Design, Synthesis, and Biological Evaluation of AT1 Angiotensin II Receptor Antagonists Based on the Pyrazolo[3,4-b]pyridine and Related Heteroaromatic Bicyclic Systems

Rh(III)-catalyzed [4 + 1] annulation of 1-arylindazolones with alkynyl cyclobutanols: access to indazolo[1,2-a]indazolones

A convenient and efficient synthesis of structurally diverse indazolo[1,2-a]indazolones via a Rh(III)-catalyzed [4 + 1] annulation of 1-arylindazolones with alkynyl cyclobutanols has been achieved by combining C-H and C-C bond cleavage. This cascade reaction features readily available starting materials, good functional group tolerance, broad substrate scope, and excellent atom-economy.

Emerging trends in the sustainable synthesis of N-N bond bearing organic scaffolds

N-N bond bearing organic frameworks such as azos, hydrazines, indazoles, triazoles and their structural moieties have piqued the interest of organic chemists due to the intrinsic nitrogen electronegativity. Recent methodologies with atom efficacy and a greener approach have overcome the synthetic obstacles of N-N bond construction from N-H. As a result, a wide range of amine oxidation methods have been reported early on. This review's vision emphasizes the emerging methods of N-N bond formation, particularly photo, electro, organo and transition metal free chemical methods.

Characterization of crystalline and amorphous forms of irbesartan by multi-nuclear solid-state NMR

Irbesartan (IRB) is an antihypertensive drug which exhibits the rare phenomenon of desmotropy; its 1H- and 2H- tetrazole tautomers can be isolated as distinct crystalline forms. The crystalline forms of IRB are poorly soluble, hence the amorphous form is potentially of interest for its faster dissolution rate. The tautomeric form and the nature of hydrogen bonding in amorphous IRB are unknown. In this study, crystalline form A and amorphous form of irbesartan were studied using ¹³C, ¹⁵N and ¹H solid-state NMR. Variable-temperature ¹³C SSMNR studies showed alkyl chain disorder in the crystalline form of IRB, which may explain the conflicting literature crystal structures of form A (the marketed form). ¹⁵N NMR indicates that the amorphous material contains an approximately 2:1 ratio of 1H- and 2H-tetrazole tautomers. Static ¹H SSNMR and relaxation time measurements confirmed different molecular mobilities of the samples and provided molecular-level insight into the nature of the glass transition. SSNMR is shown to be a powerful technique to investigate the solid state of disordered active pharmaceutical ingredients.

Synthesis of Novel Pyrazolo[3,4-b]pyridines with Affinity for β-Amyloid Plaques

Three novel pyrazolo[3,4-b]pyridines were synthesized via the cyclization of 5-amino-1-phenylpyrazole with the corresponding unsaturated ketone in the catalytic presence of ZrCl4. The ketones were afforded by modifying a stabilized ylide facilitated Wittig reaction in fairly high yields. The novel compounds exhibited exciting photophysical properties with the dimethylamine phenyl-bearing pyrazolopyridine showing exceptionally large Stoke’s shifts. Finally, both the dimethylamino- and the pyrene-substituted compounds demonstrated high and selective binding to amyloid plaques of Alzheimer’s disease (AD) patient brain slices upon fluorescent confocal microscopy observation. These results reveal the potential application of pyrazolo[3,4-b]pyridines in the development of AD amyloid plaque probes of various modalities for AD diagnosis.

N N ‑

The use of electricity as a traceless oxidant enables a sustainable and novel approach to N,N′-disubstituted indazolin-3-ones by an intramolecular anodic dehydrogenative N–N coupling reaction. This method is characterized by mild reaction conditions, an easy experimental setup, excellent scalability, and a high atom economy. It was used to synthesize various indazolin-3-one derivatives in yields up to 78%, applying inexpensive and sustainable electrode materials and a low supporting electrolyte concentration. Mechanistic studies, based on cyclic voltammetry experiments, revealed a biradical pathway. Furthermore, the access to single 2-aryl substituted indazolin-3-ones by cleavage of the protecting group could be demonstrated.

A novel sustainable electrochemical synthetic route to N,N′-disubstituted indazolin-3-ones by direct anodic oxidation with mild reaction conditions, a simple galvanostatic setup, broad scope and excellent scalability is established.

