Arylpiperazine Moiety Research Articles

Alpha1-adrenoceptor antagonists. 6. Structural optimization of pyridazinone-arylpiperazines. Study of the influence on affinity and selectivity of cyclic substituents at the pyridazinone ring and alkoxy groups at the arylpiperazine moiety.

In continuing our search for selective alpha(1)-adrenoceptor (AR) antagonists, we have synthesized new alkoxyarylpiperazinylalkylpyridazinone derivatives. The new compounds were tested for their affinity toward alpha(1)- and alpha(2)-AR and toward the 5-HT(1A) receptor. alpha(1)-AR affinity data are in the subnanomolar range, with 3 showing an affinity of 0.052 nM, about 5-fold higher than prazosin. None of the studied compounds was found to be alpha(1)/alpha(2) selective, but 8 showed an interesting 5-HT(1A)/alpha(1) affinity ratio of 119.

α1‐Adrenoceptor Antagonists. Part 5. Pyridazinone‐arylpiperazines. Probing the Influence on Affinity and Selectivity of Both ortho‐Alkoxy Groups at the Arylpiperazine Moiety and Cyclic Substituents at the Pyridazinone Nucleus.

α₁‐Adrenoceptor Antagonists. Part 5. Pyridazinone‐arylpiperazines. Probing the Influence on Affinity and Selectivity of Both ortho‐Alkoxy Groups at the Arylpiperazine Moiety and Cyclic Substituents at the Pyridazinone Nucleus.

Synthesis of New Hexahydro‐ and Octahydropyrido[1,2‐c]pyrimidine Derivatives with an Arylpiperazine Moiety as Ligands for 5‐HT1A and 5‐HT2A Receptors.

AbstractFor Abstract see ChemInform Abstract in Full Text.

α 1-Adrenoceptor antagonists. 5. Pyridazinone-arylpiperazines. Probing the influence on affinity and selectivity of both ortho-Alkoxy groups at the arylpiperazine moiety and cyclic substituents at the pyridazinone nucleus

Our previous work on pyridazinone–arylpiperazine derivatives suggested some structural features that a compound should have to show high affinity and good selectivity for α 1 adrenoceptors (AR) with respect to α 2-AR. Accordingly, two classes of new alkoxyphenylpiperazinylheptylpyridazinones were designed and synthesized to evaluate the effect of the alkoxy substituent on affinity and selectivity. As expected, affinity increased with larger alkoxy groups. Affinity values are all comparable with that of the reference compound (prazosin), with the exception of compound 1c found 4.5-fold more active than prazosin.

Synthesis of new hexahydro- and octahydropyrido[1,2- c]pyrimidine derivatives with an arylpiperazine moiety as ligands for 5-HT 1A and 5-HT 2A receptors

Synthesis applied to prepare compounds 5– 15 and 17– 22 discussed in this paper has been presented in Scheme 1. Multi-stage preparation techniques were used to obtain 4-aryl-hexahydro 1– 4 and ( R, R) and ( S, S) 4-aryl-octahydropyrido[1,2- c]pyrimidine-1,3-dione ( 16) derivatives, being the starting compounds for further modification. N-Alkylation of the imide group in compounds 1– 4 and 16 followed, using 1,4-dibromobutane to yield monobromobutyl derivatives 5– 8 and 17. Subsequent condensation of those compounds with appropriate 1-aryl or 1-heteroarylpiperazine led to the final hexahydro- 9– 15 and octahydro- 18– 22 pyrido[1,2- c]pyrimidine-1,3-dione derivatives. The final products were subjected to screening test to elucidate the affinity to 5-HT 1A and 5-HT 2A receptors.

Synthesis, biological evaluation, and pharmacophore generation of new pyridazinone derivatives with affinity toward alpha(1)- and alpha(2)-adrenoceptors.

A series of new pyridazin-3(2H)-one derivatives (3 and 4) were evaluated for their in vitro affinity toward both alpha(1)- and alpha(2)-adrenoceptors by radioligand receptor binding assays. All target compounds showed good affinities for the alpha(1)-adrenoceptor, with K(i) values in the low nanomolar range. The polymethylene chain constituting the spacer between the furoylpiperazinyl pyridazinone and the arylpiperazine moiety was shown to influence the affinity and selectivity of these compounds. Particularly, a gradual increase in affinity was observed by lengthening the polymethylene chain up to a maximum of seven carbon atoms. In addition, compound 3k, characterized by a very interesting alpha(1)-AR affinity (1.9 nM), was also shown to be a highly selective alpha(1)-AR antagonist, the affinity ratio for alpha(2)- and alpha(1)-adrenoceptors being 274. To gain insight into the structural features required for alpha(1) antagonist activity, the pyridazinone derivatives were submitted to a pharmacophore generation procedure using the program Catalyst. The resulting pharmacophore model showed high correlation and predictive power. It also rationalized the relationships between structural properties and biological data of, and external to, the pyridazinone class.

