Microwave-Assisted Synthesis of Trazodone and Its Derivatives as New 5-HT1A Ligands: Binding and Docking Studies.

Trazodone, a well-known antidepressant drug widely used throughout the world, works as a 5-hydroxytryptamine (5-HT2) and α1-adrenergic receptor antagonist and a serotonin reuptake inhibitor. Our research aimed to develop a new method for the synthesis of trazodone and its derivatives. In the known methods of the synthesis of trazodone and its derivatives, organic and toxic solvents are used, and the synthesis time varies from several to several dozen hours. Our research shows that trazodone and its derivatives can be successfully obtained in the presence of potassium carbonate as a reaction medium in the microwave field in a few minutes. As a result of the research work, 17 derivatives of trazodone were obtained, including compounds that exhibit the characteristics of 5-HT1A receptor ligands. Molecular modeling studies were performed to understand the differences in the activity toward 5-HT1A and 5-HT2A receptors between ligand 10a (2-(6-(4-(3-chlorophenyl)piperazin-1-yl)hexyl)-[1,2,4]triazolo[4,3-a]pyridin-3(2H)-one) (5-HT1A Ki = 16 nM) and trazodone. The docking results indicate the lack of the binding of ligand 10a to 5-HT2AR, which is consistent with the in vitro studies. On the other hand, the docking results for the 5-HT1A receptor indicate two possible binding modes. Crystallographic studies support the hypothesis of an extended conformation.

Design, synthesis and cardiovascular evaluation of some aminoisopropanoloxy derivatives of xanthone.

A series of aminoisopropanoloxy derivatives of xanthone has been synthesized and their pharmacological properties regarding the cardiovascular system has been evaluated. Radioligand binding and functional studies in isolated organs revealed that title compounds present high affinity and antagonistic potency for α1-(compound 2 and 8), ß-(compounds 1, 3, 4, 7), α1/ß-(compounds 5 and 6) adrenoceptors. Furthermore, compound 7, the structural analogue of verapamil, possesses calcium entry blocking activity. The title compounds showed hypotensive and antiarrhythmic properties due to their adrenoceptor blocking effect. Moreover, they did not affect QRS and QT intervals, and they did not have proarrhythmic potential at tested doses. In addition they exerted anti-aggregation effect. The results of this study suggest that new compounds with multidirectional activity in cardiovascular system might be found in the group of xanthone derivatives.

Design, synthesis, crystal structure, biological evaluation and molecular docking studies of carbazole-arylpiperazine derivatives.

Subtype-selective α1-adrenoceptor (AR) antagonists display optimum therapeutic efficacies for the treatment of benign prostatic hyperplasia (BPH). In this study, we designed and synthesized novel carbazole-arylpiperazines derivatives (1 and 2) on the basis of the proposed pharmacophore model for α1-AR antagonists. Structural properties were investigated using single-crystal X-ray diffraction analysis. Comparison of crystal structures with ligand-based pharmacophore models revealed that the two agents may possess antagonistic effects on α1D subtype. Tissue functional assay in vitro showed that compound 2 exerted strong antagonistic activity on α1B-AR (pA2 7.13) with a poor selectivity for α1A and α1D subtypes. Compound 1 exhibited enhanced antagonistic effect on α1D subtype (pA2 7.06) and excellent selectivity for α1D over α1B (α1D/α1B ratio=79.4). To illustrate the relationship between antagonistic activity and chemical structure, molecular docking studies were performed using the homology models of α1 receptors. Binding mechanism indicated that small hydrophobic substituents attached to the arylpiperazine moiety were essential for rational design of α1D-selective antagonists.

Synthesis and adrenolytic activity of new propanolamines.

The synthesis of (2R,S)-1-(6-methoxy-4-(methoxymethyl)-1H-indol-5-yloxy)-3-(2-(2-methoxyphenoxy)ethylamino)propan-2-ol and (2R,S)-1-(4-methoxy-6-(methoxymethyl)-1H-indol-5-yloxy)-3-(2-(2-methoxyphenoxy)ethylamino)propan-2-ol is described. The compounds were tested for electrographic, antiarrhythmic, hypotensive, and spasmolytic activity, as well as for alpha(1)-, alpha(2)- and beta(1)-adrenoceptor binding affinity.

Design, synthesis and pharmacological screening of novel antihypertensive agents using hybrid approach.

