New pyrimido[5,4-b]indoles and [1]benzothieno[3,2-d]pyrimidines: High affinity ligands for the α1-adrenoceptor subtypes

Design, synthesis and biological evaluation of dual Topo II/HDAC inhibitors bearing pyrimido[5,4-b]indole and pyrazolo[3,4-d]pyrimidine motifs

Both topoisomerase II (Topo II) and histone deacetylase (HDAC) are important therapeutic targets for cancer. In this study, two series of novel compounds containing pyrimido[5,4-b]indole and pyrazolo[3,4-d]pyrimidine motifs were designed and synthesized as dual Topo II/HDAC inhibitors. MTT assay indicated that all the compounds displayed potential antiproliferative activity against three cancer cell lines (MGC-803, MCF-7 and U937) and low cytotoxicity on normal cell line (3T3). In the enzyme activity inhibition experiments, compounds 7d and 8d exhibited excellent dual inhibitory activities against Topo II and HDAC. Cleavage reaction assay showed that 7d was a Topo II poison, which was consistent with the docking results. Further experimental results revealed that compounds 7d and 8d could promote apoptosis and significantly inhibit the migration in MCF-7 cells. Molecular docking showed that compounds 7d and 8d bind Topo II and HDAC at the active sites. Molecular dynamics simulation showed that 7d can stably bind to Topo II and HDAC.

Synthesis, in vitro and in silico studies of HO-1 inducers and lung antifibrotic agents

Aim: Dimethyl fumarate (DMF) analogs were synthesized to obtain inducers of HO-1 and antifibrotic agents. Methods: HO-1 expression levels were measured on lung fibroblasts (MRC5). NMR and docking studies were performed. Heme oxygenase activity, gene levels and protein expression have been measured for the most active compound 1a. Collagen production by fibroblast after exposure to TGF-β was measured. Results: Compound 1a showed to be a strong HO-1 inducer. Its activity seems to be mediated by activation of nuclear factor erythroid 2 related factor 2 (Nrf2). TGF-β-induced collagen production was significantly decreased on MRC5, pretreated with DMF or 1a. DMF and 1a have a high potential for treatment of lung fibrotic injuries.

Synthesis, in vitro and in vivo characterization of new benzoxazole and benzothiazole-based sigma receptor ligands

A new set of 5-chlorobenzoxazole- and 5-chlorobenzothiazole-based derivatives containing the azepane ring as a basic moiety was designed, synthesized and evaluated through binding assays to measure their affinity and selectivity towards σ₁ and σ₂ receptors. Compounds 19, 22 and 24, with a four units spacer between the bicyclic scaffold and the azepane ring, showed nanomolar affinity towards both receptor subtype and the best K_i values (K_i σ₁ = 1.27, 2.30, and 0.78 and K_i σ₂ = 7.9, 3.8, and 7.61 nM, respectively). Evaluation of cytotoxic and apoptotic effects in MCF-7 human cancer cells was useful to assess σ₂ receptor activity, while an in vivo mice model of inflammatory pain allowed to analyze σ₁ receptor pharmacological properties. In vitro and in vivo results suggested that compound 19 is a σ₁/σ₂ agonist, compound 24 a σ₁ antagonist/σ₂ agonist, whereas compound 22 might act as σ₁ antagonist/σ₂ partial agonist. Due to their pharmacological profile, a potential therapeutic application in cancer of aforesaid novel σ₁/σ₂ receptor ligands, especially 22 and 24, is proposed.

Facile synthetic approach towards vasorelaxant active 4-hydroxyquinazoline-4-carboxamides

A Facile synthetic approach is reported towards 4-hydroxyquinazoline-4-carboxamides 13a–i through ring expansion of 2,3-dioxoindoline-1-carboxamides 10a–c during secondary amine 11a–d nucleophilic reaction. Single crystal X-ray studies of 10c and 13d support the structures. Some of the synthesized quinazolinecarboxamides 13 show promising vasorelaxant properties with potency higher than that of Doxazosin through the pre-contracted (norepinephrine hydrochloride) rat aorta standard bioassay. Good molecular models (2D-QSAR, pharmacophore) describe the biological observations.