One-pot three-component synthesis of novel pyrazolo[3,4-b]pyridines as potent antileukemic agents

In the current study, we report on the development of novel series of pyrazolo[3,4-b]pyridine derivatives (8a-u, 11a-n, and 14a,b) as potential anticancer agents. The prepared pyrazolo[3,4-b]pyridines have been screened for their antitumor activity in vitro at NCI-DTP. Thereafter, compound 8a was qualified by NCI for full panel five-dose assay to assess its GI₅₀, TGI and LC₅₀ values. Compound 8a showed broad-spectrum anti-proliferative activities over the whole NCI panel, with outstanding growth inhibition full panel GI₅₀ (MG-MID) value equals 2.16 μM and subpanel GI₅₀ (MG-MID) range: 1.92-2.86 μM. Furthermore, pyrazolo[3,4-b]pyridines 8a, 8e-h, 8o, 8u, 11a, 11e, 11h, 11l and 14a-b were assayed for their antiproliferative effect against a panel of leukemia cell lines (K562, MV4-11, CEM, RS4;11, ML-2 and KOPN-8) where they possessed moderate to excellent anti-leukemic activity. Moreover, pyrazolo[3,4-b]pyridines 8o, 8u, 14a and 14b were further explored for their effect on cell cycle on RS4;11 cells, in which they dose-dependently increased populations of cells in G2/M phases. Finally we analyzed the changes of selected proteins (HOXA9, MEIS1, PARP, BcL-2 and McL-1) related to cell death and viability in RS4;11 cells via Western blotting. Collectively, the obtained results suggested pyrazolo[3,4-b]pyridines 8o, 8u, 14a and 14b as promising lead molecules for further optimization to develop more potent and efficient anticancer candidates.

Synthesis of Purines and Related Molecules by Cyclization ­Reactions of Heterocyclic Enamines

A great variety of pharmacologically relevant fluorinated purine analogues are available by cyclization reactions of heterocyclic enamines with 1,3-dielectrophiles. The reactions usually proceed with excellent regioselectivities. As electrophiles, 1,3-diketones, enaminones or 3-chloro-2-en-1-ones were used. Other synthetic strategies are based on inverse-electron-demand Diels–Alder reactions of heterocyclic enamines with triazines. Purine analogues were further functionalized by transition-metal-catalyzed CH-coupling reactions or oxidative cyclizations, giving rise to more complex polycyclic products. Amidino-C-glycosides in their reactions with 1,3-dielectrophiles afforded pyrimidine-C-glycosides. Multicomponent reactions of heterocyclic enamines afforded complex products, including spirocyclic derivatives.

1 Introduction

2 1,3-Diketones

3 Enaminones

4 3-Chloro-2-en-1-ones

5 Triazines

6 Transition-Metal-Catalyzed Functionalizations

7 Pyrimidine-C-Nucleosides

8 Multicomponent Reactions

9 Conclusions

Serum anti-AP3D1 antibodies are risk factors for acute ischemic stroke related with atherosclerosis

Atherosclerosis has been considered as the main cause of morbidity, mortality, and disability worldwide. The first screening for antigen markers was conducted using the serological identification of antigens by recombinant cDNA expression cloning, which has identified adaptor-related protein complex 3 subunit delta 1 (AP3D1) as an antigen recognized by serum IgG antibodies of patients with atherosclerosis. Serum antibody levels were examined using the amplified luminescent proximity homogeneous assay-linked immunosorbent assay (AlphaLISA) using a recombinant protein as an antigen. It was determined that the serum antibody levels against AP3D1 were higher in patients with acute ischemic stroke (AIS), transient ischemic attack, diabetes mellitus (DM), cardiovascular disease, chronic kidney disease (CKD), esophageal squamous cell carcinoma (ESCC), and colorectal carcinoma than those in the healthy donors. The area under the curve values of DM, nephrosclerosis type of CKD, and ESCC calculated using receiver operating characteristic curve analysis were higher than those of other diseases. Correlation analysis showed that the anti-AP3D1 antibody levels were highly associated with maximum intima-media thickness, which indicates that this marker reflected the development of atherosclerosis. The results of the Japan Public Health Center-based Prospective Study indicated that this antibody marker is deemed useful as risk factors for AIS.