Eight derivatives of general formula 2-(2-(4-(3-((5-substituted methylene)-4-oxo-2-(phenylimino)thiazolidin-3-yl)-2-hydroxypropylamino)benzoyl)hydrazinyl)-2-oxoethyl nitrate were synthesized and tested for electrocardiographic, antiarrhythmic, vasorelaxing and antihypertensive activity as well as for in-vitro nitric oxide (NO) releasing ability. Compound 8b 2-(2-(4-(3-(5-benzyliden-4-oxo-2-(phenylimino)thiazolidin-3-yl)-2-hydroxypropylamino)benzoyl)hydrazinyl)-2-oxoethyl nitrate, was the most potent in this series. The pharmacological results suggested that the antiarrhythmic effects of these compounds were related to their adrenolytic properties which are believed to be due to the presence of the 5-(substituted)methylen-2-(phenylimino)thiazolidin-4-one moiety with less bulky, electron donating substituent on the phenyl ring at 5th position of the thiazolidin-4-one. In conclusion, most of the synthesized compounds were significantly potent as antiarrhythmic and antihypertensive; this might be due to the presence of different pharmacopores which might act at different locations with different mode of action. Further insights of the same can be obtained by doing investigation at receptor level. The potency of compounds 8a-8h were promising enough to continue further experiments.

Stereospecific effects of benzo[d]isothiazolyloxypropanolamine derivatives at beta-adrenoceptors: synthesis, chiral resolution, and biological activity in vitro.

We performed the asymmetric synthesis of four enantiopure benzo[d] isothiazo-3-or 5-yloxypropanolamine derivatives, previously described as competitive antagonists at beta-adrenoceptors. The chemical characterization of each enantiomer was accomplished by (1)H NMR and HPLC/DAD/CD. The direct chromatographic separation of the enantiomers via chiral HPLC was investigated. The best resolutions were achieved using cellulose tris (3,5-dimethylphenyl carbamate) (Chiralcel OD-H) and amylose tris (3,5-dimethylphenyl carbamate) (Chiralpak AD). The enantiomers obtained had enantiomeric purities suitable for biological assays. Tested in isolated rat cardiac and intestinal tissues to evaluate their effects at beta(1)- and beta(3)-adrenoceptors, the (S)-enantiomers revealed a higher degree of antagonism than (R)-enantiomers at both subtypes, even though their activity was greater at the cardiac beta(1)-subtype. The potent and cardiospecific antagonistic effect exerted by the compounds tested suggests that the benzisothiazole moiety could be an interesting scaffold for discovering new chiral beta-blocking drugs.

Design and synthesis of aryloxypropanolamine as ß3-adrenergic receptor antagonist in cancer and lipolysis.

ß-adrenergic receptors (ß-ARs) are broadly distributed in various tissues and regulate a panel of important physiological functions and disease states including cancer. Above all, ß3-adrenergic receptor (ß3-AR) plays a significant role in regulating lipolysis and thermogenesis in adipose tissue. In this study, we designed and synthesized a series of novel L-748,337 derivatives as selective human ß3-AR antagonists. Among all the tested L-748,337 analogs, compound 23d was found to display 23-fold more potent ß3-AR antagonist activity (EC50 = 0.5117 nM) than L-748,337 (EC50 = 11.91 nM). In vivo, compound 23d could alleviate weight loss and inhibit tumor growth in C26 tumor cachexia animal model.

Novel adrenoceptor antagonists with a tricyclic pyrrolodipyridazine skeleton.

A still unknown tricyclic heterocyclic system (5) was synthesized from 6-hydroxy-2-methylpyridazin-3-one and its structure identified as 2,8-dichloro-6-methylpyrrolo[1,2-b:3,4-d']dipyridazin-5(6H)- one by spectroscopic investigations. Selective condensation of 5 with 2-[4-(2-substituted-phenyl)piperazin-1-yl]ethylamine gave the 2-arylpiperazinylethylamino-8-chloro derivatives 6a-c, which were investigated in binding studies toward the three alpha1-adrenergic and 5-HT1A-serotonergic receptor subtypes. They displayed high potency on all the assays and some selectivity for alpha1a and alpha1d subtypes.

