alpha1-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

Synthesis and evaluation of novel thiazole moiety-containing compounds as antibreast cancer agents

Progesterone receptor (PR) agonists represent pivotal agents in trapping breast cancer cells through modulating the expression of estrogen receptor (ER). The present investigation aimed to test three novel thiadiazole-containing compounds as antibreast cancer agents. Test compounds were synthesized and abbreviated as 2-{(5-amino-1, 3, 4-thiazole-2-yl) amino}-4-(4-chloro-3-methylphenyl)-4-oxobutanoic acid (TAB), 4-(4-chloro-3-methylphenyl)-4-oxo 2-[(5-sulfanyl-1, 3, 4-thiadiazol-2-yl)] sulfanyl-butanoic acid (TSB) and 4-(4-chloro-3-methylphenyl)-4-oxo 2-[(5-sulfanyl-1, 3, 4-thiadiazol-2-yl)] sulphonyl-botanic acid (TSSB). Molecular docking of the test compounds with PR was simulated. The IC 50 of the test compounds against both Michigan cancer foundation-7 (MCF-7) and HepG2 was determined. Ehrlich solid tumor (EST) was grown in the right thigh of the mouse as a model of breast cancer in vivo . Hepatic and renal functions, besides hematological indicators, were tested. The expression of ER and ER genes in EST was determined using real-time PCR. Immunohistochemistry was carried out for the determination of Ki-67 and cyclin-dependent kinase 1 (CDK-1) in EST. Our results revealed that TAB, TSB and TSSB reduced Ehrlich tumor size by 48, 64 and 52%, respectively, compared to the EST control group. The docking scores achieved by TAB, TSB and TSSB with PR were -9.29, -9.41 and -9.24 kcal/mol, respectively. The most potent compound against MCF-7 was TSB, with an IC 50 of 3.9 g/ml. The administration of test compounds suppressed Ki-67 and CDK1, and the best effect was observed at TSB. Our findings suggest that test compounds are applicants to be antibreast cancer agents.

Efficient 1,3,4-Thiadiazole-4,5-dihydropyridazin-3(2H)-ones as Antimicrobial Agents

A set of novel series of 1,3,4-thiadiazolyl-sulfanyl-4,5-dihydropyridazin-3(2H)-ones with anticipated antimicrobial activity has been synthesized. The synthetic protocol of the targeted compounds was accomplished by treating β-aroylacrylic acid 1 with 5-amino-1,3,4-thiadiazole-2-thiol (2) to afford the thia-Michael adduct 3. Afterwards, the obtained thia-Michael adduct 3 was cyclized to 4,5-dihydropyridazin-3(2H)-ones 4a-d and the non-cyclized product hydrazone 5 by using different hydrazines. Moreover, adduct 3 was reacted with esters like diethyl malonate and ethyl acetoacetate affording 1,3,4-thiadiazolobutanamides 6a, b. Furthermore, the concurrent reaction of later butamides 6a, b with the hydrazine derivatives furnished thiadiazolopyridazin-3(2H)-ones 7a-d, 8, and butanoic acid 9.

X-ray Crystallography, DFT Calculations and Molecular Docking of Indole-Arylpiperazine Derivatives as α1A-Adrenoceptor Antagonists

Indole-arylpiperazine derivatives have exhibited good selectivity for the α_1A-adrenoceptor, but the structure-activity-binding mechanism relationship remains unclear. In the current study, three compounds (1, 2 and 3) were investigated through single-crystal X-ray diffraction analysis, density functional theory (DFT) calculations and molecular docking using a homology model of the α_1A receptor. Compounds 1 and 3 form H-bonds networks to stabilize their three-dimensional structures, while C–H···π interactions play a significant role in the packing of 2. Based on DFT-optimized conformations, the HOMO-LUMO energy gaps and molecular electrostatic potential (MEP) were theoretically calculated at the B3LYP/6-311G (d, p) level of theory. Chemical reactivity increases in the order of 3 < 2 < 1, and the maximum positive region of the MEP maps is mainly localized over the NH group. The binding mechanisms of ligand-α_1A-adrenoceptor complexes were illustrated by molecular docking. Binding to Gln177 of the second extracellular loop region via hydrogen bonds is likely to be essential for α_1A-selective antagonists. The present work sheds light on the studies of structure-activity-binding mechanism and aids in the design of α_1A antagonists with high selectivity.