In Silico Based Structural and Fingerprint Analysis of Structurally Diverse AT1 inhibitors

Background and Objective:

The development of pharmacologically active molecules for the treatment of hypertension and other cardiovascular diseases are important nowadays. In the present investigation, computational techniques have been implemented on Angiotensin II Type 1 (AT1) antagonists to develop better predictive models.

Methods:

Quantitative Structure Activity Relationship (QSAR) and structural patterns/fragments analyses were performed using physicochemical descriptors and MACCS Fingerprints calculaced from AT1 inhibitors collected from the literature.

Results:

The significant models developed have been validated by Leave One Out (LOO) and test set methods, which exhibit considerable Q2 values (>0.65 for the training set and >0.5 for the test set) and the R2pred values for the models are also >0.5. The applicability of the contributed descriptors in these models revealed that the chlorine atom, dipole moment, hydrogen bond donor atoms and electrostatic potential are negatively contributing, and the presence of bond between heavy atoms and the carbon atom connected with small side chain and topological polar vdW surface area are favorable for the AT1 antagonistic activity. The MACCS Fingerprints showed that the presence of atoms (kind of heavy atoms), such as N, O, and S, connected with other heteroatoms or carbon or any other atoms, through single or double bonds are predominantly present in highly active molecules. The presence of halogens, long chain alkanes, halogenated alkanes, and sulfur atoms attached with nitrogen through any atoms are responsible for decreased AT1 antagonistic activity.

Conclusion:

The results have provided additional information on the structural patterns of the compounds based on its MACCS Fingerprints, which may be used for further characterization and design of novel AT1 inhibitors.

A B2(OH)4-Mediated Synthesis of 2-Substituted Indazolone and Its Application in a DNA-Encoded Library

Indazolone cores are among the most common structural components in medicinal chemistry and can be found in many biologically active molecules. In this report, a mild and efficient approach to 2-substituted indazolones via B₂(OH)₄-mediated reductive N-N bond formation is developed. This strategy features mild conditions, no request for a metal catalyst, and a wide scope for both aliphatic and aromatic amines. Meanwhile, this method was further successfully applied on DNA to construct indazolone cores for a DNA-encoded library. This will enable the production of a very attractive indazolone-cored library from simple amines and scaffolds, which will provide considerable diversity.

"On Water" Palladium Catalyzed Direct Arylation of 1H-Indazole and 1H-7-Azaindazole

The C3 direct arylation of 1H-indazole and 1H-7-azaindazole has been a significant challenge due to the lack of the reactivity at this position. In this paper, we describe a mild and an efficient synthesis of new series of C3-aryled 1H-indazoles and C3-aryled 1H-7-azaindazoles via a C3 direct arylation using water as solvent. On water, PPh₃ was effective as a ligand along with a lower charge of the catalyst Pd(OAc)₂ (5 mol%) at 100 °C, leading to C3-aryled 1H-indazoles or C3-aryled 1H-7-azaindazoles in moderate to good yields.

Davis-Beirut Reaction: Diverse Chemistries of Highly Reactive Nitroso Intermediates in Heterocycle Synthesis