α1-Adrenoceptor and serotonin 5-HT(1A) receptor affinity of homobivalent 4-aminoquinoline compounds: an investigation of the effect of linker length.

α1-adrenoceptor (α1-AR) subtype-selective ligands lacking off-target affinity for the 5-HT(1A) receptor (5-HT(1A)-R) will provide therapeutic benefits in the treatment of urogenital conditions such as benign prostatic hyperplasia. In this study we determined the affinity of 4-aminoquinoline and eleven homobivalent 4-aminoquinoline ligands (diquinolines) with alkane linkers of 2-12 atoms (C2-C12) for α(1A), α(1B) and α(1D)-ARs and the 5-HT(1A)-R. These ligands are α(1A)-AR antagonists with nanomolar affinity for α(1A) and α(1B)-ARs. They display linker-length dependent selectivity for α(1A/B)-ARs over α(1D)-AR and the 5-HT(1A)-R. The C2 diquinoline has the highest affinity for α1A-AR (pKi 7.60±0.26) and greater than 30-fold and 600-fold selectivity for α(1A)-AR over α(1D)-AR and 5-HT(1A)-R respectively. A decrease in affinity for α1-ARs is observed as the linker length increases, reaching a nadir at 5 (α(1A/1B)-ARs) or 6 (α(1D)-AR) atoms; after which affinity increases as the linker is lengthened, peaking at 9 (α(1A/1B/1D)-ARs) or 8 (5-HT(1A)-R) atoms. Docking studies suggest that 4-aminoquinoline and C2 bind within the orthosteric binding site, while for C9 one end is situated within the orthosteric binding pocket, while the other 4-aminoquinoline moiety interacts with the extracellular surface. The limited α(1D)-AR and 5-HT(1A)-R affinity of these compounds makes them promising leads for future drug development of α(1A)-AR selective ligands without α(1D)-AR and the 5-HT(1A)-R off-target activity.

Synthesis and adrenolytic activity of 1-(1H-indol-4-yloxy)-3-(2-(2-methoxy phenoxy)ethylamino)propan-2-ol analogs and its enantiomers. Part 2.

The synthesis of (2RS)-1-(5-methoxy-1H-indol-4-yloxy)-3-(2-(2-methoxyphenoxy)ethylamino)propan-2-ol and (2RS)-1-(7-methoxy-1H-indol-4-yloxy)-3-(2-(2-methoxyphenoxy)ethylamino)propan-2-ol and its enantiomers, analogs of 1-(1H-indol-4-yloxy)-3-(2-(2-methoxyphenoxy)ethylamino)propan-2-ol ((RS)-9) is described. Compounds were tested for electrographic, antiarrhythmic, hypotensive and spasmolytic activities as well as for alpha(1)-, alpha(2)- and beta(1)-adrenoceptors binding affinities. The antagonist potency of the new compounds was compared with carvedilol and (RS)-9.

Synthesis and adrenolytic activity of 1-(1H-indol-4-yloxy)-3-{[2-(2-methoxyphenoxy)ethyl]amino}propan-2-ol and its enantiomers. Part 1.

The synthesis of (2RS)-1-(1H-indol-4-yloxy)-3-{[2-(2-methoxyphenoxy)ethyl]amino}propan-2-ol ((RS)-9) and its enantiomers has been described and tested for electrocardiographic, antiarrhythmic, hypotensive and spasmolytic activities as well as for alpha(1)-, alpha(2)- and beta(1)-adrenoceptors' binding affinities. All compounds significantly decrease systolic and diastolic blood pressure, and possess antiarrhythmic activity and affinity to alpha(1)-, alpha(2)- and beta(1)-adrenoceptors. The results suggest that the antiarrhythmic and hypotensive effects of these compounds are related to their adrenolytic but not spasmolytic properties.

Design, synthesis and pharmacological evaluation of new 1-[3-(4-arylpiperazin-1-yl)-2-hydroxy-propyl]-3,3-diphenylpyrrolidin-2-one derivatives with antiarrhythmic, antihypertensive, and alpha-adrenolytic activity.

