Synthesis of acyclo-C-nucleosides in the imidazo[1,2-a]pyridine and pyrimidine series as antiviral agents

Unveiling the Reaction Mechanisms of the Synthesis and the Excited State Intramolecular Proton Transfer of 2-(2'-hydroxyphenyl)imidazo[1,2-a]pyridine

Given its wide variety of applications in the pharmaceutical industry, the synthesis of imidazo[1,2-a]pyridines has been extensively studied since the beginning of the last century. Here, we disclose the mechanism for the synthesis of imidazo[1,2-a]pyridines by means of the Ortoleva-King reaction. We also reveal the reaction pathway leading to the formation of a iodinated byproduct, demonstrating the challenge of preventing the formation of such a byproduct because of the low energy barrier to access it. Moreover, quantum chemistry tools were employed to investigate the mechanism of intramolecular proton transfer in the excited state, and connections with aromaticity were explored.

Anti-fungal effects of novel N-(tert-butyl)-2-(pyridin-2-yl)imidazo[1,2-a]pyridin-3-amine derivative and it's in-vitro, in-silico, and mode of action against Candida spp

Imidazoles are a category of azole antifungals that encompass compounds such as ketoconazole, miconazole, esomeprazole, and clotrimazole. In contrast, the triazoles group, which includes fluconazole, voriconazole, and itraconazole, also plays a significant role. The rise of antibiotic resistance in fungal pathogens has evolved into a substantial global public health concern. In this study, two newly synthesized imidazo[1,2-a]pyridine derivative (Probe I and Probe II) molecules were investigated for its antimicrobial potency against of a panel of bacterial (Gram-positive and Gram-negative bacteria) and fungal pathogens. Among the different types of pathogens, we found that Probe II showed excellent antifungal activity against fungal pathogens, based on the preliminary screening the potent molecule further investigated against multidrug-resistance Candida sp. (n = 10) and compared with commercial molecules. In addition, in-silico molecular docking, its dynamics, absorption, distribution, metabolism, excretion and toxicity (ADMET) were analyzed. In this study, the small molecule (Probe II) displayed potent activity only against the Candida spp. including several multidrug-resistant Candida spp. Probe II exhibited minimum inhibitory concentration ranges from 4 to 16 µg/mL and minimum fungicidal concentration in the range 4‒32 µg/mL as the lowest concentration enough to eliminate the Candida spp. The selected molecules inhibit the formation of yeast to mold as well as ergosterol formation by the computational simulation against Sterol 14-alpha demethylase (CYP51) and inhibition of ergosterol biosynthesis by in-vitro model show that the Probe II completely inhibits the formation of ergosterol in yeast cells at 2× MIC. The ADMET analysis Probe II could be moderately toxic to the human being, though the in-vitro toxicity studies will help to understand the real-time toxic level. The novel compound Probe II, which was synthesized during the study, shows promise for development into a new generation of drug treatments aimed at addressing the emerging drug resistance in Candida sp.

Synthesis of new imine-/amine-bearing imidazo[1,2-a]pyrimidine derivatives and screening of their cytotoxic activity

Imidazo[1,2-a]pyrimidine derivatives bearing imine groups (3a-e) were successfully synthesized in moderate to good yields using microwave-assisted heating. Corresponding amine derivatives (4a-e) were also obtained by the reduction reaction of the imine derivatives (3a-e). All synthesized products were characterized by FT-IR, 1H NMR, 13C NMR, and LC-MS spectroscopic techniques. In silico ADMET, Lipinski, and drug-likeness studies of the compounds were conducted and all were found to be suitable drug candidates. The cytotoxicity of the potential drug molecules was screened against the breast cancer cell lines MCF-7 and MDA-MB-231 and the healthy model HUVEC by the sulforhodamine B method. According to the antiproliferative studies, compounds 3d and 4d showed remarkable inhibition of MCF-7 cells with IC50 values of 43.4 and 39.0 μM and of MDA-MB-231 cells with IC50 values of 35.9 and 35.1 μM, respectively. In particular, compound 3d selectively inhibited the proliferation of MCF-7 1.6-fold and MDA-MB-231 2.0-fold relative to healthy cells. Moreover, the apoptotic mechanism studies indicated that compound 4d induced apoptosis by moderately increasing the ratio of Bax/Bcl-2 genes. Imidazo[1,2-a]pyrimidine derivative 3d, a promising cytotoxic agent, may be helpful in the discovery of new and more efficient anticancer agents for breast cancer treatment.