Indazoles are an important class of nitrogen heterocycles because of their excellent performance in biologically relevant applications, such as in chemical biology and medicinal chemistry. In these applications, convenient synthesis using commercially available and diverse building blocks is highly desirable. Within this broad class, 2H-indazoles are relatively underexploited when compared to 1H-indazole, perhaps because of regioselectivity issues associated with the synthesis of 2H-indazoles. This Account describes our unfolding of the synthetic utility of the Davis-Beirut reaction (DBR) for the construction of 2H-indazoles and their derivatives; parallel unfoldings of mechanistic models for these interrelated N-N bond forming reactions are also summarized. The Davis-Beirut reaction is a robust method that exploits the diverse chemistries of a key nitroso imine or nitroso benzaldehyde intermediate generated in situ under redox neutral conditions. The resulting N-N bond-forming heterocyclization between nucleophilic and electrophilic nitrogens can be leveraged for the synthesis of multiple classes of indazoles and their derivatives, such as simple or fused indazolones, thiazolo-indazoles, 3-alkoxy-2H-indazoles, 2H-indazole N-oxides, and 2H-indazoles with various substitutions on the ring system or the nitrogens. These diverse products can all be synthesized under alkaline conditions and the various strategies for accessing these heterocycles are discussed. Alternatively, we have also developed methods involving mild photochemical conditions for the nitrobenzyl → aci-nitro → nitroso imine sequence. Solvent consideration is especially important for modulating the chemistry of the reactive intermediates in these reactions; the presence of water is critically important in some cases, but water's beneficial effect has a ceiling because of the alternative reaction pathways it enables. Fused 2H-indazoles readily undergo ring opening reactions to give indazolones when treated with nucleophiles or electrophiles. Furthermore, palladium-catalyzed cross coupling, the Sonagashira reaction, EDC amide coupling, 1,3-dipolar cycloadditions with nitrile oxides, copper-catalyzed alkyne-azide cycloadditions (click reaction), as well as copper-free click reactions, can all be used late-stage to modify 2H-indazoles and indazolones. The continued development and applications of the Davis-Beirut reaction has provided many insights for taming the reactivity of highly reactive nitro and nitroso groups, which still has a plethora of underexplored chemistries and challenges. For example, there is currently a limited number of nonfused 2H-indazole examples containing an aryl substitution at nitrogen. This is caused by relatively slow N-N bond formation between N-aryl imine and nitroso reactants, which allows water to add to the key nitroso imine intermediate causing imine bond cleavage to be a competitive reaction pathway rather than proceeding through the desired N-N bond-forming heterocyclization.

Rapid and halide compatible synthesis of 2-N-substituted indazolone derivatives via photochemical cyclization in aqueous media

A straightforward protocol for the rapid construction of privileged indazolone architectures suggests a new avenue of great importance to medicinal chemistry.

Photochemical Preparation of 1,2-Dihydro-3 H-indazol-3-ones in Aqueous Solvent at Room Temperature

o-Nitrosobenzaldehyde is a reactive intermediate useful in the synthesis of nitrogen heterocycles. Previous strategies for using o-nitrosobenzaldehyde involve its isolation via chromatography and/or formation under harsh conditions. Herein, this intermediate was photochemically generated in situ from o-nitrobenzyl alcohols in a mild, efficient manner for the construction of 1,2-dihydro-3 H-indazol-3-ones using an aqueous solvent at room temperature. This convenient reaction offers several advantages over reported methods. The commercially available photoreactor employed 3 × 18 W bulbs outputting broad emission above 365 nm.

N-N Bond Formation between Primary Amines and Nitrosos: Direct Synthesis of 2-Substituted Indazolones with Mechanistic Insights

A concise, one-step route to indazolones from primary alkyl amines and o-nitrobenzyl alcohols is reported. The key step in this readily scalable indazolone forming process involves base-mediated in situ o-nitrobenzyl alcohol → o-nitrosobenzaldehyde conversion. Although this functional group interconversion is known to be useful for 2 H-indazole synthesis, its reactivity was modulated for indazolone formation.

Davis-Beirut Reaction: Alkoxide versus Hydroxide Addition to the Key o-Nitrosoimine Intermediate

Reaction options, alkoxide vs hydroxide vs amine addition to the key intermediate (o-nitrosoimine) generated in the Davis-Beirut reaction of an o-nitrobenzylamine substrate, are reported to explain the nucleophilic addition selectivity of this one-pot indazole-forming process. The hydroxide addition/deprotection pathway as well as the fate of the resulting o-nitrosobenzaldehyde were both uncovered with several o-nitrobenzylamine substrates, and design elements required for an efficient double Davis-Beirut reaction, inspired by new mechanistic insights, were defined.

