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Background/aims: The NMDA receptor plays a key role in the pathogenesis of neurodegenerative disorders including Alzheimer's and Huntington's disease, as well as depression and drug or alcohol dependence. Due to its participation in these pathologies, the development of selective modulators for this ion channel is a promising strategy for rational drug therapy. The prototypical negative allosteric modulator ifenprodil inhibits selectively GluN2B subunit containing NMDA receptors. It was conformationally restricted as 2-methyl-3-(4-phenylbutyl)-2,3,4,5-tetrahydro-1H-3-benzazepine-1,7-diol, which showed high GluN2B affinity and inhibitory activity. For a better understanding of the relevance of the functional groups and structural elements, the substituents of this 3-benzazepine were removed successively (deconstruction). Then, additional structural elements were introduced (reconstruction) with the aim to analyze, which additional modifications were tolerated by the GluN2B receptor., Methods: The GluN2B affinity was recorded in radioligand receptor binding studies with the radioligand [ 3 H]ifenprodil. The activity of the ligands was determined in two-electrode voltage clamp experiments using Xenopus laevis oocytes transfected with cRNA encoding the GluN1-1a and GluN2B subunits of the NMDA receptor. Docking studies showed the crucial interactions with the NMDA receptor protein., Results: The deconstruction approach showed that removal of the methyl moiety and the phenolic OH moiety in 7-positon resulted in almost the same GluN2B affinity as the parent 3-benzazepine. A considerably reduced GluN2B affinity was found for the 3-benzazepine without further substituents. However, removal of one or both OH moieties led to considerably reduced NMDA receptor inhibition. Introduction of a NO 2 moiety or bioisosteric replacement of the phenol by a benzoxazolone resulted in comparable GluN2B affinity, but almost complete loss of inhibitory activity. An O-atom, a carbonyl moiety or a F-atom in the tetramethylene spacer led to 6-7-fold reduced ion channel inhibition., Conclusion: The results reveal an uncoupling of affinity and activity for the tested 3-benzazepines. Strong inhibition of [ 3 H]ifenprodil binding by a test compound does not necessarily translate into strong inhibition of the ion flux through the NMDA receptor associated ion channel. 3-(4-Phenylbutyl)-2,3,4,5-tetrahydro-1H-3-benzazepine- 1,7-diol (WMS-1410) shows high GluN2B affinity and strong inhibition of the ion channel. Deconstruction by removal of one or both OH moieties reduced the inhibitory activity proving the importance of the OH groups for ion channel blockade. Reconstruction by introduction of various structural elements into the left benzene ring or into the tetramethylene spacer reduced the NMDA receptor inhibition. It can be concluded that these modifications are not able to translate binding into inhibition., Competing Interests: The authors have no conflicts of interest to declare., (© Copyright by the Author(s). Published by Cell Physiol Biochem Press.)

Novel 4-(4-bromophenyl)phthalazine derivatives connected via an alkyl spacer to amine or N-substituted piperazine were designed and synthesized as promising α-adrenoceptor antagonists. The structures of the phthalazine derivatives were established using elemental and spectral analyses. Twelve of the tested compounds displayed significant α-blocking activity. Molecular modeling studies were performed to rationalize the biological results. Among the tested compounds, 7j displayed the best-fitting score and the highest in vitro activity.

A series of 2-[(heteroaryl)methyl]imidazolines was synthesized and tested for their activities at α(1)- and α(2)-adrenoceptors and imidazoline I(1) and I(2) receptors. The most active 2-[(indazol-1-yl)methyl]imidazolines showed high or moderate affinities for α(1)- and α(2)-adrenoceptors. However, their intrinsic activities at α(2A)-adrenoceptors proved to be negligible. A selected 7-chloro derivative behaved as a potent α(1)-adrenoceptor antagonist and exhibited peripherally mediated hypotensive effects in rats., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

We report the discovery of a new family of α(2) adrenergic receptor antagonists derived from atipamezole. Affinities of the compounds at human α(2) and α(1b) receptors as well as their functional activities at hα(2A) receptors were determined in competition binding and G-protein activation assays, respectively. Central α(2) antagonist activities were confirmed in mice after oral administration. Further studies on a selected example: (+)-4-(1a,6-dihydro-1H-cyclopropa[a]inden-6a-yl)-1H-imidazole, (+)-1 (F 14805), were undertaken to probe the potential of the series. On the one hand, (+)-1 increased the release of noradrenaline in mouse frontal cortex following acute systemic administration, the magnitude of this effect being much larger than that obtained with reference agents. On the other, (+)-1 produced minimal cardiovascular effects in intact, anesthetized rat, a surprising outcome that might be explained by its differential action at peripheral and central α(2) receptors. A strategy for improving the therapeutic window of α(2) antagonists is put forward.

Syntheses, biological evaluation, and structure-activity relationships for a series of novel 5-styryl and 5-phenethyl analogs of dimebolin are disclosed. The novel derivatives and dimebolin share a broad spectrum of activities against therapeutically relevant targets. Among all synthesized derivatives, 2,8-dimethyl-5-[(Z)-2-phenylvinyl]-2,3,4,5-tetrahydro-1H-pyrido[4,3-b]indole and its 5-phenethyl analog are the most potent blockers of 5-HT(7), 5-HT(6), 5-HT(2C), Adrenergic alpha(2) and H(1) receptors. The general affinity rank order towards the studied receptors was Z-3(2)>4(2)4(3)>>dimebolin, all of them having highest affinities to 5-HT(7) receptors., (Copyright 2009 Elsevier Ltd. All rights reserved.)

