Molecular modeling study and synthesis of quinazolinone-arylpiperazine derivatives as α1-adrenoreceptor antagonists

Recent achievements in the synthesis of benzimidazole derivatives

Benzimidazoles are a class of heterocyclic compounds in which a benzene ring is fused to the 4 and 5 positions of an imidazole ring. Benzimidazole refers to the parent compound, while benzimidazoles are a class of heterocyclic compounds having similar ring structures, but different substituents. Benzimidazole derivatives possess a wide range of bioactivities including antimicrobial, anthelmintic, antiviral, anticancer, and antihypertensive activities. Many compounds possessing a benzimidazole skeleton have been employed as drugs in the market. The application of benzimidazoles in other fields has also been documented. The synthesis of benzimidazole derivatives has attracted much attention from chemists and numerous articles on the synthesis of this class of heterocyclic compound have been reported over the years. The condensation between 1,2-benzenediamine and aldehydes has received intensive interest, while many novel methods have been developed. In this article, we will give a comprehensive review of studies on the synthesis of benzimidazole, which date back to 2013. We have also tried to describe reaction mechanisms as much as we can. The work might be useful for chemists who work in the synthesis of heterocycles or drug chemistry.

A Comprehensive Account on Recent Progress in Pharmacological Activities of Benzimidazole Derivatives

Nowadays, nitrogenous heterocyclic molecules have attracted a great deal of interest among medicinal chemists. Among these potential heterocyclic drugs, benzimidazole scaffolds are considerably prevalent. Due to their isostructural pharmacophore of naturally occurring active biomolecules, benzimidazole derivatives have significant importance as chemotherapeutic agents in diverse clinical conditions. Researchers have synthesized plenty of benzimidazole derivatives in the last decades, amidst a large share of these compounds exerted excellent bioactivity against many ailments with outstanding bioavailability, safety, and stability profiles. In this comprehensive review, we have summarized the bioactivity of the benzimidazole derivatives reported in recent literature (2012-2021) with their available structure-activity relationship. Compounds bearing benzimidazole nucleus possess broad-spectrum pharmacological properties ranging from common antibacterial effects to the world's most virulent diseases. Several promising therapeutic candidates are undergoing human trials, and some of these are going to be approved for clinical use. However, notable challenges, such as drug resistance, costly and tedious synthetic methods, little structural information of receptors, lack of advanced software, and so on, are still viable to be overcome for further research.

Synthetic and medicinal chemistry of phthalazines: Recent developments, opportunities and challenges

Fused diaza-heterocycles constitute the core structure of numerous bioactive natural products and effective therapeutic drugs. Among them, phthalazines have been recognized as remarkable structural leads in medicinal chemistry due to their wide application in pharmaceutical and agrochemical industries. Accessing such challenging pharmaceutical agents/drug candidates with high chemical complexity through synthetically efficient approaches remains an attractive goal in the contemporary medicinal chemistry and drug discovery arena. In this review, we focus on the recent developments in the synthetic routes towards the generation of phthalazine-based active pharmaceutical ingredients and their biological potential against various targets. The general reaction scope of these innovative and easily accessible strategies was emphasized focusing on the functional group tolerance, substrate and coupling partner compatibility/limitation, the choice of catalyst, and product diversification. These processes were also accompanied by the mechanistic insights where deemed appropriate to demonstrate meaningful information. Moreover, the rapid examination of the structure-activity relationship analyses around the phthalazine core enabled by the pharmacophore replacement/integration revealed the generation of robust, efficient, and more selective compounds with pronounced biological effects. A large variety of in silico methods and ADME profiling tools were also employed to provide a global appraisal of the pharmacokinetics profile of diaza-heterocycles. Thus, the discovery of new structural leads offers the promise of improving treatments for various tropical diseases such as tuberculosis, leishmaniasis, malaria, Chagas disease, among many others including various cancers, atherosclerosis, HIV, inflammatory, and cardiovascular diseases. We hope this review would serve as an informative collection of structurally diverse molecules enabling the generation of mature, high-quality, and innovative routes to support the drug discovery endeavors.

Elucidation of Vasodilation Response and Structure Activity Relationships of N²,N⁴-Disubstituted Quinazoline 2,4-Diamines in a Rat Pulmonary Artery Model

Pulmonary arterial hypertension (PAH) is a rare and progressive disease arising from various etiologies and pathogenesis. PAH decreases life expectancy due to pulmonary vascular remodeling, elevation of mean pulmonary arterial pressure, and ultimately progresses to heart failure. While clinical treatments are available to reduce the associated symptoms, a complete cure has yet to be found. Phosphodiesterase-5 (PDE-5) inhibition has been identified as a possible intervention point in PAH treatment. The functional vasodilation response to N²,N⁴-diamino quinazoline analogues with differing PDE-5 inhibitory activities and varying physicochemical properties were assessed in both endothelium-intact and denuded rat pulmonary arteries to gain greater insight into their mode of action. All analogues produced vasorelaxant effects with EC50s ranging from 0.58 ± 0.22 µM to ˃30 µM. It was observed that vasodilation response in intact vessels was highly correlated with that of denuded vessels. The ~10% drop in activity is consistent with a loss of the nitric oxide mediated cyclic guanosine monophosphate (NO/cGMP) pathway in the latter case. A moderate correlation between the vasodilation response and PDE-5 inhibitory activity in the intact vessels was observed. Experimental protocol using the alpha-adrenergic (α₁) receptor agonist, phenylephrine (PE), was undertaken to assess whether quinazoline derivatives showed competitive behavior similar to the α₁ receptor blocker, prazosin, itself a quinazoline derivative, or to the PDE-5 inhibitor, sildenafil. Competitive experiments with the α₁-adrenergic receptor agonist point to quinazoline derivatives under investigation here act via PDE-5 inhibition and not the former. The pre-incubation of pulmonary arterial rings with quinazoline test compounds (10 μM) reduced the contractile response to PE around 40–60%. The most promising compound (9) possessed ~32 folds higher selectivity in terms of vasodilation to its mammalian A549 cell cytotoxicity. This study provides experi0 0mental basis for PDE-5 inhibition as the mode of action for vasodilation by N²,N⁴-diamino quinazoline analogues along with their safety studies that may be beneficial in the treatment of various cardiovascular pathologies.