Ultrasound-promoted regio and chemoselective synthesis of pyridazinones and phthalazinones catalyzed by ionic liquid [bmim]Br/AlCl3

The first ultrasound-promoted multicomponent synthesis of pyridazinones and phthalazinones from arenes, cyclic anhydrides and ArNHNH(2) in the presence of an efficient recyclable catalyst, [bmim]Br/AlCl(3), in high yield and short reaction time is reported.

Rational design, synthesis, biological evaluation, homology and docking studies of coumarin derivatives as α1 -adrenoceptor antagonists

According to a three-point pharmacophore for some uro-selective α(1) -adrenoceptor (AR) antagonists, a novel class of coumarin (=2H-1-benzopyran-2-one) derivatives have been successfully designed and synthesized with high efficacies for α(1) -AR. These synthesized coumarin derivatives exhibited high efficacies towards α(1) -AR in in vitro pharmacological assays. Compared with prazosin (pK(i) value of 8.77), among those coumarins, tolylpiperazine-substituted derivatives, 7 and 8, have comparable pK(i) values of 8.81 and 8.77, respectively. The trend in efficacies of these coumarin derivatives towards α(1A) -adrenoceptor was further rationalized by intensive molecular docking. Our work demonstrated that the designed coumarin derivatives can inhibit α(1) -AR in vitro. These findings will provide a guide for further studies of the medical therapy of benign prostatic hyperplasia (BPH).

A facile synthesis of pyridazinone derivatives under ultrasonic irradiation

A new, efficient and general method for preparation of N-substituted-pyridazinones using ultrasound irradiation is reported. Under ultrasound the reaction time decreases substantially, the yields are high and the reaction conditions are mild. It was noticed that substituents at the 3-(6)-position of pyridazone heterocycle have a substantial influence on the reactivity, while the effect of the substituents at the 1-(2)-position seems to be of minor importance. A comparative study of the reactions performed under ultrasound conditions versus at room temperature has been done.

Synthesis and biological affinity of new imidazo- and indol-arylpiperazine derivatives: further validation of a pharmacophore model for alpha(1)-adrenoceptor antagonists

In the continuing search for selective alpha(1)-adrenoceptor (AR) antagonists, new alkoxyarylpiperazinylalkylpyridazinone derivatives were designed and synthesized. The new compounds were tested for their affinity toward alpha(1)-AR, alpha(2)-AR and 5-HT(1A) receptors. The ability of these compounds to inhibit the serotonin transporters (SERT) was also determined. The pharmacological data confirm that increasing the size of the ortho alkoxy substituent on the phenyl ring of the arylpiperazine moiety afforded compounds with enhanced affinity toward the alpha(1)-AR. The isopropoxy group, the largest group evaluated, led the best alpha(1)-AR affinity profile. In contrast, the compounds which have an amide group within of the o-alkoxy-phenylpiperazine fragment showed low affinity toward the receptors studied. Similar results were obtained when the amide group was present in the linker of the junction between the two major constituents of the molecule.