A set of vasorelaxant active 4-hydroxyquinazoline-4-carboxamides was obtained in a novel synthetic approach via secondary amine nucleophilic reaction with 2,3-dioxoindoline-1-carboxamides.

New N- and O-arylpiperazinylalkyl pyrimidines and 2-methylquinazolines derivatives as 5-HT7 and 5-HT1A receptor ligands: Synthesis, structure-activity relationships, and molecular modeling studies

Based on our earlier studies of structure activity relationships on 4-substituted piperazine derivatives, in this work we synthesized a novel set of long-chain arylpiperazines with the purpose of elucidating if some structural modifications in the terminal fragment could affect the binding affinity for the 5-HT₇ and 5-HT_1A receptors. In this new series, the quinazolinone system of the previous derivatives was replaced by a 6-phenylpyrimidine or a 2-methylquinazoline, which were used as versatile building blocks for the preparation of new compounds. A 4-arylpiperazine moiety through a five methylene chain was anchored at the nitrogen or oxygen atom of the heterocyclic scaffolds. The substituents borne by the piperazine nucleus were phenyl, phenylmethyl, 3- or 4-chlorophenyl, and 2-ethoxyphenyl. Binding tests, performed on human cloned 5-HT₇ and 5-HT_1A receptors, showed that, among the newly synthesized derivatives, 4-[5-[4-(2-ethoxyphenyl)-1-piperazinyl]pentoxy]-6-phenyl-pyrimidine (13) and 3-[5-[4-(2-ethoxyphenyl)-1-piperazinyl]pentyl]-2-methyl-4(3H)-quinazolinone (20) displayed the best affinity values, K_i=23.5 and 8.42nM for 5-HT₇ and 6.96 and 2.99nM for 5-HT_1A receptors, respectively. Moreover, the functional properties for both compounds were further evaluated using the cAMP assay. Finally, a molecular modeling study has been performed for 5-HT₇ and 5-HT_1A receptor homology models to investigate the binding mode of N- and O-alkylated pyrimidinones/pyrimidines 4-13, 2-methylquinazolinones/quinazolines 17-22, and previously reported 2- and 3-substituted quinazolinones 23-30.

Arylsulfonamide derivatives of (aryloxy)ethyl pyrrolidines and piperidines as α1-adrenergic receptor antagonist with uro-selective activity

A series of arylsulfonamide derivatives of (aryloxy)ethyl pyrrolidines and piperidines was synthesized to develop new α₁-adrenoceptor antagonists with uroselective profile. Biological evaluation for α₁- and α₂-adrenorecepor showed that tested compounds 13-37 displayed high-to-moderate affinity for the α₁-adrenoceptor (K_i=34-348nM) and moderate selectivity over α₂-receptor subtype. Compounds with highest affinity and selectivity for α₁-adrenoceptor were evaluated in vitro for their intrinsic activity toward α_1A- and α_1B-adrenoceptor subtypes. All compounds behaved as antagonists at both α₁-adrenoceptor subtypes, displaying 2- to 6-fold functional preference to α_1A-subtype. Among them, N-{1-[2-(2-methoxyphenoxy)ethyl]piperidin-4-yl}isoquinoline-4-sulfonamide (25) and 3-chloro-2-fluoro-N-{[1-(2-(2-isopropoxyphenoxy)ethyl)piperidin-4-yl]methyl}benzene sulfonamide (34) displayed the highest preference to α_1A-adrenoceptor. Finally, compounds 25 and 34 (2-5mg/kg, iv), in contrast to tamsulosin (1-2mg/kg, iv), did not significantly decrease systolic and diastolic blood pressure in normotensive anesthetized rats to determine their influence on blood pressure.

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.

An α1-adrenergic receptor ligand repurposed as a potent antiproliferative agent for head and neck squamous cell carcinoma

In this study we report the anticancer properties of RN5-Me, an α₁-adrenergic receptor ligand.

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).

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.