Synthesis and in vitro and in vivo functional studies of ortho-substituted phenylpiperazine and N-substituted 4-N-(o-methoxyphenyl)aminopiperidine analogues of WAY100635.

WAY100635 (2), N-[2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl]-N-(2-pyridinyl)cyclohe xanecarboxamide, is a silent serotonin 5-HT(1A) antagonist, which is now widely used to study the 5-HT(1A) receptor both in vivo and in vitro. In this paper, we describe the synthesis and in vitro (5-HT(1A) affinity and pA(2) values at guinea pig ileum strips) and in vivo (hypothermia and ultrasonic vocalization) pharmacology at the serotonin 5-HT(1A) receptor of several closely related analogues of 2. Test compounds 12 and 14, in which the arylpiperazine moiety of 2 has been replaced by an arylaminopiperidine moiety, showed no affinity or antagonistic activity at the 5-HT(1A) receptor. Substitution of the o-methoxy group of 2 by larger fluoroalkoxy or sulfonyloxy substituents did not alter the in vitro or in vivo pharmacology to any great extent; in vivo both the fluoropropyl analogue 5 and the triflate analogue 7 are equipotent to WAY100635 itself. The O-desmethyl analogue 3 proved to be the most potent antagonist at the serotonin 5-HT(1A) postsynaptic receptor sites in this series.

Novel benzothiazolin-2-one and benzoxazin-3-one arylpiperazine derivatives with mixed 5HT1A/D2 affinity as potential atypical antipsychotics.

Since it was known that 5HT properties (5HT1A agonism or 5HT2A antagonism) combined with D2 antagonism may lead to atypical antipsychotic drugs, a series of 19 benzothiazolin-2-one and benzoxazin-3-one derivatives possessing the arylpiperazine moiety was prepared, and their binding profiles were investigated. All tested compounds displayed very high affinities for the 5HT1A and D2 receptors. Therefore, further pharmacological studies were carried out on selected compounds (24, 27, 30, 46, and 47). This evaluation in rats clearly revealed potent antipsychotic properties along with a decrease of extrapyramidal side effects. These derivatives are currently under preclinical development.

Alkoxyfurocoumarin derivatives as potential mesolimbic selective antipsychotics

Summary A series of potential antipsychotic compounds have been synthesized by combining a furocoumarin heterocycle through a linker of different sizes with an arylpiperazine or piperidine moiety. Several of the compounds show very high affinity for the dopamine-D 1 and -D 2 , α 1 -adrenergic and serotonin 5-HT 2 receptors in vitro and selected compounds, eg, 3k, 3n and 3p , were active in in vivo models predictive of antipsychotic activity. In mice the compounds potently antagonized methylphenidate-induced motility while methylphenidate-induced gnawing was unaffected. In rats the compounds inhibited condition avoidance responding without causing catalepsy.

N4-unsubstituted N1-arylpiperazines as high-affinity 5-HT1A receptor ligands.

In order to explore the structural requirements for high 5-HT1A affinity, a series of aryl-substituted N1-phenylpiperazines were synthesized and evaluated for their ability to displace [3H]-8-OH-DPAT from its specific binding sites in rat frontal cortex homogenates. We found 2-methoxy substitution to be favorable, while 4-methoxy substitution was detrimental for 5-HT1A affinity. Substitution with annelated rings at the 2,3-positions was highly favorable for all investigated compounds, with the exception of a pyrrole ring. All other substitutions, except fluoro, in this class of heterobicyclic phenylpiperazines decreased affinity in the order: ortho > para > meta. The loss of affinity in the ortho and para positions is probably due to steric factors: the substituents either cause steric hindrance with the receptor or prevent the compound from adopting the appropriate conformation for binding to the 5-HT1A receptor. Conformational analysis combined with structure-affinity relationships (SAR) indicates that our arylpiperazines may bind at the 5-HT1A receptor in a nearly coplanar conformation. Observed interactions of the compounds in our 5-HT1A receptor model appeared to be in agreement with SAR data. The aromatic part of the arylpiperazine moiety has pi-pi interactions with the aromatic residues Trp161 and Phe362 in helices IV and VI, respectively. The positively charged protonated basic nitrogen forms a hydrogen bond with the negatively charged Asp116 in helix III. The ammonium-aspartate complex is surrounded by aromatic residues Trp358 and Phe361 in helix VI. A lipophilic pocket is formed by Phe362, Leu366 (both helix VI), and the methyl group of Thr200 (helix V). In agreement with the model, addition of a methyl substituent to the structure of the benzodioxine analogue 12 in this region, yielding 13, is favorable for 5-HT1A receptor affinity. Unfavorable positions for substitution with bulky groups, like the 3- and 4-positions in the benzofuran compound 14, are explained by steric hindrance with the backbone atoms of helix V. Thus, we were able to rationalize the 5-HT1A SAR of existing N1-phenylpiperazines, as well as a series of newly synthesized bicyclic heteroarylpiperazines, in terms of receptor-ligand interactions. Several of these N4-unsubstituted compounds had affinities in the low-nanomolar range.

