2-Aminopyridine - an unsung hero in drug discovery

Synthetic access to diverse thiazetidines via a one-pot microwave assisted telescopic approach and their interaction with biomolecules

A one-pot microwave assisted telescopic approach is reported for the chemo-selective synthesis of substituted 1,3-thiazetidines using readily available 2-aminopyridines/pyrazines/pyrimidine, substituted isothiocyanates and 1,2-dihalomethanes. The procedure involves thiourea formation from 2-aminopyridines/pyrazines/pyrimidine with the substituted isothiocyanates followed by a base catalysed nucleophilic attack of the CS bond on the 1,2-dihalomethane. Subsequently, a cyclization reaction occurs to yield substituted 1,3-thiazetidines. These four membered strained ring systems are reported to possess broad substrate scope with high functional group tolerance. The above synthetic sequence for the formation of four membered heterocycles is proven to be a modular and straightforward approach. Further the mechanistic pathway for the formation of 1,3-thiazetidines was supported by computational evaluations and X-ray crystallography analyses. The relevance of these thiazetidines in biological applications is evaluated by studying their ability to bind bio-macromolecules like proteins and nucleic acids.

Pd-NHC (NHC = N-Heterocyclic Carbene)-Catalyzed B-Alkyl Suzuki Cross-Coupling of 2-Pyridyl Ammonium Salts by N-C Activation: Application to the Discovery of Agrochemical Molecular Hybrids

2-Alkylpyridines are a privileged scaffold throughout the realm of organic synthesis and play a key role in natural products, pharmaceuticals, and agrochemicals. Herein, we report the first B-alkyl Suzuki cross-coupling of 2-pyridyl ammonium salts to access functionalized 2-alkylpyridines. The use of well-defined, operationally simple Pd-NHCs permits for an exceptionally broad scope of the challenging B-alkyl C-N cross-coupling with organoboranes containing β-hydrogen, representing a novel method for the discovery of highly sought-after molecules for plant protection.

Integral evaluation of effective conversion of sewage sludge from WWTP into highly porous activated carbon

Urban sewage sludge (SL) is a major concern due to the number of environmental problems it causes. Its application for different purposes is strictly regulated, limiting the possibilities of recycling and reusing this material. Thus, in this work, a complete study of a simple method to convert SL into activated carbon (AC) was carried out. The comprehensive study involves an evaluation of the main process parameters, such as the activating agent (AA) content (25 %, 33 %, 50 %), using the lowest amount of AA as novelty, different pyrolysis temperatures (600 and 800 °C), and purification conditions (6 M HCl:AC ratio, v:w). Under controlled and optimised conditions and through a single combined activation and pyrolysis step followed by acid purification, ACs with well-developed porosity can be obtained. Surface area values of around 870 m2/g and over 60 % carbon content were achieved, demonstrating that the prepared ACs could have applications in a wide variety of fields as high-value products. As an innovative aspect in this research, the gases streams and liquid effluents generated during the global process were analysed, achieving elimination of over 63 % of the concentration of the chemical elements contained in the SL during the chemical purification stage. Finally, mass, energy, and economic balances were carried out to estimate the production cost of AC derived from SL (<€ 8/kg AC).

Therapeutic and Diagnostic Agents based on Bioactive Endogenous and Exogenous Coordination Compounds

Metal-based coordination compounds have very special place in bioinorganic chemistry because of their different structural arrangements and significant application in medicine. Rapid progress in this field increasingly enables the targeted design and synthesis of metal-based pharmaceutical agents that fulfill valuable roles as diagnostic or therapeutic agents. Various coordination compounds have important biological functions, both those initially present in the body (endogenous) and those entering the organisms from the external environment (exogenous): vitamins, drugs, toxic substances, etc. In the therapeutic and diagnostic practice, both the essential for all living organisms and the trace metals are used in metal-containing coordination compounds. In the current review, the most important functional biologically active compounds were classified group by group according to the position of the elements in the periodic table.

