1,4-Dihydropyridine Scaffold in Medicinal Chemistry, The Story So Far And Perspectives (Part 2): Action in Other Targets and Antitargets

Synthesis of fused 1,4-dihydropyridines as potential calcium channel blockers

Objective

The aim of this study was to synthesize ten 1,4-dihydropyridine (DHP) derivatives in which substituted cyclohexane rings were fused to the DHP ring and to determine how different ester groups and the benzoyl substituent introduced in 4-phenyl ring affected their calcium channel blocking activity.

Methods

A microwave-assisted one-pot method was applied for the synthesis of compound 1–5 according to a modified Hantzsch reaction. The benzoyl moiety was introduced in the 4-phenyl ring of these dihydropyridines by refluxing with benzoyl chloride in acetone in the presence of anhydrous potassium carbonate. Synthesized products were characterized by elemental analysis, IR, 1H-NMR and 13C-NMR spectroscopy. The inhibitory actions of compounds 1–10 on calcium channel blocking activity were tested on isolated rat aorta preparations.

Results

The obtained pharmacological results showed that although all compounds are potent relaxing agents on isolated rat aorta smooth muscle, introduction of a benzoyloxy substitiuent on the phenyl ring (compound 6–10) decreased the relaxant effect of these compunds.

Conclusion

The reported 1,4-DHP derivatives have calcium channel blocking activity on rat aorta smooth muscle.

Hibiscus Sabdariffa L. Flowers and Olea Europea L. Leaves Extract-Based Formulation for Hypertension Care: In Vitro Efficacy and Toxicological Profile

Olea europaea L. leaves extract (Oe) and Hybiscus sabdariffa L. flowers extract (Hs) have calcium antagonistic properties. Aim of this work was to study the cardiovascular effects of Pres Phytum(®), a nutraceutical formulation containing a mixture of the two extracts and the excipients, and investigate its possible off-target effects, using in vitro biological assays on guinea pig isolated organs. Cardiovascular effects were assessed using guinea pig atria and aorta. The effects of Pres Phytum on spontaneous gastrointestinal, urinary, and respiratory tracts smooth muscle contractility were evaluated. Pres Phytum exerted a vasorelaxant effect (IC50 = 2.38 mg/mL) and a negative chronotropic effect (IC50 = 1.04 mg/mL) at concentrations lower than those producing smooth muscle spontaneous contractility alterations in the other organs. Compared to Pres Phytum, the mixture did not exert negative inotropic activity, while it maintained a negative chronotropic efficacy (IC50 = 1.04 mg/mL). These experimental data suggest a possible nutraceutical use of this food supplement for the management of preclinical hypertension.

Ultrasonic synthesis, characterization, and antibacterial evaluation of novel heterocycles containing hexahydroquinoline and pyrrole moieties

Condensation reaction of dimedone with 2-amino-1-methyl-4,5-diphenyl-1

Facile one-pot four-component synthesis of 3,4-dihydro-2-pyridone derivatives: novel urease inhibitor scaffold

In the current study, a series of 3,4-dihydro-2-pyridone derivatives were synthesized in a one-pot fourcomponent reaction of Meldrum's acid, benzaldehyde derivatives, methyl acetoacetate, and ammonium acetate. SiO2-Pr-SO3H was used as an efficient catalyst for the synthesis of the target compounds under solvent-free conditions. The most probable mechanism for this reaction has been discussed. The advantages of this methodology are high product yields, being environmentally benign, short reaction times, and easy handling. Eight 2-pyridinone derivatives were evaluated for their inhibitory activities against Jack bean urease. Molecular docking study of the synthesized compounds was also evaluated. All compounds showed good activities against urease and among them, 4-(4-nitrophenyl)-5-methoxycarbonyl-6-methyl-3,4-dihydropyridone (5a) showed the most potent activity (IC₅₀ = 29.12 µM), more potent than hydroxyurea as the reference drug (IC₅₀ = 100.0 µM). Also, the results from docking studies were in good agreement with those obtained with in vitro assay. According to the docking studies methionine (Met) 637 and nitro phenyl ring cause n-π interaction between lone pair of sulfur atom and π aromatic ring. Moreover, hydrophobic interactions existed between compound 5a and alanine (ALA) 636, ALA 440, and isoleucine 411. The results indicated that the inhibitory activities increased with the increase of electron withdrawing ability of the groups despite a less important role of lipophilicity in increasing the inhibitory activity.

The Hantzsch reaction in polymer chemistry: synthesis and tentative application

The recent utilization of the tetra-component Hantzsch reaction in polymer chemistry has been summarized.