Design, synthesis, and computational studies of novel imidazo[1,2-a]pyrimidine derivatives as potential dual inhibitors of hACE2 and spike protein for blocking SARS-CoV-2 cell entry

In the present work, a new series of imidazo[1,2-a]pyrimidine Schiff base derivatives have been obtained using an easy and conventional synthetic route. The synthesized compounds were spectroscopically characterized using ¹H, ¹³C NMR, LC-MS(ESI), and FT-IR techniques. Green metric calculations indicate adherence to several green chemistry principles. The energy of Frontier Molecular Orbitals (FMO), Molecular Electrostatic Potential (MEP), Quantum Theory of Atoms in Molecules (QTAIM), and Reduced Density Gradient (RDG) were determined by the Density Functional Theory (DFT) method at B3LYP/6-31 G (d, p) as the basis set. Moreover, molecular docking studies targeting the human ACE2 and the spike, key entrance proteins of the severe acute respiratory syndrome coronavirus-2 were carried out along with hACE2 natural ligand Angiotensin II, the MLN-4760 inhibitor as well as the Cannabidiolic Acid CBDA which has been demonstrated to bind to the spike protein and block cell entry. The molecular modeling results showed auspicious results in terms of binding affinity as the top-scoring compound exhibited a remarkable affinity (-9.1 and -7.3 kcal/mol) to the ACE2 and spike protein respectively compared to CBDA (-5.7 kcal/mol), the MLN-4760 inhibitor (-7.3 kcal/mol), and angiotensin II (-9.2 kcal/mol). These findings suggest that the synthesized compounds may potentially act as effective entrance inhibitors, preventing the SARS-CoV-2 infection of human cells. Furthermore, in silico, ADMET, and drug-likeness prediction expressed promising drug-like characteristics.

The Dimroth Rearrangement in the Synthesis of Condensed Pyrimidines - Structural Analogs of Antiviral Compounds

The review discusses the use of the Dimroth rearrangement in the synthesis of condensed pyrimidines which are key structural fragments of antiviral agents. The main attention is given to publications over the past 10 years. The bibliography includes 107 references.

Sonication Assisted One-Pot Synthesis of Substituted Imidazopyridine from Styrene in Water

The present protocol is a simple and eco-friendly approach for the one-pot procedure for the synthesis of substituted imidazopyridines ranging from important feedstock's like styrene promoted by NBS. Through sonicator and microwave commercially available styrene with NBS in water followed by reaction with 2- aminopyridines afforded important heterocyclic scaffolds in an one-pot procedure.

La(OTf)3-catalysed one-pot synthesis of pyrazole tethered imidazo[1,2-a]azine derivatives and evaluation of their light emitting properties

La(OTf)₃catalysed one-pot facile protocol has been unfolded towards diversity-oriented synthesis of highly fluorescent pyrazole C-3(5) tethered imidazo[1,2-a]azines.

Green Synthesis and Antimicrobial Activity of Some Novel N-Arylimidazo[1,2-a]pyrazine-2-Carboxamide Derivatives

The article deals with the synthesis of some novel N-arylimidazo[1,2-a]pyrazine-2-carboxamides (7a-l) by condensation reaction of imidazo[1,2-a]pyrazine-2-carboxylic acid (5) with different aliphatic/aromatic amines (6a-l) by using 1-methylimidazole, Mukaiyama’s reagent and 2-chloro-1-methylpyridinium iodide under microwave irradiation conditions. A new series of compounds 7 have been prepared from 2-iodopyrazine (1). Compound 1 on purged with ammonia gas in the presence of Cu2O and K2CO3 furnishes pyrazin-2-amine (2), which is treated with ethyl 3-bromo-2-oxopropanoate (3) to produce ethyl imidazo[1,2-a]pyrazine-2-carboxylate (4), which on hydrolysis with NaOH yields imidazo[1,2-a]pyrazine-2-carboxylic acid (5). The structures of the newly synthesized compounds have been elucidated on the basis of spectral (IR, 1H and 13C NMR and MS) and analytical data. Compounds 7a-l have also been screened for their antimicrobial activity. Some of the compounds exhibit promising antimicrobial activity