Integration of multi-scale molecular modeling approaches with experiments for the in silico guided design and discovery of novel hERG-Neutral antihypertensive oxazalone and imidazolone derivatives and analysis of their potential restrictive effects on cell proliferation

AT1 antagonists is the most recent drug class of molecules against hypertension and they mediate their actions through blocking detrimental effects of angiotensin II (A-II) when acts on type I (AT1) A-II receptor. The effects of AT1 antagonists are not limited to cardiovascular diseases. AT1 receptor blockers may be used as potential anti-cancer agents - due to the inhibition of cell proliferation stimulated by A-II. Therefore, AT1 receptors and the A-II biosynthesis mechanisms are targets for the development of new synthetic drugs and therapeutic treatment of various cardiovascular and other diseases. In this work, multi-scale molecular modeling approaches were performed and it is found that oxazolone and imidazolone derivatives reveal similar/better interaction energy profiles compared to the FDA approved sartan molecules at the binding site of the AT1 receptor. In silico-guided designed hit molecules were then synthesized and tested for their binding affinities to human AT1 receptor in radioligand binding studies, using [¹²⁵I-Sar¹-Ile⁸] AngII. Among the compounds tested, 19d and 9j molecules bound to receptor in a dose response manner and with relatively high affinities. Next, cytotoxicity and wound healing assays were performed for these hit molecules. Since hit molecule 19d led to deceleration of cell motility in all three cell lines (NIH3T3, A549, and H358) tested in this study, this molecule is investigated in further tests. In two cell lines (HUVEC and MCF-7) tested, 19d induced G2/M cell cycle arrest in a concentration dependent manner. Adherent cells detached from the plates and underwent cell death possibly due to apoptosis at 19d concentrations that induced cell cycle arrest.

Structure-based design of hERG-neutral antihypertensive oxazalone and imidazolone derivatives

Angiotensin II receptor type 1 (AT1) antagonists are the most recent drug class against hypertension. Recently first crystal structure of AT1 receptor is deposited to the protein data bank (PDB ID: 4YAY). In this work, several molecular screening methods such as molecular docking and de novo design studies were performed and it is found that oxazolone and imidazolone derivatives reveal similar/better interaction energy profiles compared to the FDA approved sartan molecules at the binding site of the AT1 receptor. A database consisting of 3500-fragments were used to enumerate de novo designed imidazolone and oxazolone derivatives and hereby more than 50000 novel small molecules were generated. These derivatives were then used in high throughput virtual screening simulations (Glide/HTVS) to find potent hit molecules. In addition, virtual screening of around 18 million small drug-like compounds from ZINC database were screened at the binding pocket of the AT1 receptor via Glide/HTVS method. Filtered structures were then used in more sophisticated molecular docking simulations protocols (i.e., Glide/SP; Glide/XP; Glide/IFD; Glide/QPLD, and GOLD). However, the K⁺ ion channel/drug interactions should also be considered in studies implemented in molecular level against their cardiovascular risks. Thus, selected compounds with high docking scores via all diverse docking algorithms are also screened at the pore domain regions of human ether-a-go-go-related gene (hERG1) K⁺ channel to remove the high affinity hERG1 blocking compounds. High docking scored compounds at the AT1 with low hERG1 affinity is considered for long molecular dynamics (MD) simulations. Post-processing analysis of MD simulations assisted for better understanding of molecular mechanism of studied compounds at the binding cavity of AT1 receptor. Results of this study can be useful for designing of novel and safe AT1 inhibitors.

Four-component bicyclization approaches to skeletally diverse pyrazolo[3,4-b]pyridine derivatives

A novel four-component bicyclization strategy has been established, allowing a flexible and practical approach to 37 examples of multicyclic pyrazolo[3,4-b]pyridines from low-cost and readily accessible arylglyoxals, pyrazol-5-amines, aromatic amines, 4-hydroxy-6-methyl-2H-pyran-2-one, and cyclohexane-1,3-diones. The polysubstituted cyclopenta[d]pyrazolo[3,4-b]pyridines were stereoselectively synthesized through a microwave-assisted special [3+2+1]/[3+2] bicyclization with good control of the spatial configuration of exocyclic double bonds. The novel [3+2+1]/[2+2+1] bicyclization resulted in 17 examples of unreported pyrazolo[3,4-b]pyrrolo[4,3,2-de]quinolones. Reasonable mechanisms for forming two new types of multicyclic pyrazolo[3,4-b]pyridines are also proposed.

