with protic acid generated the corresponding N-acyliminium ion, which was trapped by a nucleophilic C2-side chain to provide 2,6-bridged piperazine-3-ones. Several aromatic, heteroaromatic, and nonaromatic side chains were used as pi-nucleophiles. In addition, the effect of the presence of a C5-methyl group on the stereochemical outcome of the cyclization was examined.

Journal Article↗

PubMed2004

Complexation of metals with piperazine-containing azamacrocyclic fluorophores.

Azamacrocyclic fluorophores containing piperazine units were synthesized using sequential rhodium-catalyzed regioselective hydroformylation-reductive amination. A piperazine unit is introduced into the macrocycles to act simultaneously as electron donor and binding site. The macrocycles chelate divalent cations, either Zn2+ or Co2+, which considerably enhanced fluorescence. Complexation with Zn2+ was additionally confirmed by NMR.

Journal Article↗

PubMed2004

Use of physicochemical calculation of pKa and CLogP to predict phospholipidosis-inducing potential: a case study with structurally related piperazines.

Several cationic amphiphilic compounds are known to induce phospholipidosis, a condition primarily characterized by excessive accumulation of phospholipids in different cell types, giving the affected cells a finely foamy appearance. Excessive storage of lamellar membranous intralysosomal inclusion bodies is the hallmark for phospholipidosis on the electron microscopic level. In case of alveolar phospholipidosis, foamy macrophages accumulate within the alveolar spaces of the lung. Based on such findings in a one-year toxicity study with gepirone in rats, we studied the molecular properties of this compound and compounds suspected of being phospholipidosis inducers by means of physicochemical calculations. Physicochemical molecular calculations of molecular weight, ClogP (partition coefficient octanol/water), logD at pH 7.4, and pKa were performed, for the cationic amphiphilic compounds chlorpromazine, amiodarone, imipramine, propranolol and fluoxetine, and for the structurally related compounds 1-phenylpiperazine (1-PHP), gepirone (and its major metabolites, 3-OH-gepirone and 1-pyrimidinylpiperazine [1-PP]), and buspirone. ClogP and calculated pKa cluster differently for the amphiphilic drugs compared to the chemical series of piperazines. In line with this analysis, lamellar inclusion bodies were found in an in vitro validation experiment in the human monoblastoid cell line U-937, incubated for 96 h at 10 microg/mL with cationic amphiphilic drugs (amiodarone, imipramine, or propranolol). No such lamellar inclusion bodies were seen for any of the compounds from the chemical series of piperazines including gepirone and its metabolites. The data presented support the use of simple physicochemical calculations of ClogP and pKa to discriminate rapidly between compounds suspected of being phospholipidosis inducers. Finally, the discriminative power of these physicochemical ClogP and pKa calculations to predict phospholipidosis-inducing potential was further validated by extension of the set of compounds.

Administration, Oral↗

PubMed2002

Piperazine-1,4-diium--2,4-dinitrophenolate--water (1/2/2).

In the title 1/2/2 adduct, C(4)H(12)N(2)(2+) x 2C(6)H(3)N(2)O(5)(-) x 2H(2)O, the dication lies on a crystallographic inversion centre and the asymmetric unit also has one anion and one water molecule in general positions. The 2,4-dinitrophenolate anions and the water molecules are linked by two O-H...O and two C-H...O hydrogen bonds to form molecular ribbons, which extend along the b direction. The piperazine dication acts as a donor for bifurcated N-H...O hydrogen bonds with the phenolate O atom and with the O atom of the o-nitro group. Six symmetry-related molecular ribbons are linked to a piperazine dication by N---H.O and C---H.O hydrogen bonds.

Journal Article↗

PubMed2004

Structures of piperazine, piperidine and morpholine.

The crystal structures of piperazine, piperidine and morpholine have been determined at 150 K. All three structures are characterized by the formation of NH...N hydrogen-bonded chains. In piperazine these are linked to form sheets, but the chains are shifted so that the molecules interleave. In morpholine there are in addition weak CH...O interactions. Topological analyses show that these three structures are closely related to that of cyclohexane-II, which can be described in terms of a pseudo-cubic close-packed array of molecules in a familiar ABC layered arrangement. While the positions of the molecules within each layer are similar, hydrogen bonding occurs between the ABC layers and in order to accommodate this the molecules are rotated relative to those in cyclohexane-II. Piperidine and morpholine also adopt layered structures, with hydrogen-bonding or CH...O interactions between the layers. In these cases, however, the layering more resembles a hexagonal close-packed arrangement.

Journal Article↗

PubMed2000

Piperazine oestrone sulphate and interrupted norethisterone in postmenopausal women: effects on bone mass, lipoprotein metabolism, climacteric symptoms, and adverse effects.