2,3-dihydrobenzo[b][1,4]oxathiine represents a valuable pharmacophoric heterocyclic nucleus known since very long time. Initially, together with some patents reporting the use of these compounds as herbicides or lipogenesis inhibitors, several papers reported their ability as melatonin, histamine and serotonin receptor ligands, alpha-adrenoreceptor blockers as well as non-glycoside sweeteners. This wide range of biological activities has been recently further improved by studies stating their activity as antimycotics, multi-defense antioxidants and estrogen receptor ligands. The last insights regarding the preparation, the biological activity and the structure activity relationship (SAR) of derivatives containing the dihydrobenzoxathiine skeleton will be discussed in this review.

Doxazosin analogues 1-3 and 1a were synthesized and investigated at alpha1-adrenoceptors and PC-3, DU-145, and LNCaP human prostate cancer cells. Compound 1 (cyclodoxazosin) was a potent alpha(1B)-adrenoceptor antagonist displaying antiproliferative activity higher than that of doxazosin in cancer cells in vitro and in vivo, respectively. Because of its antitumor efficacy at low concentrations, lower apoptotic activity in NHDF vs tumor cells, and antiangiogenetic effect, 1 showed a better therapeutic profile relative to doxazosin.

Conformational restriction of naftopidil proved to be compatible with binding at alpha(1) adrenoceptor subtypes and 5-HT receptor 1A (5-HT(1A)), and led to the discovery of a new class of ligands with a 1,3-dioxolane (1,3-oxathiolane, 1,3-dithiolane) structure. Compound 7 shows the highest affinity toward alpha(1a) and alpha(1d) adrenoceptor subtypes (pK(i) alpha(1a) = 9.58, pK(i) alpha(1d) = 9.09) and selectivity over 5-HT(1A) receptors (alpha(1a)/5-HT(1A) = 100, alpha(1d)/5-HT(1A) = 26). In functional experiments it behaves as a potent competitive alpha(1a) and alpha(1d) adrenoceptor antagonist (pK(b) alpha(1A) = 8.24, pK(b) alpha(1D) = 8.14), whereas at 5-HT(1A) receptors it is a potent partial agonist (pD(2) = 8.30). Compounds 8 and 10 display high affinity (pK(i) = 8.29 and 8.26, respectively) and selectivity for 5-HT(1A) (5-HT(1A)/alpha(1) = 18 and 10). In functional experiments at the 5-HT(1A) receptor, compound 8 appears to be neutral antagonist (pK(b) = 7.29), whereas compound 10 is a partial agonist (pD(2) = 6.27). Therefore, 1,3-dioxolane-based ligands are a versatile class of compounds useful for the development of more selective ligands for one (alpha(1)) or the other (5-HT(1A)) receptor system.

A series of phenoxyisoquinolines, N-phenoxyethyl-1-(2-nitrophenyl)-1,2,3,4-THIQs 3a-3d, N-phenoxyethyl-1-benzyl-1,2,3,4-THIQ 3e, N-phenoxyethyl-1-(2-aminophenyl)-1,2,3,4-THIQs 5f-5i, N-phenoxyethyl-1-(2-phenoxyethylaminophenyl)-1,2,3,4-THIQs 5f'-5i', have been synthesized and tested in isolated rat vas deferens alpha-adrenoreceptors. Comparison of pA2 values for these compounds in the presence of phenylephrine confirms that alpha(1)-adrenoceptor blocking activity of 3a-3d (-NO(2) series) is more active than 6a-6c (-NH(2) series) in the aortic rings isolated from SD rats. On the other hand, the electron-donating group at the 6-position of isoquinoline ring either increases or decreases the alpha(1)-adrenoceptor blocking activity.

The medicine called Tamsulosin was produced 25 years ago and since then almost 10 new synthesis route has been known. Each process shows the researchers' workstyle, every year, which mainly differs in the way of separating the enantiomers. The applied reaction steps also reflect the development over the past 25 years and the new synthesis is influenced by the antecedents. The key-intermediate used in our new method is a racemic secondary amine derivative, which is unknown in the literature before and for resolving it, we worked out a quite advantegeous process. By using an optically active secondary amine, side reactions can be avoided., ((c) 2008 Wiley-Liss, Inc.)

To prepare thiol-reactive ifenprodil derivatives designed as potential probes for cysteine-substituted NR2B containing NMDA receptors, electrophilic centers were introduced in different areas of the ifenprodil structure. Intermediates and final compounds were evaluated by binding studies and by electrophysiology to determine the structural requirements for their selectivity. The reactive compounds were further tested for their stability and for their reactivity in model reactions; some were found suitable as structural probes to investigate the binding site and the docking mode of ifenprodil in the NR2B subunit.

Benign prostatic hyperplasia/lower urinary tract symptoms (BPH/LUTS) can be effectively treated by alpha(1) adrenergic receptor antagonists, but these drugs also produce side effects that are related to their subtype non-selective nature. To overcome this limitation, it was hypothesized that an alpha(1a/1d) subtype-selective antagonist would be efficacious while keeping side effects to a minimum. To discover alpha(1a/1d)-selective antagonists and improve metabolic stability of our previously reported compounds, we have designed and synthesized a series of (phenylpiperazinyl)- or (phenylpiperidinyl)-cyclohexylsulfonamides. By incorporating the information obtained from metabolism studies, we were able to discover several compounds that are both alpha(1a/1d) adrenoceptor subtype selective and show increased stability toward human liver microsomal metabolism. The selectivity profile of these compounds provides great improvement over the commercial drug tamsulosin, hence may pave the way to the development of new and efficacious therapeutic agents with reduced side effects.