Investigating the X-aminopyridine (X = 2 and 3) molecules sensing by Al12N12 and B12N12 fullerene-like nanocages: DFT, QTAIM, RDG and TD-DFT insights

DeThe adsorption of 2-aminopyridine (2-AP) and 3-aminopyridine (3-AP) on the external surface of B12N12 and Al12N12 fullerene-like nanocages (FLNs) is probed herein via DFT/M06-2X/6-311G(d,p) level of theory. It came out from the study that all FLN@X-AP states investigated are spontaneously formed. Moreover, topological analysis demonstrated that the boron nitride FLN can strongly adsorbed the APs through B-N covalent interactions. A significant change in the HOMO-LUMO band gap of B12N12, with values of 22.01 and 32.71% have been obtained following the adsorption of 2-AP and 3-AP respectively. Accordingly, the conductivity of B12N12 is greatly enhanced by the adsorption of the APs. The above mentioned observations, combined with those found from the analysis of dipole moments and molecular electrostatic potential maps predict B12N12 to be more sensitive to the aminopyridines investigated than the Al12N12 FLN from the theoretical point of view.Communicated by Ramaswamy H. Sarma.

Synthesis, density functional theory and kinetic studies of aminopyridine based α-glucosidase inhibitors

Aims: The current study aimed to develop new thiourea derivatives as potential α-glucosidase inhibitors for the management of hyperglycemia in patients of Type 2 diabetes, with a focus on identifying safer and more effective antidiabetic agents. Materials & methods: New thiourea derivatives (1-16) were synthesized through single-step chemical transformation and evaluated for in vitro α-glucosidase inhibition. Kinetic studies identified the mode of inhibition, free energy and type of interactions were analyzed through density functional theory and molecular docking. Results & conclusion: Compound 5 was identified as the most potent, noncompetitive and noncytotoxic inhibitor of α-glucosidase enzyme with a half-maximal inhibitory concentration of 24.62 ± 0.94 μM. Computational studies reinforce experimental results, demonstrating significant enzyme interactions via hydrophobic and π-π stacking forces.

Copper-Catalyzed Annulation of Electrophilic Benzannulated Heterocycles with 2-Aminopyridine and 2-Aminoquinoline: Direct Access toward Polyring-Fused Imidazo[1,2-a]pyridines

We have developed a direct method for the synthesis of polyring-fused imidazo[1,2-a]pyridines via a copper-catalyzed annulation of electrophilic benzannulated heterocycles with 2-aminopyridine and 2-aminoquinoline. From 3-nitroindoles and 2-aminopyridine, we could synthesize tetracenes, viz., indole-fused imidazo[1,2-a]pyridines, and by starting from 2-aminoquinoline, we could generate pentacenes, viz., indolo-imidazo[1,2-a]quinolines. In addition, we could also extend the methodology toward the synthesis of benzothieno-imidazo[1,2-a]pyridines starting from 3-nitrobenzothiophene. Furthermore, the basic photophysical properties of these synthesized heteroacenes were evaluated.

Molecular docking with SARS-CoV-2 and potential drug property of a bioactive novel Zn(II) polymer: A combined experimental and theoretical study

A new Zn(II) coordination polymer based on o-phthalato (Phth) and 2-aminopyridine (2-Ampy) viz. {[Zn(2-Ampy)₂(Phth)]∙(H₂O)]}_n (1) has been synthesized at room temperature and characterized by elemental analyses, electronic spectroscopy, FT-IR spectroscopy, thermal analysis (TGA/DSC), powder X-ray diffraction (PXRD) and single crystal X-ray diffraction. The basic trimeric units of 1 form a polymeric chain by N-H⋯O and π⋯π interactions. These polymeric chains interconnect through various non-covalent interactions in two perpendicular directions to ultimately give rise to a 3D architecture of 1. The interesting non-covalent interactions in 1, contributing to its stability in the solid state are studied by Hirshfeld surface analysis and other different theoretical tools. Molecular docking study of 1 is performed against six different proteins of SARS-CoV-2. The drug potential of the synthesized compound is evaluated by ADMET calculations.