OBJECTIVE: To compare the effects of two doses of piperazine oestrone sulphate combined with interrupted norethisterone, with that of oestradiol continuously combined with norethisterone acetate, and with placebo, in postmenopausal women. DESIGN: A prospective randomised trial. PARTICIPANTS: Two hundred postmenopausal women. SETTING: Monocentre study with expertise in osteoporosis. METHODS: The participants were randomly assigned to two years of treatment with alternating three-day cycles of 1.5 mg of piperazine oestrone sulphate plus 0.7 mg of norethisterone (highEP), or alternating three-day cycles of 0.75 mg of piperaine oestrone sulphate plus 0.35 mg of norethisterone (lowEP), or 2 mg of 17beta-oestradiol continuously combined with 1 mg of norethisterone acetate (E2+NETA), or placebo. MAIN OUTCOME MEASURES: Change in bone mineral density, lipoprotein metabolism, climacteric symptoms, and adverse effects. RESULTS: One hundred and twenty-one women completed the study. Spinal bone mineral density was increased about 9% over two years by E2+NETA, about 6% by highEP, 4% by lowEP, but remained unchanged in the placebo group. The same pattern was seen in the hip and forearm. All hormone regimens decreased markers of bone turnover and alleviated climacteric symptoms. Serum lipoproteins decreased by about 10% in all hormone groups. CONCLUSIONS: All hormone regimens studied prevented bone loss completely and lowered serum lipids.

Aged↗

PubMed1986

Local cerebral glucose utilisation following indoleamine- and piperazine-containing 5-hydroxytryptamine agonists.

Substances with varying structural components have been shown to have 5-hydroxytryptamine (5-HT)-like properties in the CNS. In this study, putative 5-HT agonists with indoleamine moeities--lysergic acid diethylamide (LSD) and 5-methoxy-N,N-dimethyltryptamine (5-MeODMT)--and with piperazine moieties--quipazine (Quip) and 6-chloro-2-(1-piperazinyl)pyrazine (6-CPP) were administered to rats. Local cerebral glucose utilisation was measured using the [14C]2-deoxyglucose autoradiographic technique. It was found that in most cerebral structures, these substances produced dose-dependent reductions in glucose utilisation. However, Quip and 6-CPP increased glucose utilisation in specific areas of the diencephalon (e.g., nucleus reuniens) and produced a biphasic effect in some but not all extrapyramidal structures (e.g., ventromedial caudate nucleus). No such increases in local cerebral glucose utilisation were measured following LSD or 5-MeODMT administration. These results indicate that although similarities exist between the effects of indoleamine- and piperazine-containing 5-HT agonists on local cerebral glucose utilisation there are also significant differences in the overall patterns of response produced.

Animals↗

PubMed1995

Continuous combined piperazine oestrone sulphate and medroxyprogesterone acetate hormone replacement therapy--a study of bleeding pattern, endometrial response, serum lipid and bone density changes.

This pilot study was conducted to establish the optimum oral dosage of medroxyprogesterone acetate (Provera) given daily in combination with a fixed dose of piperazine oestrone sulphate (Ogen), as hormone replacement therapy. A group of 32 nonhysterectomized, symptomatic menopausal women were randomly allocated to receive piperazine oestrone sulphate 1.25 mg daily and medroxyprogesterone acetate 2.5 mg, 5 mg or 10 mg daily for a 2-year period. This was an open study and the patients were reviewed at 3-monthly intervals for 2 years. Vaginal bleeding was reported by 58% of patients after the first 3 months of treatment. There was a gradual decline in the reported incidence of bleeding over the following 6 months particularly by women in the 5 mg and 10 mg Provera group. Only 10% of patients were still recording slight bleeding in the 10 mg group at 12 months. By 24 months all the women in the 5 mg and 10 mg Provera groups had ceased bleeding. There were 2 patients in the 2.5 mg Provera group with persistent proliferative endometrium at 24 months. All the remaining patients had atrophic endometrium. There was no significant difference in serum lipid changes between the 3 groups, but there was an overall reduction in total cholesterol, triglycerides and low density lipoprotein cholesterol in all women. There was no significant difference in bone mineral density changes between the groups over the 2-year period. Endometrial protection with increased incidence of amenorrhoea, without significant adverse effects, was seen with the use of 5 mg and 10 mg of provera.

Administration, Oral↗

PubMed1994

Placement of alkyl substituents on the C-7 piperazine ring of fluoroquinolones: dramatic differential effects on mammalian topoisomerase II and DNA gyrase.