Highly Regioselective, Acid-Catalyzed, Three-Component Cascade Reaction for the Synthesis of 2-aminopyridine-Decorated Imidazo[1,2- a]pyridine

A highly regioselective acid-catalyzed three-component reaction of 2-aminopyridine and 3-phenylpropiolaldehyde for the construction of imidazo[1,2- a]pyridine has been developed. This strategy provides a broad range of substrates and represents an efficient approach to give various 2-aminopyridine-decorated imidazo[1,2- a]pyridine in good yields.

Efficient synthesis and preliminary biological evaluations of trifluoromethylated imidazo[1,2-a]pyrimidines and benzimidazo[1,2-a]pyrimidines

Fluoromethylated imidazo[1,2-a]pyrimidines and benzimidazo[1,2-a]pyrimidines were synthesized through Michael addition/intramolecular cyclization reaction by condensation of 2-amino imidazole derivatives with ethyl 4,4,4-trifluorobut-2-ynate and using C–O bond activation.

Novel bisthioether derivatives containing a 1,3,4-oxadiazole moiety: design, synthesis, antibacterial and nematocidal activities

BACKGROUND

The literature shows that bisthioether and 1,3,4-oxadiazole derivatives exhibit a wide variety of biological activities. In this study, a series of novel bisthioether derivatives containing a 1,3,4-oxadiazole moiety were synthesized and their antibacterial and nematocidal activities investigated.

RESULTS

Among the title compounds evaluated, compound 4f demonstrated the best antibacterial activities against rice bacterial leaf blight, rice bacterial leaf streak and citrus canker caused by Xanthomonas oryzae pv. oryzae (Xoo), Xanthomonas oryzae pv. oryzicola (Xoc) and Xanthomonas axonopodis pv. citri (Xac), with EC₅₀ values of 4.82, 11.15 and 16.57 µg mL^-1 , respectively, which were even better than those of thiodiazole copper and bismerthiazol. Meanwhile, compound 4f had better in vitro nematocidal activity against Caenorhabditis elegans at 48 h, with an LC₅₀ value of 2.89 µg mL^-1 , which was superior to those of ethoprophos and fosthiazate. In addition, greenhouse trials indicated that compound 4f was effective in reducing rice bacterial leaf blight relative to thiodiazole copper and bismerthiazol.

CONCLUSION

A series of novel bisthioether derivatives containing a 1,3,4-oxadiazole moiety were synthesized and bioassay results showed that compound 4f exhibited the best antibacterial and nematocidal activities. © 2017 Society of Chemical Industry.

Synthesis, Molecular Docking, and Antimycotic Evaluation of Some 3-Acyl Imidazo[1,2-a]pyrimidines

A series of 3-benzoyl imidazo[1,2-a]pyrimidines, obtained from N-heteroarylformamidines in good yields, was tested in silico and in vitro for binding and inhibition of seven Candida species (Candida albicans (ATCC 10231), Candida dubliniensis (CD36), Candida glabrata (CBS138), Candida guilliermondii (ATCC 6260), Candida kefyr, Candida krusei (ATCC 6358) and Candida tropicalis (MYA-3404)). To predict binding mode and energy, each compound was docked in the active site of the lanosterol 14α-demethylase enzyme (CYP51), essential for fungal growth of Candida species. Antimycotic activity was evaluated as the 50% minimum inhibitory concentration (MIC50) for the test compounds and two reference drugs, ketoconazole and fluconazole. All test compounds had a better binding energy (range: -6.11 to -9.43 kcal/mol) than that found for the reference drugs (range: 48.93 to -6.16 kcal/mol). In general, the test compounds showed greater inhibitory activity of yeast growth than the reference drugs. Compounds 4j and 4f were the most active, indicating an important role in biological activity for the benzene ring with electron-withdrawing substituents. These compounds show the best MIC50 against C. guilliermondii and C. glabrata, respectively. The current findings suggest that the 3-benzoyl imidazo[1,2-a]pyrimidine derivatives, herein synthesized by an accessible methodology, are potential antifungal drugs.