In Silico Design and Investigation of Novel Thiazetidine Derivatives as Potent Inhibitors of PrpR in Mycobacterium tuberculosis

Tuberculosis is one of the most life-threatening acute infectious diseases diagnosed in humans. In the present investigation, a series of 16 new disubstituted 1,3-thiazetidines derivatives is designed, and investigated via various in silico methods for their potential as anti-tubercular agent by evaluating their ability to block the active site of PrpR transcription factor protein of Mycobacterium tuberculosis. The efficacy of the molecules was initially assessed with the help of AutoDock Vina algorithm. Further Glide module is used to redock the previously docked complexes. The binding energies and other physiochemical properties of the designed molecules were evaluated using the Prime-MM/GBSA and the QikProp module, respectively. The results of docking revealed the nature, site of interaction and the binding affinity between the proposed candidates and the active site of PrpR. Further the inhibitory effect of the scaffolds was predicted and evaluated employing a machine learning-based algorithm and was used accordingly. Further, the molecular dynamics simulation studies ascertained the binding characteristics of the unique 13, when analysed across a time frame of 100 ns with GROMACS software. The results show that the proposed 1,3-thiazetidine derivatives such as 10, 11, 13 and 14 could be potent and selective anti-tubercular agents as compared to the standard drug Pyrazinamide. Finally, this study concludes that designed thiazetidines can be employed as anti-tubercular agents. Undeniably, the results may guide the experimental biologists to develop safe and non-toxic drugs against tuberculosis by demanding further in vivo and in vitro analyses.

Synthetic approaches to potent heterocyclic inhibitors of tuberculosis: A decade review

Tuberculosis (TB) continues to be a significant global health concern with about 1.5 million deaths annually. Despite efforts to develop more efficient vaccines, reliable diagnostics, and chemotherapeutics, tuberculosis has become a concern to world health due to HIV, the rapid growth of bacteria that are resistant to treatment, and the recently introduced COVID-19 pandemic. As is well known, advances in synthetic organic chemistry have historically enabled the production of important life-saving medications that have had a tremendous impact on patients’ lives and health all over the world. Small-molecule research as a novel chemical entity for a specific disease target offers in-depth knowledge and potential therapeutic targets. In this viewpoint, we concentrated on the synthesis of a number of heterocycles reported in the previous decade and the screening of their inhibitory action against diverse strains of Mycobacterium tuberculosis. These findings offer specific details on the structure-based activity of several heterocyclic scaffolds backed by their in vitro tests as a promising class of antitubercular medicines, which will be further useful to build effective treatments to prevent this terrible illness.

Cu-Catalyzed Chan-Evans-Lam Coupling reactions of 2-Nitroimidazole with Aryl boronic acids: An effort toward new bioactive agents against S. pneumoniae

The coupling of phenylboronic acids with poorly-activated imidazoles is studied as a model system to explore the use of copper-catalyzed Chan-Evans-Lam (CEL) coupling for targeted C-N bond forming reactions. Optimized CEL reaction conditions are reported for four phenanthroline-based ligand systems, where the ligand 4,5-diazafluoren-9-one (dafo, L2 ) with 1 molar equivalent of potassium carbonate yielded the highest reactivity. The substrate 2-Nitroimidazole (also known as azomycin) has documented antimicrobial activity against a range of microbes. Here N-arylation of 2-nitroimidazole with a range of aryl boronic acids has been successfully developed by copper(II)-catalyzed CEL reactions. Azomycin and a range of newly arylated azomycin derivatives were screened against S. pneumoniae , where 1-(4-(benzyloxy)phenyl)-2-nitro-1H-imidazole ( 3d ) was demonstrated to have a minimal inhibition concentration value of 3.3 μg/mL.