A series of novel arylpiperazines bearing a 3,3-diphenylpyrrolidin-2-one fragment were synthesized and evaluated for their binding affinity for alpha(1)- and alpha(2)-adrenoceptors (ARs), as well as their antiarrhythmic, and antihypertensive activities. The highest affinity for the alpha(1)-AR was displayed by 1-{3-[4-(2-ethoxy-phenyl)-piperazin-1-yl]-2-hydroxy-propyl}-3,3-diphenylpyrrolidin-2-one (7), which binds with a pK(i)=7.28. The highest affinity for the alpha(2)-AR was shown by 1-{3-[4-(2-methoxy-phenyl)-piperazin-1-yl]-2-hydroxy-propyl}-3,3-diphenylpyrrolidin-2-one (5), which binds with a pK(i)=6.68. Compound 7 was additionally evaluated in in vitro functional tests for its affinity for alpha(1B)- and alpha(1D)-AR, which gave pA(2) alpha(1B)=6.55 and pA(2) alpha(1D)=7.26. Among the compounds tested, compound 7 also had the highest prophylactic antiarrhythmic activity in adrenaline-induced arrhythmia in anaesthetized rats. Its ED(50) value was 1.1mg/kg (i.v.). The compounds significantly decreased systolic and diastolic pressure in normotensive anaesthetized rats at doses of 2.5-5.0mg/kg (i.v.) and their hypotensive effects lasted for longer than 1h. It was found that the introduction of two phenyl ring substituents into the 3rd position of the pyrrolidin-2-one fragment gave compounds with affinity for both alpha(1)- and alpha(2)-AR. The substitution of the 2nd position in the phenyl piperazinyl fragment of the molecule was crucial for activity. To determine detailed information concerning the structure-activity relationship, a preliminary molecular modeling study was undertaken.

Design and synthesis of an alpha1a-adrenergic receptor subtype-selective antagonist from BE2254.

An alpha1a-adrenoceptor-selective antagonist has the potential to be a new benign prostatic hyperplasia drug with reduced side-effects. Modification of the non-selective antagonist BE2254 led to the development of a series of tetralin analogs. Evaluation of these compounds in cloned human alpha1-adrenoceptors resulted in the discovery of an analog that showed selectivity toward the human alpha1a-adrenergic receptor subtype. The compound also showed moderate potency to block human prostate muscle contraction.

Palladium-catalyzed synthesis of 2,3-dihydro-2-ylidene-1,4-benzodioxins.

Palladium-catalyzed condensation of benzene-1,2-diol with various propargylic carbonates afforded regio- and stereoselectively 2,3-dihydro-2-ylidene-1,4-benzodioxins. The reaction is suggested to proceed by the formation of a (sigma-allenyl)palladium complex, followed by the intermolecular attack of the phenoxide ion on this complex to generate a new (sigma-allyl)palladium complex in equilibrium with the corresponding (eta(3)-allyl)palladium complex. Intramolecular attack of the phenoxide ion afforded the corresponding benzodioxan compound. This last attack occurs predominantly at the more electrophilic end of the (eta(3)-allyl)palladium intermediate. The Z- or E-stereochemistry of the products was established by (1)H NMR and proton NOE measurements and also by X-ray analysis on an example. The Z-stereochemistry generally observed is in agreement with the formation of this (eta(3)-allyl)palladium intermediate. However, in the case of tertiary propargylic carbonates, the E-stereochemistry generally observed could be explained by an intramolecular attack of the phenoxide ion on the intermediate (sigma-allyl)palladium complex, in slow equilibrium with the (eta(3)-allyl)palladium complex.

The use of high-throughput synthesis and purification in the preparation of a directed library of adrenergic agents.

A library of potential agonists and antagonists for adrenergic receptors was prepared using high-throughput solution-phase parallel synthesis. Traditional solution-phase reductive amination reactions followed by rapid purification by ion exchange chromatography yielded products with near-analytical purity. An array of ketones and amines, arranged in an 8 x 12 matrix, were combined to form 96 individual compounds.

Arylpiperazine substituted heterocycles as selective alpha(1a) adrenergic antagonists.

Antagonists of the alpha(1)-adrenergic receptors (alpha(1)-ARs) are useful for the treatment of benign prostatic hyperplasia. A series of potent and subtype-selective alpha(1a)-AR antagonists has been synthesized, displaying in vitro binding affinity in the low the nanomolar range.

Kinetic resolution of 1-chloro-3-(1-naphthyloxy)-2-propanol, an intermediate in the synthesis of beta-adrenergic receptor blockers.