Synthesis, alpha 1-adrenoceptor antagonist activity, and SAR study of novel arylpiperazine derivatives of phenytoin

In the search for new antiarrhythmic agents, some active 2-methoxyphenylpiperazine derivatives of phenytoin were obtained as a chemical modification of compound AZ-99 (3-ethyl-1-[2-hydroxy-3-(4-phenylpiperazin-1-yl)-propyl]-2,4-dioxo-5,5-diphenylimidazolidine). These compounds possessed structural properties similar to those of alpha(1)-adrenoceptor antagonists. In the present study, the affinities of the 2-methoxyphenylpiperazine derivatives (1a-3a) for alpha(1)- and alpha(2)-adrenoceptors were evaluated using radioligand ([(3)H]prazosin, [(3)H]clonidine) binding assays. In the next step, a new series of phenylpiperazine derivatives of phenytoin (4a-16a) containing 2-methoxyphenyl-, 2-ethoxyphenyl-, 2-pyridyl- or 2-furoylpiperazine moiety, as well as, various ester or alkyl substituents at 3-position of hydantoin ring were synthesized. The newly synthesized compounds were tested for their affinity to alpha(1)- and alpha(2)-adrenoceptors. They have shown affinities for alpha(1)-adrenoceptors at nanomolar to submicromolar range. Some compounds were moderately selective ligands of alpha(1)-adrenoceptors. Selected compounds (3a-5a, 7a, 13a, 14a) were also evaluated for their alpha(1)-adrenoceptor antagonistic properties in functional bioassays. A SAR study indicated that the most active compounds contain 2-alkoxyphenylpiperazine moieties and methyl or 2-methylpropionate substituent at 3-N position in hydantoin. The exchange of 2-alkoxyphenyl moiety into 2-furoyl or 2-pyridyl group significantly decreased affinities for alpha(1)-adrenoceptors. Molecular modelling results obtained using conformational analysis CONFLEX and PM5 method for geometry optimization, allowed for comparison of the spatial properties of tested compounds with pharmacophore model created by Barbaro et al. for the ideal alpha(1)-adrenoceptor antagonist.

Synthesis of new piperazine–pyridazinone derivatives and their binding affinity toward α1-, α2-adrenergic and 5-HT1A serotoninergic receptors

We report the design and synthesis of a new class of piperazine-pyridazinone analogues. The arylpiperazine moiety, the length of the spacer, and the terminal molecular fragment were varied to evaluate their influence in determining the affinity of the new compounds toward the alpha1-adrenergic receptor (alpha1-AR), alpha2-adrenergic receptor (alpha2-AR), and the 5-HT1A serotoninergic receptor (5-HT1AR). Biological data showed that most of the compounds have an alpha1-AR affinity in the nanomolar or subnanomolar range, while affinity toward the other two receptors was lower in most cases. However, several of the tested compounds also showed very good (in the nanomolar range) or moderate affinity toward the 5-HT1AR subtype.

Synthesis and development of new 2-substituted 1-[3-(4-arylpiperazin-1-yl)propyl]-pyrrolidin-2-one derivatives with antiarrhythmic, hypotensive, and α-adrenolytic activity

A series of new 1-[3-(4-arylpiperazinyl-1-yl)-2-(N-alkylcarbamoyloxy)propyl]-pyrrolidin-2-one derivatives (4a-12a) were synthesised and tested for their electrocardiographic, antiarrhythmic and antihypertensive activity, as well as for the alpha1- and alpha2-adrenoceptor binding affinities. Of the newly synthesised derivatives, 1-{2-(N-2-methylethylcarbamoiloxy)-3-[4-(2-methoxyphenyl)piperazin-1-yl)]propyl}pyrrolidin-2-one dihydrochloride (10a) was the most active in prophylactic antiarrhythmic tests, its ED50 value equalling 2.7 mg kg(-1), and the therapeutic index being 75.2; moreover, compound 10a was also found to possess hypotensive activity. A preliminary molecular modelling study suggested that the selected alpha1-AR antagonist distances and angles between pharmacophoric features, estimated for the tested compounds, were in good agreement with the parameters evaluated for ligands.

