Synthetic access to imidazo[2,1-b]thiazoles

Investigation of Ln3+ complexation by a DOTA derivative substituted by an imidazothiadiazole: synthesis, solution structure, luminescence and relaxation properties

We investigated the coordination properties of original macrocyclic Ln3+ complexes comprising an imidazothiadiazole heterocycle. The thermodynamic stability of the Gd3+ complex was determined by a combination of potentiometric and photophysical measurements. The kinetic inertness was assessed in highly acidic media. The solution structure of the Ln3+ complex was unambiguously determined by a set of photophysical measurements and 1H, 13C, 89Y NMR data in combination with DFT calculations, which proved coordination of the heterocycle to Ln3+. The ability of the imidazothiadiazole moiety to sensitize Tb3+ luminescence was investigated. Finally, the relaxation properties were investigated by recording 1H nuclear magnetic relaxation dispersion (NMRD) profiles and 17O measurements. The water exchange rate is similar to that of GdDOTA as the less negative charge of the ligand is compensated for by the presence of a bulky heterocycle. Relaxivity is constant over a large range of pH values, demonstrating the favorable properties of the complex for imaging purposes.

A newly synthesized thiosemicarbazide derivative trigger apoptosis rather than necroptosis on HEPG2 cell line

Thiosemicarbazide derivatives have been the focus of scientists owing to their broad biological activities such as anticancer, antimicrobial, and anti-inflammatory. Herein, we designed and synthesized a new thiosemicarbazide derivative (TS-1) and evaluated its antiproliferative potential against the human hepatocellular carcinoma cell line (HEPG2) and human umbilical vein endothelial cell line (ECV-304). Also, it was aimed to investigate the necroptotic and apoptotic cell death effects of TS-1 in HEPG2 cells, and these effects were supported by molecular docking. The new synthesized compound structure was characterized using various spectroscopic methods such as FT-IR, 1 H-NMR, 13 C-NMR, and elemental analysis. The cytotoxic activity of the tested compound was measured by the MTT assay. Apoptotic and necroptotic properties of the TS-1 were evaluated by indirect immunoperoxidase method using antibodies against Ki-67, Bax, Bcl-2, caspase-3, caspase-8, caspase-9, RIP3, and RIPK1. Apoptotic and necroptotic effects of TS-1 were supported by molecular docking. Compound TS-1 was synthesized as a pure compound with a high yield. The effective value of TS-1 was 10 μM in HEPG2 cells. TS-1 did not show any cytotoxic effect on ECV-304. Caspase-3 and RIPK1 immunoreactivities were significantly increased in HEPG2 cells after being treated with TS-1. As the results of the molecular docking studies, the molecular docking showed that the TS-1 exhibits H-bond interaction with various significant amino acid residues in the active site of both RIPK1. It could be concluded that TS-1 could be a promising novel therapeutic agent by inducing apoptosis rather than necroptosis in HEPG2 cells.

Visible light-promoted intermolecular cyclization/aromatization of chalcones and 2-mercaptobenzimidazoles via an EDA complex and a mechanism study

Visible-light-promoted cyclization and aromatization of chalcones with 2-mercaptobenzimidazoles have been successfully developed to obtain diverse imidazo[2,1-b]thiazoles, and C-S and C-N bonds were constructed in one step. The reaction uses oxygen in the air as an oxidant, and the method does not need an external photocatalyst or a transition metal catalyst. The strategy features mild conditions, a simple system, readily accessible feedstocks, and a friendly environment. UV absorption spectroscopy and control experiments have shown that the reaction mechanism involves the formation of an electron-donor-acceptor (EDA) complex from thiolate anions and chalcones. In order to verify the mechanism, we studied the structure and HOMO/LUMO of the EDA complex by density functional theory (DFT) calculations. The results show that the π-π stacking between chalcones and 2-mercaptobenzimidazoles will cause a red shift of the UV absorption wavelength in the presence of Cs₂CO₃, and also provide a theoretical basis for the electron transfer of EDA complexes.