An on-line SPE-HPLC method, using a monolithic poly(glycidyl methacrylate-co-ethylene glycol dimethacrylate) (poly(GMA-EDMA)) based weak cation-exchange (WCX) column, was developed for simultaneous determination of alpha1-adrenergic receptor antagonists in human plasma. The monolithic WCX column was prepared by an in-situ polymerization protocol and modified stepwise with ethylenediamine and chloroacetic acid. On connecting this column to an injection valve, an on-line SPE protocol could be established for removal of matrices (mainly proteins and lipids) and preconcentration of four alpha1-adrenergic receptor antagonists in human plasma. This method was validated and then used for determination of terazosin, alfuzosin, prazosin, and doxazosin in clinical plasma samples. For all analytes, each calibration curve was found to be linear over a range of 0.005-5 microg/mL (R>0.997), and the limit of detection for each analyte was 0.5 ng/mL. Recovery (>80%) and precision (RSD<15%) for inter- and intra-day assay were tested at three concentration levels of each analyte and showed acceptable results for quantitative assay. Real samples from hypertensive patients were monitored and results were in agreement with those of the conventional liquid-liquid extraction-HPLC method. Furthermore, due to its good permeability and biocompatibility, the monolithic WCX sorbent could be reused more than 300 times. The proposed method was especially appropriate for multi-analyte monitoring in plasma samples.

In the present report, a novel series of 1-indanone alpha(1)-adrenoceptor antagonists were designed and synthesized based on 3D-pharmacophore model. Their in vitro alpha(1)-adrenoceptor antagonistic assay showed that three compounds (2a, 2m, and 2o) had similar or improved alpha(1)-adrenoceptor antagonistic activities relative to the positive control prazosin. Based on these results, a three-dimensional quantitative structure-activity relationship study was performed using a Self-Organizing Molecular Field Analysis method to provide insight for the future development of alpha(1)-adrenoceptor antagonists.

The efficient preparation and pharmacological characterization of different families of (bis)guanidine and (bis)2-aminoimidazoline derivatives ("twin" and "half" molecules) as potential alpha(2)-adrenoceptor antagonists for the treatment of depression is presented. The affinity toward the alpha(2)-adrenoceptor of all the compounds prepared was measured in vitro in human brain tissue. Additionally, the activity as agonist or antagonist of those compounds with a pK(i) larger than 7 was determined in functional [(35)S]GTPgammaS binding assays in human brain tissue. Finally, the activity of the most promising compounds was confirmed by means of in vivo microdialysis experiments in rats. Compounds 1, 2b, 3b, 12b, 13b, 17b, 18b, 22b, 25b, 26b, 28b, and 30 showed a good affinity toward the alpha(2)-ARs. In general, the 2-aminoimidazoline derivatives displayed higher affinities than their guanidine analogues. Finally and most importantly, compounds 18b and 26b showed antagonistic properties over alpha(2)-ARs not only in vitro [(35)S]GTPgammaS binding but also in vivo microdialysis experiments. Moreover, both compounds have shown to be able to cross the blood-brain barrier and, therefore, they can be considered as potential antidepressants.

Benign Prostatic Hyperplasia/Lower Urinary Tract Symptoms (BPH/LUTS) can be effectively treated by alpha(1)-adrenergic receptor antagonists. Unfortunately, all currently marketed alpha(1) blockers produced CV related side effects that are caused by the subtype non-selective nature of the drugs. To overcome this problem, it was postulated that a alpha(1a/1d) subtype selective antagonist would bring more benefit for the treatment of BPH/LUTS. In developing selective alpha(1a/1d) ligands, (arylpiperazinyl)cyclohexylsulfonamides were synthesized and their binding profiles against three cloned human alpha(1)-adrenergic receptor subtypes were evaluated. Many compounds show equal affinity for both alpha(1a) and alpha(1d) subtypes with good selectivity against the alpha(1b) subtype. They also overcome the problem of dopamine receptor affinity that previous analogues had exhibited.

The synthesis of a series of 4-(6,7-dimethoxy-1,2,3,4-tetrahydroisoquinolin-2-yl)methyl-2-arylbenzofuran and 4-(6,7-dimethoxy-1,2,3,4-tetrahydroisoquinolin-2-yl)methylbenzofuran-2-carboxamide derivatives as novel alpha(2C)-adrenergic receptor antagonists are described. Their affinity at three different human alpha(2)-adrenergic receptors is reported, and some of these compounds exhibited high affinity for the alpha(2C)-adrenergic receptor with high subtype selectivity. Among them, compound 10e has been found to show the anti-L-dopa-induced dyskinetic activity in marmosets. The structure-activity relationship of these compounds is also discussed.

alpha(1)-Adrenoceptor selective antagonists are crucial in investigating the role and biological functions of alpha(1)-adrenoceptor subtypes. We synthesized and studied the alpha(1)-adrenoceptor blocking properties of new molecules structurally related to the alpha(1B)-adrenoceptor selective antagonist (+)-cyclazosin, in an attempt to improve its receptor selectivity. In particular, we investigated the importance of substituents introduced at position 5 of the 2-furan moiety of (+)-cyclazosin and its replacement with classical isosteric rings. The 5-methylfuryl derivative (+)-3, [(+)-metcyclazosin], improved the pharmacological properties of the progenitor, displaying a competitive antagonism and an 11 fold increased selectivity for alpha(1B) over alpha(1A), while maintaining a similar selectivity for the alpha(1B)-adrenoceptor relative to the alpha(1D)-adrenoceptor. Compound (+)-3 may represent a useful tool for alpha(1B)-adrenoceptor characterization in functional studies.