Novel naftopidil derivatives containing methyl phenylacetate and their blocking effects on α1D/1A-adrenoreceptor subtypes

α₁-Adrenoceptor (α₁-AR) antagonists are considered to be the most effective monotherapy agents for lower urinary tract symptoms associated with benign prostatic hyperplasia (LUTS/BPH). In this study, we synthesized compounds 2-17, which are novel piperazine derivatives that contain methyl phenylacetate. We then evaluated the vasodilatory activities of these compounds. Among them, we found that compounds 2, 7, 12, which contain 2-OCH₃, 2-CH₃ or 2, 5-CH₃, respectively, exhibited potent α₁-blocking activity similar to protype drug naftopidil (1). The antagonistic effects of 2, 7, and 12 on the (-)-noradrenaline-induced contractile response of isolated rat prostatic vas deferens (α_1A), spleen (α_1B) and thoracic aorta (α_1D) were further characterized to assess the sub receptor selectivity. Compared with naftopidil (1) and terazosin, compound 12 showed the most desirable α_1D/1A subtype selectivity, especially improved α_1A subtype selectivity, and the ratios pA₂ (α_1D)/pA₂ (α_1B) and pA₂ (α_1A)/pA₂ (α_1B) were 17.0- and 19.5-fold, respectively, indicating less cardiovascular side effects when used to treat LUTS/BPH. Finally, we investigated the chiral pharmacology of 12. We found, however, that the activity of enantiomers (R)-12 and (S)-12 are not significantly different from that of rac-12.

New organometallic imines of rhenium(i) as potential ligands of GSK-3β: synthesis, characterization and biological studies

Substituted amino-piperazine derivatives were synthesized and used as precursors for the preparation of a series of new organometallic Re(i) imine complexes with the general formula [(η⁵-C₅H₄CH[double bond, length as m-dash]N-(CH₂)₅-Pz-R)Re(CO)₃] (Pz-R: -alkyl or aryl piperazine). The piperazine-based ligands were designed to be potential inhibitors of GSK-3β kinase. All the ligands and complexes were fully characterized and evaluated against the HT-29 and PT-45 cancer cell lines, in which GSK-3β plays a crucial role. In this context, we carried out biological evaluation using the MTT colorimetric assay. In terms of structure activity relationship, our findings indicated improved biological activity when aromaticity increased in the organic ligands (3d). In addition, the presence of the rhenium fragment in the imines (5a-d) leads to better activity with IC₅₀ values in the range of 25-100 μM. In addition, our experimental studies were complemented by computational studies, where the volume and electrostatic surface of the organic ligands and organometallic compounds as well as their binding to the kinase protein are calculated.

Design, synthesis and biological evaluation of some novel quinazolinone derivatives as potent apoptotic inducers

Aim: Novel quinazolinone and triazinoquinazolinone derivatives were designed and synthesized as apoptotic inducers. Methodology/results: Most of the synthesized compounds showed excellent antiproliferative activity against MCF-7 and HCT-116 cell lines, respectively. Compounds 7a, 8a, 8d, 14a and 14d were superior to doxorubicin as activators of caspases 3, 8 and 9 in HCT-116 cell line. The most potent caspase inducers, 8d and 14a showed cell cycle arrest mainly in G1 and S phase, respectively and increased the levels of p53, Bax and the Bax/Bcl-2 ratio compared with doxorubicin in HCT-116 cells with excellent selectivity against CCD-18Co human colon normal cell line. Conclusion: The synthesized compounds can be considered as potent apoptotic inducers interfering with extrinsic and intrinsic apoptotic pathways.

Palladium-catalyzed selective synthesis of 3,4-dihydroquinazolines from electron-rich arylamines, electron-poor arylamines and glyoxalates

Palladium-catalyzed selective synthesis of various 3,4-dihydroquinazolines from electron-rich arylamines, electron-poor arylamines and glyoxalates was developed.

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 α_1D subtype. Tissue functional assay in vitro showed that compound 2 exerted strong antagonistic activity on α_1B-AR (pA₂ 7.13) with a poor selectivity for α_1A and α_1D subtypes. Compound 1 exhibited enhanced antagonistic effect on α_1D subtype (pA₂ 7.06) and excellent selectivity for α_1D over α_1B (α_1D/α_1B 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 α_1D-selective antagonists.

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.

Design, synthesis and biological evaluation of novel 7-mercaptocoumarin derivatives as α(1)-adrenoceptor antagonists

Study on the pharmacophore model of α(1)-adrenoceptor (α(1)-AR) antagonists led to design a series of novel 7-mercaptocoumarin derivatives as α(1)-AR antagonists. All designed compounds have been synthesized and biologically evaluated. The results showed that most of them exhibited strong antagonistic activity. Especially compound 6 showed excellent activity, which was better than that of the reference compound prazosin. Structure-activity relationship studies revealed that small hydrophobic group at the terminal heterocyclic ring and ortho substituents on the phenyl ring of phenylpiperazine moiety were the essential structural factors for α(1)-AR antagonistic activity. The pharmacophore modeling studies further clarified their structural contributions to antagonistic activity and also demonstrated that 7-mercaptocoumarin moiety could be a useful scaffold for design of α(1)-AR antagonists.