Facile and efficient syntheses of a series of N-benzyl and N-biphenylmethyl substituted imidazole derivatives based on (E)-urocanic acid, as angiotensin II AT1 receptor blockers

In the present work, a facile and efficient route for the synthesis of a series of N-substituted imidazole derivatives is described. Docking studies have revealed that N-substituted imidazole derivatives based on (E)-urocanic acid may be potential antihypertensive leads. Therefore, new AT1 receptor blockers bearing either the benzyl or the biphenylmethyl moiety at the N-1 or N-3 position, either the (E)-acrylate or the propanoate fragment and their related acids at the C-4 position as well as a halogen atom at the C-5 position of the imidazole ring, were synthesized. The newly synthesized analogues were evaluated for binding to human AT1 receptor. The biological results showed that this class of molecules possesses moderate or no activity, thus not always confirming high docking scores. Nonetheless, important conclusions can be derived for their molecular basis of their mode of action and help medicinal chemists to design and synthesize more potent ones. An aliphatic group as in losartan seems to be important for enhancing binding affinity and activity.

A systematic comparison of the properties of clinically used angiotensin II type 1 receptor antagonists

Angiotensin II type 1 receptor antagonists (ARBs) have become an important drug class in the treatment of hypertension and heart failure and the protection from diabetic nephropathy. Eight ARBs are clinically available [azilsartan, candesartan, eprosartan, irbesartan, losartan, olmesartan, telmisartan, valsartan]. Azilsartan (in some countries), candesartan, and olmesartan are orally administered as prodrugs, whereas the blocking action of some is mediated through active metabolites. On the basis of their chemical structures, ARBs use different binding pockets in the receptor, which are associated with differences in dissociation times and, in most cases, apparently insurmountable antagonism. The physicochemical differences between ARBs also manifest in different tissue penetration, including passage through the blood-brain barrier. Differences in binding mode and tissue penetration are also associated with differences in pharmacokinetic profile, particularly duration of action. Although generally highly specific for angiotensin II type 1 receptors, some ARBs, particularly telmisartan, are partial agonists at peroxisome proliferator-activated receptor-γ. All of these properties are comprehensively reviewed in this article. Although there is general consensus that a continuous receptor blockade over a 24-hour period is desirable, the clinical relevance of other pharmacological differences between individual ARBs remains to be assessed.

Rational design, efficient syntheses and biological evaluation of N,N'-symmetrically bis-substituted butylimidazole analogs as a new class of potent Angiotensin II receptor blockers

A series of symmetrically bis-substituted imidazole analogs bearing at the N-1 and N-3 two biphenyl moieties ortho substituted either with tetrazole or carboxylate functional groups was designed based on docking studies and utilizing for the first time an extra hydrophobic binding cleft of AT1 receptor. The synthesized analogs were evaluated for their in vitro antagonistic activities (pA2 values) and binding affinities (-logIC50 values) to the Angiotensin II AT1 receptor. Among them, the potassium (-logIC50 = 9.04) and the sodium (-logIC50 = 8.54) salts of 4-butyl-N,N'-bis{[2'-(2H-tetrazol-5-yl)biphenyl-4-yl]methyl}imidazolium bromide (12a and 12b, respectively) as well as its free acid 11 (-logIC50 = 9.46) and the 4-butyl-2-hydroxymethyl-N,N'-bis{[2'-(2H-tetrazol-5-yl)biphenyl-4-yl]methyl}imidazolium bromide (14) (-logIC50 = 8.37, pA2 = 8.58) showed high binding affinity to the AT1 receptor and high antagonistic activity (potency). The potency was similar or even superior to that of Losartan (-logIC50 = 8.25, pA2 = 8.25). On the contrary, 2-butyl-N,N'-bis{[2'-[2H-tetrazol-5-yl)]biphenyl-4-yl]methyl}imidazolium bromide (27) (-logIC50 = 5.77) and 2-butyl-4-chloro-5-hydroxymethyl-N,N'-bis{[2'-[2H-tetrazol-5-yl)]biphenyl-4-yl]methyl}imidazolium bromide (30) (-logIC50 = 6.38) displayed very low binding affinity indicating that the orientation of the n-butyl group is of primary importance. Docking studies of the representative highly active 12b clearly showed that this molecule has an extra hydrophobic binding feature compared to prototype drug Losartan and it fits to the extra hydrophobic cavity. These results may contribute to the discovery and development of a new class of biologically active molecules through bis-alkylation of the imidazole ring by a convenient and cost effective synthetic strategy.