Subtype-selective alpha-1a and/or alpha-1d adrenergic receptor antagonists may be useful for the treatment of benign prostatic hyperplasia (BPH) and lower urinary tract symptoms (LUTS) with fewer adverse effects than non-selective drugs. A series of 1-arylpiperazinyl-4-cyclohexylamine derived isoindole-1,3-diones has been synthesized, displaying in vitro alpha(1a) and alpha(1d) binding affinity K(i) values in the range of 0.09-38nM with K(i)(alpha1b)/K(i)(alpha1a) and K(i)(alpha1b)/K(i)(alpha1d) selectivity ratios up to 3607-fold.

Starting from two acridine compounds identified in a high-throughput screening campaign (1 and 2, Table 1), a series of 4-aminoquinolines was synthesized and tested for their properties on the human alpha(2)-adrenoceptor subtypes (alpha(2A), alpha(2B), and alpha(2C)). A number of compounds with good antagonist potencies against the alpha(2C)-adrenoceptor and excellent subtype selectivities over the other two subtypes were discovered. For example, (R)-{4-[4-(3,4-dimethylpiperazin-1-yl)phenylamino]quinolin-3-yl}methanol 6j had an antagonist potency of 8.5 nM against, and a subtype selectivity of more than 200-fold for, the alpha(2C)-adrenoceptor. Investigation of the structure-activity relationship identified a number of structural features, the most critical of which was an absolute need for a substituent in the 3-position of the quinoline ring. The 3-position on the piperazine ring was also found to play an appreciable role, as substitutions in that position exerted a significant and stereospecific beneficial effect on the alpha(2C)-adrenoceptor affinity and potency. Replacing the piperazine ring proved difficult, with 1,4-diazepanes representing the only viable alternative.

A series of novel indolylpiperidine derivatives were synthesized and assessed for their pharmacological profiles at alpha1 adrenoceptor subtypes by in vitro binding studies at rat alpha1A and alpha1B receptors. Compound 11 was a potent (Ki=0.63 nM) and selective (approximately 30-fold more selective for the alpha1B receptor than for the alpha1A receptor) alpha1B adrenoceptor antagonist.

With the aim to develop new ligands able to discriminate among the three subtypes of alpha1-adrenergic receptors (alpha1A-AR, alpha1B-AR, and alpha1D-AR), a series of new 1,2,3,9-tetrahydro-4H-carbazol-4-ones bearing a 3-[[[2-(4-hydroxyphenyl)ethyl]amino]methyl] or a 3-[[4-(2-substitutedphenyl)piperazin-1-yl]methyl] side chain were synthesized. The general structure of the new compounds is reminiscent of HEAT and RN5, two potent alpha1-AR antagonists which show high affinities for all three alpha1-AR subtypes. Some derivatives in which one ring of the tetrahydrocarbazolone system was opened were also prepared. Compounds were tested in radioligand binding assays on human cloned alpha1A-AR, alpha1B-AR, and alpha1D-AR subtypes stably expressed in HEK293 cells. They showed moderate to good affinities, although their selectivity among the receptor subtypes hardly reached one order of magnitude.

Following a program searching for dual 5-HT reuptake inhibitors and alpha(2)-adrenoceptor antagonists started at Johnson & Johnson Pharmaceutical Research & Development, we now report on the synthesis of a series of 7-amino-3a,4-dihydro-3H-[1]benzopyrano[4,3-c]isoxazole derivatives, some of which proved to be the most potent alpha(2)-adrenoceptor blockers within this chemical class of tricyclic isoxazolines, while keeping potent 5-HT reuptake inhibiting activity.

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.

A series of new alpha1-adrenoreceptor antagonists (5-18) was prepared by introducing various substituents (Topliss approach) into the ortho, meta, and para positions of the benzyloxy function of the phendioxan open analogue 4 ("openphendioxan"). All the compounds synthesized were potent antagonists and generally displayed, similarly to 4, the highest affinity values at alpha1D- with respect to alpha1A- and alpha1B-AR subtypes and 5-HT1A subtype. By sulforhodamine B (SRB) assay on human PC-3 prostate cancer cells, the new compounds showed antitumor activity (estimated on the basis of three parameters GI50, TGI, LC50), at low micromolar concentration, with 7 ("clopenphendioxan") exhibiting the highest efficacy. Moreover, this study highlighted for the first time alpha1D- and alpha1B-AR expression in PC3 cells and also demonstrated the involvement of these subtypes in the modulation of apoptosis and cell proliferation. A significant reduction of alpha1D- and alpha1B-AR expression in PC3 cells was associated with the apoptosis induced by 7. This depletion was completely reversed by norepinephrine.

The synthesis and biological evaluation of a new series of bioisosteric phentolamine analogs are described. Replacement of the carbon next to the imidazoline ring of phentolamine with a nitrogen atom provides compounds (2, 3) that are about 1.6 times and 4.1 times more potent functionally than phentolamine on rat alpha1-adrenergic receptors, respectively. In receptor binding assays, the affinities of phentolamine and its bioisosteric analogs were determined on the human embryonic kidney (HEK) and Chinese Hamster ovary (CHO) cell lines expressing the human alpha1- and alpha2-AR subtypes, respectively. Analogs 2 and 3, both, displayed higher binding affinities at the alpha2- versus the alpha1-ARs, affinities being the least at the alpha1B-AR. Binding affinities of the methoxy ether analog 2 were greater than those of the phenolic analog 3 at all six alpha-AR subtypes. One of the nitrogen atoms in the imidazoline ring of phentolamine was replaced with an oxygen atom to give compounds 4 and 5, resulting in a 2-substituted oxazoline ring. The low functional antagonist activity on rat aorta, and binding potencies of these two compounds on human alpha1A- and alpha2A-AR subtypes indicate that a basic functional group is important for optimum binding to the alpha1- and alpha2A-adrenergic receptors.