Several substituted analogs of 7-(cis-3,5-dimethylpiperazinyl)-6,8-difluoro-5-amino-1-cyclopropyl quinolone were prepared and tested in a DNA cleavage assay with calf thymus topoisomerase II. Positioning of the methyl groups on the C-7 piperazine ring influenced potency against the mammalian enzyme; the cis-3,5-dimethyl configuration did not stimulate cleavage at drug concentrations less than or equal to 2,000 microM, while the trans configuration was active at drug levels as low as 36 microM. Removal of the cis-methyl groups produced a compound that was only sixfold less potent than the antitumor agent etoposide in stimulating enzyme-mediated DNA cleavage. The cis- and trans-methyl substitutions on the piperazine that conferred potency against the mammalian type II enzyme had little effect on bacterial DNA gyrase cleavage activity, suggesting that an asymmetric barrier exists with the mammalian enzyme which influences productive quinolone interaction, favoring the less bulky trans-3,5-dimethylpiperazine substituent at C-7.

Animals↗

PubMed2003

Crystal structure of [1,4-bis[1-(3,5-dichlorophenolato-2-ylmethyl)-ylpropylamino-kappa2N,O]piperazine-kappa2N,N']cobalt(II).

The X-ray crystal structure of the title complex, Co(Cl2bprpi) is described. In this complex the Co(II) center displays a distorted octahedral coordination geometry. The piperazine ring exhibits boat conformation, forming chelate rings and capping the Co atom. The N2-Col-N3 angle is 69.41(15) degrees, extremely smaller than 90 degrees. Because the small angle causes a large steric hindrance, the piperazine ring can be effective as an ion size-recognition site. The molecular structure is stabilized by intramolecular N-H...O hydrogen bonds and Cl...H contacts.

Journal Article↗

PubMed1974

Pyrantel embonate in mass treatment of ascariasis and comparison with piperazine adipate and santonin-kainic acid complex.

A single dose (2.0, 5.0, 10.0 mg/kg) of pyrantel embonate given to three groups consisting 301 children with Ascaris lumbricoides infection achieved a cure rate of 91.3%, 94.4% and 98.9% respectively. Whereas in the other two groups of 71 and 75 patients who received 75 mg/kg body weight with piperazine adipate 2 or 3 consecutive days, the cure rates were 62.0% and 74.7% respectively. Administration of a single recommended dose of santonin-kainic acid complex given to 77 patients achived a cure rate of 80.5% with 91.0% of egg reduction rate. The cure rate resulting from a single lowest dose 2.5 mg/kg pyrantel embonate was significantly higher than those of piperazine adipate and santonin-kainic acid complex in the mass treatment for ascariasis. in addition to the group of 2.5 mg/kg pyrantel embonate treatment, the side effect was lesser than those of the other groups. Considering the efficacy and safety of pyrantel embonate against Ascaris lumbricoides, it would be one of the useful agents for the mass treatment of Ascaris control.

Journal Article↗

PubMed2002

New 3-[4-(3-substituted phenyl)piperazin-1-yl]-1-(benzo[b]thiophen-3-yl)propanol derivatives with dual action at 5-HT1A serotonin receptors and serotonin transporter as a new class of antidepressants.

In this paper a series of new 3-[4-(3-substituted phenyl)piperazin-1-yl]-1-(benzo[b]thiophen-3-yl)propanol derivatives is presented as a new class of antidepressant drugs with dual activity at 5-HT1A serotonin receptors and serotonin transporter. The 5-HT1A receptor and 5-HT transporter binding affinities of hydroxylic compounds 4 a-e have been determined. The new compounds present nanomolar affinity for both activities, and 1-(benzo[b]thiophen-3-yl)-3-[4-(3-methoxyphenyl)piperazin-1-yl]propan-1-ol (4d) shows values (nM) of Ki = 86 for 5-HT1A receptors and Ki = 76 for the serotonin transporter, respectively.

Antidepressive Agents, Second-Generation↗

PubMedDate not supplied

[The pharmacology of 1-(2-pyrimidinyl)piperazine, a metabolite of buspirone].

In experiments on rats the anxiolytic activity of 1-(2-pyrimidinyl)-piperazine (PP) was revealed only in some models of anxiety states, although diazepam was effective in all used models. In contrast to diazepam, PP exerts the anesthetic-potentiating and myorelaxant effects only when administered in subtoxic doses and possesses no anticorazole activity. The facts testifying to the serotoninergic mechanisms of the anxiolytic action of 1-(2-pyrimidinyl)-piperazine are presented.

Animals↗

PubMed1993

Synthesis and potential anthelmintic activity of methyl-5-(4-salicyloyl-piperazin-1-yl)-benzimidazole-2-carbamates.

A series of methyl-5-(4-salicyloyl-piperazin-1-yl)-benzimidazole-2-carba mates (IX) has been prepared. 5-(4-Salicyloyl-piperazin-1-yl)-2-nitro anilines (VII) have been synthesized starting from 5-piperazino-2-nitro anilines and salicyloyl chlorides. Catalytic reduction of VII with Pd/C, followed by treatment with 1,3-dicarbomethoxy-S-methyl isothiourea, yielded the corresponding carbamates (IX), the anthelmintic activity of which was studied. Compound IXa significantly reduced the numbers of preadults, adults and encysted T. spiralis larvae in experimental mice.

Animals↗