A one-pot-three-step route to triazolotriazepinoindazolones from oxazolino-2H-indazoles

A one-pot-three-step method has been developed for the conversion of oxazolino-2H-indazoles into triazolotriazepinoindazolones with three points of diversity. Step one of this process involves a propargyl bromide-initiated ring opening of the oxazolino-2H-indazole (available by the Davis-Beirut reaction) to give an N(1)-(propargyl)-N(2)-(2-bromoethyl)-disubstituted indazolone, which then undergoes -CH(2)Br → -CH(2)N(3) displacement (step two) followed by an uncatalyzed intramolecular azide-alkyne 1,3-dipolar cycloaddition (step three) to form the target heterocycle. Employing 7-bromooxazolino-2H-indazole allows for further diversification through, for example, palladium-catalyzed coupling chemistry, as reported here.

The discovery of new potent non-peptide Angiotensin II AT1 receptor blockers: a concise synthesis, molecular docking studies and biological evaluation of N-substituted 5-butylimidazole derivatives

A convenient and facile synthesis, in silico docking studies and in vitro biological evaluation of N-substituted 5-butylimidazole derivatives as potent Angiotensin II (ANG II) receptor type 1 (AT1) blockers (ARBs) has been reported in the current study. Our efforts have been directed towards the development of an efficient synthetic route allowing the facile introduction of substituents on the imidazole ring. In particular, a series of imidazole based compounds bearing the biphenyl moiety at the N - 1 position, a halogen atom at the C-4 and polar substituents such as hydroxymethyl, aldo or carboxy group at the C-2 position were designed and synthesized. These compounds were evaluated for binding to human AT1 receptor and for ANG II antagonism in vitro on isolated rat uterus. Among them, 5-butyl-1-[[2'-(2H-tetrazol-5-yl)biphenyl-4-yl]methyl]imidazole-2-carboxylic acid (30) exhibited higher binding affinity compared to the other analogues tested (-log IC(50) = 8.46). The latter analogue was also found to be the most active in the rat uterotonic test (pA(2) = 7.83). Importantly, the binding affinity was higher to that of losartan (-log IC(50) = 8.25) indicating the importance of carboxy group at the C-2 position. Experimental findings are in good agreement with docking studies, which were undertaken in order to investigate ligand/AT1 receptor interactions.

Construction of pyrazolo[3,4-b]pyridines and pyrazolo[4,3-c]pyridines by ring closure of 3-acylpyridine N-oxide tosylhydrazones

3-Acylpyridine N-oxide tosylhydrazones give good overall yields of a mixture of pyrazolo[3,4-b]pyridines and pyrazolo[4,3-c]pyridines when treated with an electrophilic additive and an amine base. (Z)-Hydrazones cyclize readily, while (E)-hydrazones fail to react under the reported conditions. The reaction takes place at room temperature, and moderate regiocontrol over the cyclization can be achieved by varying the electrophile/solvent combination.

Synthesis and biological evaluation of novel potent angiotensin II receptor antagonists with anti-hypertension effect

A series of novel angiotensin II type 1 receptor antagonists were prepared. Radioligand binding assay suggested that compounds 1b and 1c could be recognized by the AT(1) receptor with an IC(50) value of 1.6 ± 0.09 nM and 2.64 ± 0.7 nM, respectively. In vivo anti-hypertension experiments showed that compounds (1a, 1b, 1c, 1e) elicited a significant decrease in SBP and DBP of spontaneous hypertensive rats (SHRs). The antihypertensive effects maintained for 10 h, which indicated that these compounds had a favorable blood pressure-lowering effect. Acute toxicity testing suggested that the LD(50) value of compound 1b was 2316.8 mg/kg which was lower than valsartan (LD(50)=307.50 mg/kg) but higher than losartan (LD(50)=2248 mg/kg). So they could be considered as novel anti-hypertension candidates and deserved for further investigation.