Phenyl-piperazines were designed and synthesized based on pharmacophore for uro-selective alpha(1)-adrenoceptor antagonists and 3D chemical database searching. Within this series, three compounds, 2, 3, and 13, showed similar or better alpha(1)-AR antagonistic activity compared with prazosin. The 3D-QSAR study of these compounds may provide useful information for the development of novel aryl-piperazines as uro-selective alpha(1)-adrenoceptor antagonists, which can be used for the treatment of BPH with fewer side effects.

New oxypropanol alpha- and beta-adrenoceptor blocking agents, analogs of labetalol, were synthesised and studied in vitro in left atria and aorta for alpha and beta activity.

To combine in the same molecule alpha(1)-adrenoreceptor blocking and antioxidant properties, compounds 2-5 were designed and synthesized. All compounds were effective alpha(1)-adrenoreceptor antagonists and were tested in both functional and binding assays. In addition, compounds 2 and 5 also displayed significant capacity to inhibit intracellular oxidative stress, whereas 3-5 exerted potent antiproliferative activity in lymph node carcinoma of prostate cells.

The alpha1-adrenoreceptor antagonist doxazosin induces apoptosis in malignant cells with moderate potency via an alpha1-adrenoreceptor-independent mechanism. Here, we demonstrate that the ability of doxazosin to induce apoptosis in PC-3 prostate cancer cells was, in part, attributable to the inhibition of protein kinase B (PKB)/Akt activation. The separation of the effect of doxazosin on apoptosis from its original pharmacological activity provides molecular underpinnings to develop novel antitumor agents. Replacement of the (2,3-dihydro-benzo[1,4]dioxane)-carbonyl moiety of doxazosin with aryl-sulfonyl functions dramatically improves the potency in facilitating Akt deactivation and inducing apoptosis. The optimal compounds, 33 and 44, were effective in apoptosis induction at low micromolar concentrations irrespective of androgen dependency and p53 functional status. Both agents were active in suppressing the growth of a panel of 60 cancer-cell lines with IC50 values of 2.2 and 1.5 microM, respectively. Together, these in vitro efficacy data suggest the translational potential of these agents in prostate cancer treatment.

In the present study, more than 75 compounds structurally related to BMY 7378 have been designed and synthesized. Structural variations of each part of the reference molecule have been introduced, obtaining highly selective ligands for the alpha(1d) adrenergic receptor. The molecular determinants for selectivity at this receptor are essentially held by the phenyl substituent in the phenylpiperazine moiety. The integration of an extensive SAR analysis with docking simulations using the rhodopsin-based models of the three alpha(1)-AR subtypes and of the 5-HT(1A) receptor provides significant insights into the characterization of the receptor binding sites as well as into the molecular determinants of ligand selectivity at the alpha(1d)-AR and the 5-HT(1A) receptors. The results of multiple copies simultaneous search (MCSS) on the substituted phenylpiperazines together with those of manual docking of compounds BMY 7378 and 69 into the putative binding sites of the alpha(1a)-AR, alpha(1b)-AR, alpha(1d)-AR, and the 5-HT(1A) receptors suggest that the phenylpiperazine moiety would dock into a site formed by amino acids in helices 3, 4, 5, 6 and extracellular loop 2 (E2), whereas the spirocyclic ring of the ligand docks into a site formed by amino acids of helices 1, 2, 3, and 7. This docking mode is consistent with the SAR data produced in this work. Furthermore, the binding site of the imide moiety does not allow for the simultaneous involvement of the two carbonyl oxygen atoms in H-bonding interactions, consistent with the SAR data, in particular with the results obtained with the lactam derivative 128. The results of docking simulations also suggest that the second and third extracellular loops may act as selectivity filters for the substituted phenylpiperazines. The most potent and selective compounds for alpha(1d) adrenergic receptor, i.e., 69 (Rec 26D/038) and 128 (Rec 26D/073), are characterized by the presence of the 2,5-dichlorophenylpiperazine moiety.

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.

A series of 3-substituted tetrahydro-[1,8]naphthyridine containing alpha(v)beta(3) antagonists was prepared. A comparison of their in vitro IC(50) values to the electron properties of the 3-substituents revealed a good linear Hammett correlation (rho=-1.96, R(2)=0.959). Electron-withdrawing groups at the 3-position of the tetrahydro-[1,8]naphthyridine decreased potency while electron-donating groups enhanced potency.

Antagonists of the integrin receptor alpha(v)beta(3) are expected to have utility in the treatment of osteoporosis through inhibition of bone resorption. A series of potent, chain-shortened, pyrrolidinone-containing alpha(v)beta(3) receptor antagonists is described. Two sets of diasteromeric pairs of high-affinity antagonists demonstrated marked differences in log P values, which translated into differing dog pharmacokinetic properties. One member of this set was demonstrated to be effective in reducing bone resorption in rats.

