Green synthesis, biological and spectroscopic study on the interaction of multi-component Mannich bases of imidazo[2,1-b]benzothiazoles with human serum albumin

Imidazopyrimidine: from a relatively exotic scaffold to an evolving structural motif in drug discovery

Nitrogen-fused heterocycles are of immense importance in modern drug discovery and development. Among them, imidazopyrimidine is a highly versatile scaffold with vast pharmacological utility. These compounds demonstrate a broad spectrum of pharmacological actions, including antiviral, antifungal, anti-inflammatory, and anticancer. Their adaptable structure allows for extensive structural modifications, which can be utilized for optimizing pharmacological effects via structure-activity relationship (SAR) studies. Additionally, imidazopyrimidine derivatives are particularly noteworthy for their ability to target specific molecular entities, such as protein kinases, which are crucial components of various cellular signaling pathways associated with multiple diseases. Despite the evident importance of imidazopyrimidines in drug discovery, there is a notable lack of a comprehensive review that outlines their role in this field. This review highlights the ongoing interest and investment in exploring the therapeutic potential of imidazopyrimidine compounds, underscoring their pivotal role in shaping the future of drug discovery and clinical medicine.

Synthesis of Benzo[4,5]thiazolo[2,3-c][1,2,4]triazole Derivatives via C-H Bond Functionalization of Disulfide Intermediates

Many nitrogen- and sulfur-containing heterocyclic compounds exhibit biological activity. Among these heterocycles are benzo[4,5]thiazolo[2,3-c][1,2,4]triazoles for which two main synthetic approaches exist. Here we report a new synthetic protocol that allows the preparation of these tricyclic compounds via the oxidation of a mercaptophenyl moiety to its corresponding disulfide. Subsequent C-H bond functionalization is thought to enable an intramolecular ring closure, thus forming the desired benzo[4,5]thiazolo[2,3-c][1,2,4]triazole. This method combines a high functional group tolerance with short reaction times and good to excellent yields.

Interaction between the Antimalarial Drug Dispiro-Tetraoxanes and Human Serum Albumin: A Combined Study with Spectroscopic Methods and Computational Studies

Dispiro-tetraoxanes, a class of fully synthetic peroxides which can be used as an antiplasmodial remedy for multiple drug-resistant strains of Plasmodium falciparum, were selected for the interaction study with human serum albumin (HSA). The insight into the interaction of the two chemically synthesized, most potent antimalarial tetraoxane analogues (TO1 and TO2) and HSA has been scrutinized using distinct spectroscopic techniques such as. UV-visible absorption, fluorescence, time-resolved fluorescence, and circular dichroism (CD). Fluorescence quenching experiments divulged the static mode of quenching and binding constants obtained (∼104) indicated the moderate affinity of the analogues to HSA. CD confirmed the conformational changes in the serum albumin upon interaction with these analogues. Molecular docking validated the empirical results as these two analogues bind through hydrophobic interactions and hydrogen bonding with HSA. Present work first defined the binding mechanism of dispiro-tetraoxanes with HSA and thus provides a fresh insight into the drug transportation and metabolism. The present study could direct toward designing more potent tetraoxane analogues for their use in the biomedical field.

Insight into the interaction of benzothiazole tethered triazole analogues with human serum albumin: Spectroscopy and molecular docking approaches

The interaction of four benzothiazole tethered triazole analogues (MS43, MS70, MS71, and MS78) with human serum albumin (HSA) was investigated using various spectroscopic techniques (ultraviolet-visible (UV-vis) light absorption, fluorescence, circular dichroism (CD), molecular docking and density functional theory (DFT) studies). Fluorescence quenching constants (~10¹² ) revealed a static mode of quenching and binding constants (K_b ~10⁴ ) indicating the strong affinity of these analogues for HSA. Further alteration in the secondary structure of HSA in the presence of these analogues was also confirmed by far UV-CD spectroscopy. The intensity loss in CD studied at 222 nm indicated an increase in random coil/β-sheet conformations in the protein. Binding energy values (MS71 (-9.3 kcal mol^-1 ), MS78 (-8.02 kcal mol^-1 ), MS70 (-7.16 kcal mol^-1 ) and MS43 (-6.81 kcal mol^-1 )) obtained from molecular docking revealed binding of these analogues with HSA. Molecular docking and DFT studies validated the experimental results, as these four analogues bind with HSA at site II through hydrogen bonding and hydrophobic interactions.

Efficient Access to Imidazo[1,2- a]pyridines/pyrazines/pyrimidines via Catalyst-Free Annulation Reaction under Microwave Irradiation in Green Solvent

An expeditious catalyst-free heteroannulation reaction for imidazo[1,2- a]pyridines/pyrimidines/pyrazines was developed in green solvent under microwave irradiation. Using H₂O-IPA as the reaction medium, various substituted 2-aminopyridines/pyrazines/pyrimidines underwent annulation reaction with α-bromoketones under microwave irradiation to provide the corresponding imidazo[1,2- a]pyridines/pyrimidines/pyrazines in excellent yields. The synthetic methodology appears to be very simple and superior to the already reported procedures with the high abundance of commercial reagents and great ability in expanding the molecular diversity. The present synthetic sequence is visualized as an environmentally benign process which allows the introduction of three points of structural diversity to expand chemical space with excellent purity and yields. The anti-inflammatory and antimicrobial activities of the derivatives were evaluated. Screening results uncovered three derivatives with strong inhibition of albumin denaturation and two derivatives were active on Proteus and Klebsiella bacteria. These positive bioassay results implied that the library of potential anti-inflammatory agents could be rapidly prepared in an ecofriendly manner, and provided new insights into drug discovery for medicinal chemists.

1,3-Di-n-butylimidazolium tribromide [BBim]Br3: An efficient recyclable catalyst mediated synthesis of N-substituted azepines and their biological evaluation-interaction study with human serum albumin

A majority of previously reported methods suffer from insufficient yields as well as more complicated experimental procedures, a smaller amount of isolated yields involving time-consuming and tiresome work-up with the use of metal catalyst and restricted scope of substrates. To overcome these issues, an environmentally benign, ionic liquid endorsed multi-component protocol to N-substituted azepines has been exploited by means of coupling aromatic amines, dimethyl/diethyl acetylene dicarboxylate, 2,5-dimethoxytetrahydrofuran using 1,3-Di-n-butylimidazolium tribromide [BBim]Br₃. The catalyst can be recycled and reused for subsequent reactions. The reactivated ionic liquid could be further reused twice as an accelerator All the synthesized compounds were further screened for their antimicrobial properties against three gram positive, four gram negative, and five fungal strains with chloromycin, norflaxacin, and fluconazole as reference drugs. Most of the tested compounds presented significant potency, especially, compound 4e displayed significant antibacterial activity (MIC=1-16μg/mL) whereas compound 4k showed momentous antifungal efficacy (MIC=2-32μg/mL). In addition binding behavior of compound 4e was investigated by binding study between calf thymus DNA and compound 4e by UV-Visible absorption spectroscopy and further research about HSA interactions were carried out. The observed wavelength showed a constancy thus revealing the occurrence of non-covalent π-π stacking interactions of compound 4e and HSA.