Theoretical and experimental study of the ground and excited states of 1,4-dihydropyridine based hexahydroquinoline derivatives achieved by microwave irradiation

The photophysical study indicates ICT state for 1,4-dihydropyridine based hexahydroquinoline derivatives.

Chemoenzymatic synthesis of optically active phenolic 3,4-dihydropyridin-2-ones: a way to access enantioenriched 1,4-dihydropyridine and benzodiazepine derivatives

Kinetic resolution of 3,4-DHP-2-ones with Candida rugose lipase (CRL) has been possible due to the presence of a reactive phenolic ester in a remote position.

1,4-Dihydropyridine Derivatives: Dihydronicotinamide Analogues-Model Compounds Targeting Oxidative Stress

Many 1,4-dihydropyridines (DHPs) possess redox properties. In this review DHPs are surveyed as protectors against oxidative stress (OS) and related disorders, considering the DHPs as specific group of potential antioxidants with bioprotective capacities. They have several peculiarities related to antioxidant activity (AOA). Several commercially available calcium antagonist, 1,4-DHP drugs, their metabolites, and calcium agonists were shown to express AOA. Synthesis, hydrogen donor properties, AOA, and methods and approaches used to reveal biological activities of various groups of 1,4-DHPs are presented. Examples of DHPs antioxidant activities and protective effects of DHPs against OS induced damage in low density lipoproteins (LDL), mitochondria, microsomes, isolated cells, and cell cultures are highlighted. Comparison of the AOA of different DHPs and other antioxidants is also given. According to the data presented, the DHPs might be considered as bellwether among synthetic compounds targeting OS and potential pharmacological model compounds targeting oxidative stress important for medicinal chemistry.

Acid-promoted rapid solvent-free access to substituted 1,4-dihydropyridines from β-ketothioamides

1,4-Dihydropyridines were synthesized via a tandem reaction of β-ketothioamides with aldehydes and β-enaminonitriles by AcOH as a promoter within 5 min.

Visible light triggered, catalyst free approach for the synthesis of thiazoles and imidazo[2,1-b]thiazoles in EtOH : H2O green medium

A catalyst free visible light assisted synthesis of thiazoles and imidazo[2,1-b]thiazoles in EtOH : H₂O green medium.

Direct Aminolysis of Ethoxycarbonylmethyl 1,4-Dihydropyridine-3-carboxylates

The ethoxycarbonylmethyl esters of 1,4-dihydropyridines were directly converted into carbamoylmethyl esters in the presence of 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) in good to excellent yields under mild conditions. The use of TBD is crucial for the successful aminolysis of ethoxycarbonylmethyl ester of 1,4-dihydropyridines with secondary amines as without it the reaction does not proceed at all. The aminolysis reaction proceeded regioselectively, as the alkyl ester conjugated with the 1,4-dihydropyridine cycle was not involved in the reaction. Screening of other N-containing bases, such as triethylamine (TEA), pyridine, 4-(N,N-dimethylamino)pyridine (DMAP), 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), 1,5-diazabicyclo[4.3.0]non-5-ene (DBN), imidazole, tetramethyl guanidine (TMG) and 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene (MTBD) as catalysts revealed no activity in the studied reaction.

Cardiac and Vascular Synergic Protective Effect of Olea europea L. Leaves and Hibiscus sabdariffa L. Flower Extracts

This study was aimed at investigating the cardiovascular effects of an Olea europea L. leaf extract (OEE), of a Hibiscus sabdariffa L. flower extract (HSE), and of their 13 : 2 w/w mixture in order to assess their cardiac and vascular activity. Both extracts were fully characterized in their bioactive compounds by HPLC-MS/MS analysis. The study was performed using primary vascular endothelial cells (HUVECs) to investigate the antioxidant and cytoprotective effect of the extracts and their mixture and isolated guinea-pig left and right atria and aorta to evaluate the inotropic and chronotropic activities and vasorelaxant properties. In cultured HUVECs, OEE and HSE reduced intracellular reactive oxygen species formation and improved cell viability, following oxidative stress in dose-dependent manner. OEE and HSE exerted negative inotropic and vasorelaxant effects without any chronotropic property. Interestingly, the mixture exerted higher cytoprotective effects and antioxidant activities. Moreover, the mixture exerted an inotropic effect similar to each single extract, while it revealed an intrinsic negative chronotropic activity different from the single extract; its relaxant activity was higher than that of each single extract. In conclusion OEE and HSE mixture has a good potential for pharmaceutical and nutraceutical application, thanks to the synergistic effects of the single phytochemicals.