In a search for structurally new alpha(1)-adrenoreceptor (alpha(1)-AR) antagonists, prazosin (1)-related compounds 2-11 were synthesized and their affinity profiles were assessed by functional experiments in isolated rat vas deferens (alpha(1A)), spleen (alpha(1B)), and aorta (alpha(1D)) and by binding assays in CHO cells expressing human cloned alpha(1)-AR subtypes. Transformation of the piperazinylquinazoline moiety of 1 into an aminomethyltetrahydroacridine system afforded compound 2, endowed with reduced affinity, in particular for the alpha(1A)-AR subtype. Then, to investigate the optimal features of the tricyclic moiety, the aliphatic ring of 2 was modified by synthesizing the lower and higher homologues 3 and 4. An analysis of the pharmacological profile, together with a molecular modeling study, indicated the tetrahydroacridine moiety as the most promising skeleton for alpha(1)-antagonism. Compounds 5-8, where the replacement of the furoyl group of 2 with a benzoyl moiety afforded the possibility to evaluate the effect of the substituent trifluoromethyl on receptor binding, resulted, except for 7, in a rather surprising selectivity toward alpha(1B)-AR, in particular vs the alpha(1A) subtype. Also the insertion of the 2,6-dimethoxyphenoxyethyl function of WB 4101 on the tetrahydroacridine skeleton of 2, and/or the replacement of the aromatic amino function with a hydroxy group, affording derivatives 9-11, resulted in alpha(1B)-AR selectivity also vs the alpha(1D) subtype. On the basis of these results, the tetrahydroacridine moiety emerged as a promising tool for the characterization of the alpha(1)-AR, owing to the receptor subtype selectivity achieved by an appropriate modification of the lateral substituents.

The synthesis of a series of novel 3-piperazinylmethyl-3a,4-dihydro-3H-[1]benzopyrano[4,3-c]isoxazoles as novel dual 5-HT reuptake inhibitors and alpha(2)-adrenoceptor antagonists is described. Their affinity at the three different human alpha(2)-adrenoceptor subtypes and the 5-HT transporter site is reported. The in vivo activity of the compounds was measured in two different assays: (1). inhibition of pCA-induced excitation, which evaluates the ability to block the central 5-HT transporter, and (2). inhibition of xylazine-induced loss of righting, which evaluates the ability to block central alpha(2)-adrenoceptors.

A recent uroselective alpha(1)-adrenoceptor antagonist, REC15/2739, has been joined with nitrooxy and furoxan NO-donor moieties to give new NO-donor alpha(1)-antagonists. All the compounds studied proved to be potent and selective ligands of human cloned alpha(1a)-receptor subtype. Derivatives 6 and 7 were able to relax the prostatic portion of rat vas deferens contracted by (-)-noradrenaline because of both their alpha(1A)-antagonist and their NO-donor properties.

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.

A new series of compounds were designed as structural analogues of the alpha(1)-AR ligand RN5 (4), characterized by a tricyclic 5H-pyrimido[5,4-b]indole-(1H,3H)2,4-dione system connected through an alkyl chain to a phenylpiperazine (PP) moiety. These compounds were synthesized and tested in binding assays on human alpha(1A)-AR, alpha(1B)-AR, and alpha(1D)-AR subtypes expressed in HEK293 cells. Several structural modifications were performed on the PP moiety, the tricyclic system, and the connecting alkyl chain. Many of the new molecules showed a preferential affinity for the alpha(1D)-AR subtype. Some compounds, including 39 and 40, displayed substantial alpha(1D)-AR selectivity with respect to alpha(1A)-AR, alpha(1B)-AR, serotonergic 5-HT(1A), 5-HT(1B), 5-HT(2A), and dopaminergic D(1) and D(2) receptors. Two conformationally rigid analogues of 4, useful for studying the architecture of the receptor/ligand complex, were also prepared and tested. A subset of the new compounds was then used to evolve a preliminary pharmacophore model for alpha(1D)-AR antagonists, based on a more generalized model we had developed for alpha(1)-AR antagonists. This new model rationalized the relationships between structural properties and biological data of the pyrimido[5,4-b]indole compounds, as well as other compounds.

Predominance in the urethra and prostate of the alpha(1A)-adrenoceptor subtype, which is believed to be the receptor mediating noradrenaline induced smooth muscle contraction in these tissues, led to the preparation of alpha(1A)-selective antagonists to be tested as uroselective compounds for the treatment of benign prostatic hyperplasia. Thus, a number of selective alpha(1A)-adrenoceptor antagonists were synthesized and assayed in vitro for potency and selectivity. Dog pharmacokinetic parameters of 12 (RO700004) and its metabolite 40 (RO1104253) were established. The relative selectivity of intravenously administered 12, 40 and standard prazosin to inhibit hypogastric nerve stimulation-induced increases in intraurethral prostatic pressure versus phenylephrine-induced increases in diastolic blood pressure in anesthetized dogs was 76, 71 and 0.6, respectively.

1,3-Dioxolane-based compounds (2-14) were synthesized, and the pharmacological profiles at alpha(1)-adrenoceptor subtypes were assessed by functional experiments in isolated rat vas deferens (alpha(1A)), spleen (alpha(1B)), and aorta (alpha(1D)). Compound 9, with a pA(2) of 7.53, 7.36, and 8.65 at alpha(1A), alpha(1B), and alpha(1D), respectively, is the most potent antagonist of the series, while compound 10 with a pA(2) of 8.37 at alpha(1D) subtype and selectivity ratios of 162 (alpha(1D)/alpha(1A)) and 324 (alpha(1D)/alpha(1B)) is the most selective. Binding assays in CHO cell membranes expressing human cloned alpha(1)-adrenoceptor subtypes confirm the pharmacological profiles derived from functional experiments, although the selectivity values are somewhat lower. Therefore, it is concluded that 1,3-dioxolane-based ligands are a new class of alpha(1)-adrenoceptor antagonists.