An Insight into All Tested Small Molecules against Fusarium oxysporum f. sp. Albedinis: A Comparative Review

Bayoud disease affects date palms in North Africa and the Middle East, and many researchers have used various methods to fight it. One of those methods is the chemical use of synthetic compounds, which raises questions centred around the compounds and common features used to prepare targeted molecules. In this review, 100 compounds of tested small molecules, collected from 2002 to 2022 in Web of Sciences, were divided into ten different classes against the main cause of Bayoud disease pathogen Fusarium oxysporum f. sp. albedinis (F.o.a.) with structure-activity relationship (SAR) interpretations for pharmacophore site predictions as (δ^-···δ^-), where 12 compounds are the most efficient (one compound from each group). The compounds, i.e., (Z)-1-(1.5-Dimethyl-1H-pyrazole-3-yl)-3-hydroxy but-2-en-1-one 7, (Z)-3-(phenyl)-1-(1,5-dimethyl-1H-pyrazole-3-yl)-3-hydroxyprop-2-en-1-one 23, (Z)-1-(1,5-Dimethyl-1H-pyrazole-3-yl)-3-hydroxy-3-(pyridine-2-yl)prop-2-en-1-one 29, and 2,3-bis-[(2-hydroxy-2-phenyl)ethenyl]-6-nitro-quinoxaline 61, have antifungal pharmacophore sites (δ^-···δ^-) in common in N1---O4, whereas other compounds have only one δ^- pharmacophore site pushed by the donor effect of the substituents on the phenyl rings. This specificity interferes in the biological activity against F.o.a. Further understanding of mechanistic drug-target interactions on this subject is currently underway.

Synthesis of novel series of 3,5-disubstituted imidazo[1,2-d] [1,2,4]thiadiazoles involving SNAr and Suzuki–Miyaura cross-coupling reactions

The first access to 3,5-disubstituted imidazo[1,2-d][1,2,4]thiadiazole derivatives is reported. The series were generated from 2-mercaptoimidazole, which afforded the key intermediate bearing two functional positions. The S_NAr reactivity toward tosyl release at the C-3 position was investigated and a regioselective electrophilic iodination in C-5 position was performed to allow a novel C–C bond using Suzuki–Miyaura reaction. Palladium-catalyzed cross-coupling conditions were optimized. A representative library of various boronic acids was employed to establish the scope and limitations of the method. To complete this methodological study, the influence of the nature of the C-3 imidazo[1,2-d][1,2,4]thiadiazole substitutions on the arylation in C-5 was investigated.

A convenient design of 3,5-disubstituted imidazo[1,2-d][1,2,4]thiadiazoles is reported from 2-mercaptoimidazole, which afforded a versatile platform that was then used to access a variety of original heterocycles.

Ultrasound for Drug Synthesis: A Green Approach

This last century, the development of new medicinal molecules represents a real breakthrough in terms of humans and animal life expectancy and quality of life. However, this success is tainted by negative environmental consequences. Indeed, the synthesis of drug candidates requires the use of many chemicals, solvents, and processes that are very hazardous, toxic, energy consuming, expensive, and generates a large amount of waste. Many large pharmaceutical companies have thus moved to using green chemistry practices for drug discovery, development, and manufacturing. One of them is the use of energy-efficient activation techniques, such as ultrasound. This review summarizes the latest most representative works published on the use of ultrasound for sustainable bioactive molecules synthesis.

Solvent- and Catalyst-Free One-Pot Green Bound-Type Fused Bis-Heterocycles Synthesis via Groebke-Blackburn-Bienaymé Reaction/SNAr/Ring-Chain Azido-Tautomerization Strategy

A new, efficient, green, endogenous water-triggered, solvent- and catalyst-free ultrasound-assisted one-pot Groebke-Blackburn-Bienaymé reaction/S_NAr/ring-chain azido-tautomerization strategy to synthesize bound-type fused bis-heterocycles imidazo or benzo[d]imidazo[2,1-b]thiazoles and 1,5-disubstituted tetrazole (1,5-DsT) containing quinoline moiety is described, which allows synthesis of two types of fused heterocycles in one step under mild green conditions. Antibacterial and antiamebic activities of selected newly synthesized compounds were carried out against three bacterial species: Gram-positive bacterium Staphylococcus aureus ATCC 6538 and Gram-negative bacteria Pseudomonas aeruginosa ATCC 13384 and Escherichia coli O55 and against one amebic species: Entamoeba histolytica.