Regioselective three-component reactions of enaminones, 2-aminopyridines and enals for the synthesis of 1,2-dihydropyridines

A novel regioselective, metal-free and broadly applicable three-component approach for the synthesis of 1,2-dihydropyridines has been established.

Construction of 3,5-dinitrated 1,4-dihydropyridines modifiable at 1,4-positions by a reaction of β-formyl-β-nitroenamines with aldehydes

A novel and efficient method for the synthesis of 4-substituted 3,5-dinitro-1,4-dihydropyridines by a reaction of β-formyl-β-nitroenamines with aldehydes was developed.

Campisi L, De Crescentini L, Favi G, Mantellini F. Synthesis of novel symmetrical 2-oxo-spiro[indole-3,4′-pyridines] by a reaction of oxindoles with 1,2-diaza-1,3-dienes

Synthesis of symmetrical 2-oxo-spiro[indole-3,4′-pyridines]: a novel example of spirocyclic oxindoles bearing a quaternary centre at the 3-position.

Castanea sativa Mill. extract contracts gallbladder and relaxes sphincter of Oddi in guinea pig: a natural approach to biliary tract motility disorders

Impaired gallbladder motility is a contributing factor to gallstone formation. Since many drugs delaying intestinal motility inhibit gallbladder emptying, the aim of the present study was to evaluate the effect on gallbladder and sphincter of Oddi motility of a Natural Chestnut Wood Extract (NEC) that reduces intestinal motility. In order to evaluate the effect of the extract in normal- and high-risk gallstone conditions, the investigation was performed using tissues from animals fed normal and lithogenic diet. Fifty guinea pigs were administered either control or lithogenic diet. The spontaneous motility of the gallbladder and sphincter of Oddi were recorded on isolated gallbladder tissues; thereafter, the effect of NEC on motility was tested and compared with carbachol (CCh), potassium chloride (KCl), noradrenaline (NA), and A71623. Compared to controls, the lithogenic diet induced an irregular and disordered motor pattern in both the gallbladder and sphincter of Oddi. NEC increased gallbladder and decreased sphincter of Oddi spontaneous motility independently of cholinergic, adrenergic, and CCK-1 receptor-mediated pathways both in controls and in lithogenic diet-fed animals, although the effect was lower in the latter group. The effect was reversible and mediated by calcium channels. The natural extract of chestnut increasing gallbladder contraction and inducing the relaxation of the sphincter of Oddi can be of benefit in pathological conditions associated with increased transit time at risk of gallstones.

Pharmacoperones and the calcium sensing receptor: exogenous and endogenous regulators

Calcium sensing receptor (CaSR) mutations or altered expression cause disorders of calcium handling. Recent studies suggest that reduced targeting to the plasma membrane is a feature common to many CaSR loss-of-function mutations. Allosteric agonists (calcimimetics) can rescue signaling of a subset of CaSR mutants. This review evaluates our current understanding of the subcellular site(s) for allosteric modulator rescue of CaSR mutants. Studies to date make a strong case for calcimimetic potentiation of signaling not only at plasma membrane-localized CaSR, but at the endoplasmic reticulum, acting as pharmacoperones to assist in navigation of multiple quality control checkpoints. The possible role of endogenous pharmacoperones, calcium and glutathione, in folding and stabilization of the CaSR extracellular and transmembrane domains are considered. Finally, the possibility that dihydropyridines act as unintended pharmacoperones of CaSR is proposed. While our understanding of pharmacoperone rescue of CaSR requires refinement, promising results to date argue that this may be a fruitful avenue for drug discovery.

Ligand based approach to L-type calcium channel by imidazo[2,1-b]thiazole-1,4-dihydropyridines: from heart activity to brain affinity

The synthesis, characterization, and functional in vitro assay in cardiac and smooth muscle (vascular and nonvascular) of a series of 4-imidazo[2,1-b]thiazole-1,4-dihydropyridines are reported. To define the calcium blocker nature of the imidazo[2,1-b]thiazole-1,4-DHPs and their selectivity on Cav1.2 and Cav1.3 isoforms, we performed binding studies on guinea pig atrial and ventricular membranes on intact cells expressing the cloned Cav1.2a subunit and on rat brain cortex. To get major insights into the reasons for the affinity for Cav1.2 and/or Cav1.3, molecular modeling studies were also undertaken. Some physicochemical and pharmacokinetic properties of selected compounds were calculated and compared. All the biological data collected and reported herein allowed us to rationalize the structure-activity relationship of the 4-imidazo[2,1-b]thiazole-1,4-DHPs and to identify which of these enhanced the activity at the central level.