(R)- and (S)-1-chloro-3-(1-naphthyloxy)-2-propanol are intermediates in the synthesis of beta-adrenergic blocking agents and antihypertensive drugs such as propranolol and nadoxolol. Herein, improvement in the preparation of racemic 1-chloro-3-(1-naphthyloxy)-2-propanol generated from 1-naphthol and epichlorohydrin are reported. In addition, kinetic resolution studies have been conducted to obtain both (R) and (S)-1-chloro-3-(1-naphthyloxy)-2-propanol. These compounds were obtained in highly optically pure form by the stereoselective hydrolysis of its acyl derivatives using whole cell preparations containing enzymes from native sources. The results were compared with those obtained using commercial lipases.

Synthesis of 3a,4-dihydro-3H-[1]benzopyrano[4,3-c]isoxazoles, displaying combined 5-HT uptake inhibiting and alpha2-adrenoceptor antagonistic activities. Part 2: Further exploration on the cinnamyl moiety.

In our previous paper we have described the synthesis of a series of 3-piperazinylmethyl-3a,4-dihydro-3H-[1]benzopyrano[4,3-c]isoxazoles, as novel dual 5-HT reuptake inhibitors and alpha2-adrenoceptor antagonists. That investigation led to the identification of the cinnamyl fragment as the most suitable moiety for combined activity. This paper outlines a further optimisation programme, focused on the exploration of the aromatic ring present on the cinnamyl moiety of compounds 1, 2 and 3.

Design and synthesis of novel dihydropyridine alpha-1a antagonists.

A series of analogs of SNAP 5150 containing heteroatoms at C2 or C6 positions is described. Herein, we report that the presence of alkyl substituted heteroatoms at the C2(6)-positions of the dihydropyridine are well tolerated. In addition, 15 inhibited the phenylephrine induced contraction of dog prostate tissue with a Kb of 1.5 nM and showed a Kb (DBP, dogs, microg/kg)/Kb (IUP, dogs, microg/kg) ratio of 14.8/2.5.

The new generation dihydropyridine type calcium blockers, bearing 4-phenyl oxypropanolamine, display alpha-/beta-adrenoceptor antagonist and long-acting antihypertensive activities.

A new series of dihydropyridine derivatives, bearing oxypropanolamine moiety on phenyl ring at the 4-position of the dihydropyridine base, were prepared. Oxypropanolamine was synthesized by replacing the phenolic OH of vanillin or other compounds, having a phenyl aldehyde group, with epichlorohydrin, followed by cleavaging the obtained epoxide compounds with tert-butylamine, n-butylamine or 2-methoxy-1-oxyethylamino benzene (guaiacoxyethylamine), respectively. Obtained various oxypropanolamine compounds, still remaining a phenyl aldehyde moiety, were then performed by Hantzsch condensation reaction with methylacetoacetate or ethylacetoacetate, respectively, to give our new series of dihydropyridine linked with the 4-phenyl ring. These compounds were evaluated for inotropic, chronotropic, and aorta contractility that associated with calcium channel and adrenoceptor antagonist activities. Dihydropyridine derivatives that with oxypropanolamine side chain on their 4-phenyl ring associated alpha-/beta-adrenoceptor blocking activities created a new family of calcium entry and the third generation beta-adrenoceptor blockers. Optimizing this research to obtain more potent alpha-/beta-adrenoceptor blocking and long-acting antihypertensive oxypropanolamine on the 4-phenyl ring of dihydropyridine series compounds was thus accomplished and classified as third generation dihydropyridine type calcium channel blockers, in comparison with previous short-acting type nifedipine and long-acting type amlodipine. We concluded that compounds 1a, 1b and 1g showed not only markedly high calcium-antagonistic activity but also the highest antihypertensive effect; compounds 1b, 1c, 1f, 1g, 1i and 1j induced sustained antihypertensive effects are major and attributed to their calcium entry and alpha-adrenoceptor blocking activities in the blood vessel due to their introduction of 2-methoxy, 1-oxyethylamino benzene moiety in the side chain on the 4-phenyl ring of dihydropyridine. Bradycardiac effects of all the compounds 1a-1j resulted from calcium entry and beta-adrenoceptor blocking, which attenuate the sympathetic activation-associated reflex tachycardia in the heart. We selected compound 1b as candidate compound for further pharmacological and pre-clinical evaluation studies.