Our previous work on pyridazinone-arylpiperazine derivatives suggested some structural features that a compound should have to show high affinity and good selectivity for alpha(1) adrenoceptors (AR) with respect to alpha(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.

A new class of 5-heteroaryl-substituted 1-(4-fluorophenyl)-3-(4-piperidinyl)-1H-indoles as highly selective and potentially CNS-active alpha 1-adrenoceptor antagonists is described. The compounds are derived from the antipsychotic sertindole. The structure-affinity relationships of the 5-heteroaryl substituents, and the substituents on the piperidine nitrogen atom were optimized with respect to affinity for alpha 1 adrenoceptors and selectivity in respect to dopamine (D(1-4)) and serotonin (5-HT(1A-1B) and 5-HT(2A,2C)) receptors. The most selective compound obtained, 3-[4-[1-(4-fluorophenyl)-5-(1-methyl-1,2,4-triazol-3-yl)-1H-indol-3-yl]-1-piperidinyl]propionitrile (15c), has affinities of 0.99, 3.2, and 9.0 nM for the alpha(1a), alpha(1b), and alpha(1d) adrenoceptor subtypes, respectively, and a selectivity for adrenergic alpha(1a) receptors in respect to dopamine D2, D3, and D4 and serotonin 5-HT(2A) and 5-HT(2C) higher than 900, comparable to the selectivity of prazosin. In addition, the compound is more than 150-fold selective in respect to serotonin 5-HT(1A) and 5-HT(1B) receptors. A new basic pharmacophore for alpha 1-adrenoceptor antagonists based on a previously reported pharmacophore model for dopamine D2 antagonist is suggested.

N-[3-(1H-Imidazol-4-ylmethyl)phenyl]ethanesulfonamide (ABT-866, 1) is a novel alpha(1) agent having the unique profile of alpha(1A) (rabbit urethra, EC(50) = 0.60 microM) agonism with alpha(1B) (rat spleen, pA(2) = 5.4) and alpha(1D) (rat aorta, pA(2) = 6.2) antagonism. An in vivo dog model showed 1 to be more selective for the urethra over the vasculature than A-61603 (2), ST-1059 (3, the active metabolite of midodrine), and phenylpropanolamine (4).

The syntheses and biological activities of a novel series of 2,4- and 2,5-disubstituted thiophenes are reported. These analogues have shown excellent affinity and selectivity against alpha(1)-adrenoreceptor subtypes.

As a part of a program aimed at discovering compounds endowed with alpha(1)-adrenoceptor (AR) blocking properties, in this paper we describe the synthesis and biological characterization of the compounds designed to fully match a three-dimensional pharmacophore model for alpha(1)-AR antagonists previously developed by our research group. Accordingly, the structure of trazodone (1), identified during a database search performed by using the model as a 3D query, was chosen as the starting point for this study and modified following suggestions derived from a literature survey. In particular, the triazolopyridine moiety of trazodone was replaced with different heteroaromatic rings (such as imidazole, benzimidazole, and indole), and a pyridazin-3(2H)-one moiety was inserted into the scaffold of the new compounds to increase the overall length of the molecules and to allow for a complete fit into all the pharmacophore features. Our aim was also to study the influence of the position of both the chloro and the methoxy groups on the piperazine phenyl ring, as well as the effect of the lengthening or shortening of the polymethylene spacer linking the phenylpiperazine moiety to the terminal heterocyclic portion. Compounds obtained by such structural optimization share a 6-(imidazol-1-yl)-, 6-(benzimidazol-1-yl)-, or 6-(indol-1-yl)pyridazin-3(2H)-one as a common structural feature that represents an element of novelty in the SAR of arylpiperazine compounds acting toward alpha(1)-AR. Biological evaluation by radioligand receptor binding assays toward alpha(1)-AR, alpha(2)-AR, and 5-HT(1A) serotoninergic receptors indicated compounds characterized by very good alpha(1)-AR affinity and selectivity. Very interestingly, chemical features (such as the o-methoxyphenylpiperazinyl moiety and an alkyl spacer of three or four methylene units) that generally do not allow for 5-HT(1A)/alpha(1) selectivity led to compounds 2c and 6c with a 5-HT(1A)/alpha(1) ratio of 286 and 281, respectively. Finally, compounds with the best alpha(1)-AR affinity profile (2c, 5f, and 6c) were demonstrated to be alpha(1)-AR antagonists.

In the last years, alpha(1) adrenoceptors (alpha(1)-AR) have been the subject of intense research, in part because receptor-binding studies and molecular biology have opened up new aspects of understanding but also because of the potential to find new drugs possibly acting toward pathophysiological processes where alpha(1)-AR are involved, such as benign prostatic hyperplasia (BPH) or hypertension. At present, arylpiperazines represent one of the most studied classes of molecules with affinity at alpha(1)-AR. In fact, a large amount of work has been done and reported, describing synthetic procedures, biological evaluation at both alpha(1)-AR and the corresponding subtypes, and structure-activity relationships (SARs). In this paper, a review based on a literature survey aimed at focusing on the structural properties that a compound should possess to show affinity toward alpha(1)-AR is presented. Moreover, the identification and optimization of the structural features of a hit compound derived from a pharmacophore-based database search, leading to a new class of arylpiperazinylalkyl pyridazinone derivatives with alpha(1)-AR affinity is reported.