Electron impact mass spectra of new 5-substituted-2-amino-2-oxazolines

The electron impact mass spectra of fifteen 5-substituted-2-amino-2-oxazolines classified in two series according to the nature of the substituent are discussed. For the 5-(l-aryl-4-piperazino)methyl compounds the main fragments are derived from the arylpiperazine moiety, whereas for the phenoxymethyl compounds the main ions are derived from the heterocyclic oxazoline ring.

Antivertigo agents. V. Quantitative structure-activity relationships of 6-[2-(4-aryl-1-piperazinyl)ethyl]-5,6,7,8-tetrahydro-1,6-naphthyridine s.

The quantitative structure-activity relationships (QSAR) between the molecular structures and antivertigo activities of 6-[2-(4-aryl-1-piperazinyl) ethyl]-5, 6, 7, 8-tetrahydro-1, 6-naphthyridines were investigated. The effects of the ortho-, meta-, and para-substituents on the phenyl ring of the arylpiperazine moiety were examined by means of regression analysis using various physicochemical parameters related to these substituents. The results showed that only the parameters concerning the ortho-substituent were statistically significant. Namely, the relative activity depended on both Fortho (Swain-Lupton field effect constant of the ortho-substituent) and I (indicator variable for the presence of an ortho-alkoxy group and an ortho-dimethylamino group). Thus, regression analysis for only the ortho-substituted compounds was examined and afforded a result similar to that described above. Further, the net atomic charge calculated by the molecular orbital method besides free energy-related substituent parameters was used as electronic parameters of the ortho-substituents on the phenyl ring for this QSAR analysis. For the ortho-substituted compounds alone, the potency correlated well with the net atomic charge on the first atom of the ortho-substituent (Qortho), while the correlation for all the compounds (ortho-, meta-, and parasubstituents) was slightly lower than that for the ortho-substituted compounds alone. It was found that increase in the negative net atomic charge on the first atom of the ortho-position increased the relative activity. The correlation between Qortho and Fortho and I was examined and the role of I is discussed in connection with hydrogen bond-forming ability. The interaction between the arylpiperazine moiety in the compound and a putative receptor is discussed based on the QSAR analysis.

Identification and quantitation of 1-arylpiperazines, metabolites resulting from side-chain cleavage of (4-substituted aryl-1-piperazinyl)alkyl heterocyclic derivatives in rat plasma and brain

Many drugs contain the arylpiperazine moiety in the side-chain of their molecules. A common metabolic pathway of such drugs is cleavage of the side-chain with the formation of 1-arylpiperazines. This has been verified by combined gas chromatography-mass spectrometry of biological samples from rats given orally a series of heterocyclic derivatives bearing a 4-aryl(phenyl, pyrimidinyl, pyridyl or thiazolyl)-1-piperazinylalkyl moiety (oxypertine, zolertine, millipertine, empiprazole, dapiprazole, antrafenine, piribedil, azaperone). A sensitive and selective electron-capture gas-liquid chromatographic procedure for 1-arylpiperazines in rat plasma and brain is described. The overall recovery from plasma and brain was 70–90%. The limit of detection for substituted (halogenated) phenylpiperazines was 10–25 ng/ml or ng/g and 25–100 ng/ml or ng/g for other derivatives. Preliminary data are reported on the time course of the production and elimination of 1-arylpiperazines after oral administration of representative compounds with the arylpiperazine moiety (oxypertine, azaperone and S-3608).