Synthesis of 3-Arylpiperazinylalkylpyrrolo[3,2-d]pyrimidine-2,4-dione Derivatives as Novel, Potent, and Selective α1-Adrenoceptor Ligands

Novel compounds characterized by a pyrrolo[3,2-d]pyrimidine-2,4-dione (PPm) system connected through an alkyl chain to a phenylpiperazine (PPz) residue were designed as structural analogues of the alpha(1)-adrenoceptor (alpha(1)-AR) ligand RN5 (1). In this new series of derivatives an arylpyrrolo moiety has replaced the indole nucleus of RN5. Several structural modifications were performed on the PPm and PPz moieties and the connecting alkyl chain. These compounds were synthesized and tested in radioligand binding experiments where many of them showed interesting binding profiles. Some compounds, including 31, 34, and 36, displayed substantial alpha(1)-AR selectivity with respect to serotoninergic 5-HT(1A) and dopaminergic D(1) and D(2) receptors. Two different molecular modeling approaches (pharmacophoric mapping and quantitative structure-affinity relationship analysis) have been applied to rationalize, at a quantitative level, the relationships between affinity toward alpha(1)-ARs and the structure of the studied compounds. Several QSAR models have been reported and described, accounting for the influence of various molecular portions on such affinity data.

Some pyrrole substituted aryl pyridazinone and phthalazinone derivatives and their antihypertensive activities

In this work, some 2-nonsubstituted/2-methyl-/2-(2-acetyloxyethyl)-6-[4-(substituted pyrrol-1-yl)phenyl]-4,5-dihydro-3(2H)-pyridazinone, derivatives and 2-nonsubstituted/2-methyl- 4-[4-(substituted pyrrol-1-yl)phenyl]-1(2H)-phthalazinone derivatives were synthesised by reacting hexan-2,5-dion or 1-aryl-3-carbethoxypent-1,4-diones with corresponding 2-substituted/nonsubstituted 6-(4'-aminophenyl)-4,5-dihydro-3(2H)-pyridazinone or 2-substituted/nonsubstituted-4-(4'-aminophenyl)-(2H)-phthalazinone under Paal-Knorr pyrrole synthesis conditions. The antihypertensive activities of the compounds were examined both in vitro and in vivo. Some pyridazinone derivatives showed appreciable activity.

Some pyridazinone and phthalazinone derivatives and their vasodilator activities

In this study, 6-[(4-arylidene-2-phenyl-5-oxoimidazolin-1-yl)phenyl]-4,5-dihydro-3(2H)-pyridazinone and 4-[(4-arylidene-2-phenyl-5-oxoimidazolin-1-yl)phenyl]-1(2H)-phthalazinone derivatives were synthesized by reacting 6-(4-aminophenyl)-4,5-dihydro-3(2H)-pyridazinone or 4-(4-aminophenyl)-1(2H)-phthalazinone compound with different 4-arylidene-2-phenyl-5(4H)-oxazolone derivatives. The vasodilator activities of the compounds were examined both in vitro and in vivo. Some pyridazinone derivatives showed appreciable activity.

Design, synthesis, and α1-adrenoceptor binding properties of new arylpiperazine derivatives bearing a flavone nucleus as the terminal heterocyclic molecular portion

Following our research project aimed at obtaining new compounds with high affinity and selectivity toward alpha(1)-adrenoceptors (AR), a new class of piperazine derivatives was designed, synthesized and biologically tested. The new compounds 1-13 are characterized by a flavone system linked, through an ethoxy or propoxy spacer, to a phenyl- or pyridazinone-piperazine moiety. Biological data showed an interesting profile for the phenylpiperazine subclass found to have a nanomolar affinity toward alpha(1)-AR, and less pronounced affinity for alpha(2)-AR and the 5-HT(1A) serotoninergic receptor. A discussion on the structure-activity relationship (SAR) of such compounds is also reported, on the basis of the flavone substitution pattern, length and functionalization of the spacer, and disruption of the phenylpiperazine system.