We synthesized some quinazoline-based compounds, such as FH-71 (ethyl 4-(3-(4-(2-methoxyphenyl)piperazinyl)aminoquinazolin-2-carboxylate), EW-65 (4-(3-(4-(2-methoxyphenyl)piperazinyl)propyl)aminoquinazolin-2-carboxamide) and EW-154 (2-(4-(4-(2-methoxyphenyl)piperazinyl)butyl)amino-4-cyclohexylamino-quinazolin), and then characterized their pharmacological properties in several tissues. All of these compounds produced potent inhibition of phenylephrine but not high K(+) or U46619 (11 alpha,9 alpha-epoxymethano-15S-hydroxy-prosta-5Z,13E-dienoic acid)-induced contractions in rat aorta, suggesting alpha(1)-adrenoceptor antagonist properties. With rat vasa deferentia and spleens as the functional alpha(1A)- and alpha(1B)-adrenoceptor models, respectively, FH-71 exhibited greater antagonistic potency in rat vas deferens, EW-154 in rat spleen, and EW-65 had similar effects in both tissues. The potency ratios of terazosin, FH-71, EW-65 and EW-154 against phenylephrine-induced contractions in rat vas deferens/spleen were 1, 19.04, 0.39 and 0.09, respectively. The results suggest that FH-71 is a selective alpha(1A)-adrenoceptor antagonist, whereas EW-154 exhibits more antagonistic selectivity against alpha(1B)-adrenoceptors. FH-71 also showed a greater potency than EW-65 and EW-154 against phenylephrine-induced contraction in human hyperplastic prostate. The pA(2) values were 8.34, 7.44 and 7.05, respectively. Furthermore, FH-71 and EW-65 were not cytotoxic whereas EW-154 (all in 10 microM) had a massive toxic effect (more than 80%) in human prostatic smooth muscle cells. These data show FH-71 to be a potent and selective alpha(1A)-adrenoceptor antagonist with activity in human hyperplastic prostate.

A series of beta-chloroethylamines 5--18, structurally related to the irreversible alpha(1)-adrenoceptor antagonist phenoxybenzamine [PB, N-benzyl-N-(2-chloroethyl)-N-(1-methyl-2-phenoxyethyl)amine hydrochloride, 1] and the competitive antagonist WB4101 [N-(2,3-dihydro-1,4-benzodioxin-2-ylmethyl)-N-[2-(2,6-dimethoxyphenoxy)ethyl]amine hydrochloride, 2], were synthesized and evaluated for their activity at alpha-adrenoceptors of the epididymal and the prostatic portion of young CD rat vas deferens. All compounds displayed irreversible antagonist activity. Most of them showed similar antagonism at both alpha(1)- and alpha(2)-adrenoceptors, whereas compounds 13 and 18, lacking substituents on both the phenoxy group and the oxyamino carbon chain, displayed a moderate alpha(1)-adrenoceptor selectivity (10--35 times), which was comparable to that of PB. Compounds 14 and 15, belonging to the benzyl series and bearing, respectively, a 2-ethoxyphenoxy and a 2-i-propoxyphenoxy moiety, were the most potent alpha(1)-adrenoceptor antagonists with an affinity value similar to that of PB (pIC(50) values of 7.17 and 7.06 versus 7.27). Interestingly, several compounds were able to distinguish two alpha(1)-adrenoceptor subtypes in the epididymal tissue, as revealed by the discontinuity of their inhibition curves. A mean ratio of 24:76 for these alpha(1)-adrenoceptors was determined from compounds 8--10, 12, and 15--17. Furthermore, compounds 9, 10, 12, 16a, and 16b showed higher affinity towards the minor population of receptors, whereas compounds 8, 15, and 17 preferentially inhibited the major population of alpha(1)-adrenoceptors. In addition, selected pharmacological experiments demonstrated the complementary antagonism of the two series of compounds and their different, preferential affinity for one of the two alpha(1)-adrenoceptor subtypes. In conclusion, we found beta-chloroethylamines that demonstrate a multiplicity of alpha(1)-adrenoceptors in the epididymal portion of young CD rat vas deferens and, as a consequence, they are possible useful tools for alpha(1)-adrenoceptor characterization.

WB4101 (1)-related compounds 5-10 were synthesized, and their biological profile at alpha(1)-adrenoreceptor (AR) subtypes and 5-HT(1A) serotoninergic receptors was assessed by binding assays in Chinese hamster ovary and HeLa cell membranes expressing the human cloned receptors. Moreover, their receptor selectivity was further determined in functional experiments in isolated rat prostate (alpha(1A)), vas deferens (alpha(1A)), aorta (alpha(1D)), and spleen (alpha(1B)). In functional assays, compound 5 was the most potent at alpha(1D)-ARs with a reversed selectivity profile (alpha(1D) > alpha(1A) > alpha(1B)) relative to both prototype 1 and phendioxan (2) (alpha(1A) > alpha(1D) > alpha(1B)), whereas compound 8, bearing a carbonyl moiety at position 1, was the most potent at alpha(1A)-ARs with a selectivity profile similar to that of prototypes. The least potent of the series was the trans isomer 6, suggesting that optimum alpha(1)-AR blocking activity in this series is associated with a cis relationship between the 2-side chain and the 4-phenyl ring rather than a trans relationship as previously observed for the 2-side chain and the 3-phenyl ring in 2 and related compounds. Binding affinity results were not in complete agreement with the selectivity profiles deriving from functional experiments. Although a firm explanation was not available, neutral and negative antagonism and receptor dimerization were considered as two possibilities to account for the difference between binding and functional affinities. Finally, compound 5 was selected for a modeling study in comparison with 1, mephendioxan (3), and open phendioxan (4) to achieve information on the physicochemical interactions that account for its high affinity toward alpha(1d/D)-ARs.