A Cu(ii)-promoted tandem decarboxylative halogenation and oxidative diamination reaction of 2-aminopyridines with alkynoic acids for the synthesis of 2-haloimidazo[1,2-a]pyridines

A copper-promoted cascade decarboxylative halogenation and oxidative diamination reaction sequence of 2-aminopyridines with alkynoic acids has been developed for the synthesis of 2-haloimidazo[1,2-a]pyridines. In this reaction, two C-N bonds and one C-halogen bond are formed in one pot, generating the desired products in good yields. This is the first report on the synthesis of 2-haloimidazo[1,2-a]pyridine derivatives from alkynoic acids.

Synthesis, biological evaluation and molecular modeling studies of imidazo[1,2-a]pyridines derivatives as protein kinase inhibitors

We report here the synthesis, the biological evaluation and the molecular modeling studies of new imidazo[1,2-a]pyridines derivatives designed as potent kinase inhibitors. This collection was obtained from 2-aminopyridines and 2-bromoacetophenone which afforded final compound in only one step. The bioactivity of this family of new compounds was tested using protein kinase and ATP competition assays. The structure-activity relationship (SAR) revealed that six compounds inhibit DYRK1A and CLK1 at a micromolar range. Docking studies provided possible explanations that correlate with the SAR data. The most active compound 4c inhibits CLK1 (IC50 of 0.7 μM) and DYRK1A (IC50 of 2.6 μM).

Copper supported on H+-modified manganese oxide octahedral molecular sieves (Cu/H-OMS-2) as a heterogeneous biomimetic catalyst for the synthesis of imidazo[1,2-a]-N-heterocycles

A combination of Cu and H-OMS-2 is employed to synthesize heterocycles through multistep oxidation under a low-energy pathway.

Mechanism of the gold(i)-catalyzed synthesis of imidazo-pyrimidines and imidazo-pyrazines via [3 + 2] dipolar cycloaddition: a DFT study

The mechanisms of gold(i)-catalyzed [3 + 2] cycloaddition reactions of pyridinium N-(heteroaryl)-aminides with alkynes have been investigated using DFT calculations.

A novel fluorescent sensor based on imidazo[1,2-a]pyridine for Zn2+

A novel chemosensorL1for the detection of Zn²⁺based on imidazo[1,2-a]pyridine in C₂H₅OH–H₂O (9 : 1, v/v) buffer solution was designed and synthesized.

Facile and Efficient One-Pot Synthesis of Highly Functionalised 1,2,3,5-Tetrahydroimidazo[1,2-A]Pyrimidines

The one-pot, three-component reaction between isocyanides, electron-deficient acetylenic esters and 2-amino-1-methyl-1H-imidazol-4(5H)-one efficiently leads to highly functionalised 1,2,3,5-tetrahydroimidazo[1,2-a]pyrimidines without any activation in excellent yields at room temperature.

Regioselective synthesis of pyrrolo[1,2-a]imidazoles and imidazo[1,2-a]-pyridines

A concise synthesis of pyrrolo[1,2-a]imidazoles and imidazo[1,2-a]-pyridines by regioselective aza-ene additions and regioselective cyclic–condensation reactions of HKAs with ethyl 3-benzoylacrylate derivatives under catalyst-free conditions.

Microwave-assisted synthesis of novel 2,3-disubstituted imidazo[1,2-a]pyridines via one-pot three component reactions

An expeditious one-pot, metal-free, three-component reaction of arylglyoxals, cyclic 1,3-dicarbonyls and 2-aminopyridines in the presence of molecular iodine under microwave irradiation is reported.

A copper-catalyzed multi-component reaction accessing fused imidazo-heterocycles via C–H functionalization

An efficient synthesis of fused imidazo-heterocycles is described using Cu(OTf)₂ in [bmim]BF₄ by the multi-component reaction of pyridin-2(1H)-one or thiazol/benzo[d]thiazol-2(3H)-ones with O-tosylhydroxyl amine and acetophenones under microwave irradiation.