Importance of Hybrid Catalysts toward the Synthesis of 5H-Pyrano[2,3-d]pyrimidine-2-ones/2,4-diones (Thiones)

Regioselective cyclocondensations with thiobarbituric acid: spirocyclic and azocine products, X-ray characterization, and antioxidant evaluation

Multicomponent cyclocondensations of 5-amino-3-methyl-1-phenyl-1H-pyrazole (AMPZ), thiobarbituric acid, and p-formaldehyde under conventional thermal heating or ultrasonic irradiation were studied. Treatment of the reaction mixture in ethanol in an ultrasonic bath for 3 h produced azocine compound 4b, while the same mixture in ethanol under reflux conditions for 15 h produced spiro compound 4a. This work encompasses intricate experimental details, X-ray diffraction measurements, and multifaceted computational analyses employing methods such as the density functional theory and Hirshfeld surface analysis. Crystallographic investigations revealed the molecular structure of the compound and clarified its interactions involving hydrogen bonds and weak intermolecular forces. This article describes the synthesis and characterization of a novel spirocyclic compound. The study also evaluated the antioxidant potential in vitro using the DPPH and ABTS methods. The results showed that these compounds showed the best free radical scavenging ability, even in very small amounts, and that even at very low concentrations, these compounds showed excellent radical scavenging potential. Surprisingly, these compounds exhibited strong (ABTS+) radical scavenging activities, mainly attributed to the HAT mechanism, indicating their potential as therapeutic agents. Facile multipurpose, three-component selective procedures for new spiroheterocycles have been proposed, presenting intriguing perspectives in the field of medicine, particularly in the field of antioxidants. The geometric values of the computationally optimized structure were calculated using the density functional theory in LC-BLYP/6-31(d), aligned with the X-ray diffraction data, reinforcing the precision of our findings.

QSAR, Antimicrobial, and Antiproliferative Study of (R/S)-2-Thioxo-3,4-dihydropyrimidine-5-carboxanilides

Owing to the significant contribution of three-dimensional (3D) field-based QSAR toward hit optimization and accurately predicting the activities of small molecules, herein, the 3D-QSAR, in vitro antimicrobial, molecular docking, and pharmacophore modeling studies of all the isolated (R/S)-2-thioxo-DHPM-5-carboxanilides exhibiting antimicrobial activity were carried out. The screening process was performed using 46 compounds, and the best-scoring model with the top statistical values was considered for bacterial and fungal targets Bacillus subtilis and Candida albicans. As a result of 3D-QSAR analysis, compound 4v-(S)- and 4v-(R)-isomers were found to be more potent compared to the standard drugs tetracycline and fluconazole, respectively. Furthermore, the enantiomerically pure isomers 4q, 4d', 4n, 4f', 4v, 4q', 4c, and 4p' were found to be more potent than tetracycline and fluconazole to inhibit the bacterial and fungal growth against B. subtilis, Salinivibrio proteolyticus, C. albicans, and Aspergillus niger, respectively. Molecular docking analysis shows that with the glide score of -10.261 kcal/mol, 4v-(R)-isomer was found to be more potent against the fungal target C. albicans and may target the 14-α demethylase than fluconazole. Furthermore, all compounds' antiproliferative activity results showed that 4o' exhibited GI50 values between 8.8 and 34 μM against six solid tumor cell lines. Following the greater potential of 4o' toward the HeLa cell line, its kinetics study and live cell imaging were carried out. These outcomes highlight the acceptance and safety as well as the potential of compounds as effective antiproliferative and antifungal agents.

Understanding 2-(Nitromethylene)hexahydropyrimidin-5-ol Reaction Processes and NMR Spectroscopy: A Theoretical and Experimental Investigation

Ketene dithioacetals have significant applications in various fields, including natural products, pharmaceuticals, agrochemicals, and corrosion inhibitors. These compounds are highly valued for their reactivity and ability to participate in a wide range of organic syntheses. In this context, the reaction between 1,3-diaminopropan-2-ol and 1,1-bismethylsulfanyl-2-nitroethylene has been studied experimentally and theoretically by using density functional theory (DFT) calculations. A theoretical mechanism of formation of two possible products, 2-(nitromethylene)hexahydropyrimidin-5-ol (with a six-membered heterocycle) and (2-(nitromethylene)oxazolidin-5-yl)methanamine (with a five-membered heterocycle), is for the first time predicted. The present DFT results indicate that both mechanisms are exothermic, with energy barriers approximately 20 kcal/mol higher than those of the reactants. Among the two, the formation of 2-(nitromethylene)hexahydropyrimidin-5-ol is energetically more favorable. This compound was synthesized and analyzed by different experimental techniques (IR, nuclear magnetic resonance (NMR), and high-resolution mass spectrometry). The 1H and 13C NMR chemical shifts of 2-(nitromethylene)hexahydropyrimidin-5-ol were calculated using the GIAO/B3LYP, showing good agreement with our experimental observations. These findings highlight an important match between experimental results and theoretical predictions, offering deeper insights into ketene dithioacetal reactions. The new data and contributions are expected to generate significant interest in future applications.

Acetic Acid-Driven One-Pot Synthesis of 4,7-dihydro-[1,2,3]thiadiazolo[5,4-b]pyridine-6-carboxamides and Pharmacological Evaluations

A diverse set of 4,7-dihydro-[1,2,3]thiadiazolo[5,4-b]pyridine-6-carboxamides 4(a-o) was synthesized via a one-pot reaction of 5-amino-[1,2,3]thiadiazole, various aromatic aldehydes, and different acetoacetanilides, using glacial acetic acid. The resulting compounds were obtained in moderate to good yields. All the newly synthesized compounds were evaluated for their antimicrobial activity. Among them, compound 4 e demonstrated superior efficacy against the Salinivibrio proteolyticus strain of Gram-negative bacteria compared to ciprofloxacin. Compound 4 d exhibited the highest potency against the fungal strain Candida albicans, surpassing amphotericin B. The physicochemical characteristics of 4 d and 4 e were assessed. According to docking analysis, DHTDAPy 4 e shows a higher binding affinity of -7.2 kcal/mol in the binding cavity of the receptor. These findings illustrate the safety, tolerability, and potency of the newly synthesized DHTDAPy compounds against fungal and bacterial infections.

Silver-catalyzed regioselective synthesis of pyrano heterocycles: a versatile route to samoquasine A derivatives

This study introduces a silver-catalyzed method for the efficient and regioselective synthesis of pyrano heterocycles, utilizing readily available alcohols and water as nucleophiles. The method demonstrates high efficiency, delivering excellent yields and selectivity, and is scalable to gram quantities while maintaining broad functional group tolerance. Notably, the synthesized pyrano[3,4-c]quinolines were successfully transformed into diverse samoquasine A derivatives, underscoring the method's applicability in natural product synthesis. This work represents a significant advancement in pyrano heterocycle synthesis, offering a practical route to valuable compounds with potential applications in pharmaceutical and chemical research.

Click-chemistry mediated synthesis of OTBN-1,2,3-Triazole derivatives exhibiting STK33 inhibition with diverse anti-cancer activities

There is a continuous and pressing need to establish new brain-penetrant bioactive compounds with anti-cancer properties. To this end, a new series of 4'-((4-substituted-4,5-dihydro-1H-1,2,3-triazol-1-yl)methyl)-[1,1'-biphenyl]-2-carbonitrile (OTBN-1,2,3-triazole) derivatives were synthesized by click chemistry. The series of bioactive compounds were designed and synthesized from diverse alkynes and N3-OTBN, using copper (II) acetate monohydrate in aqueous dimethylformamide at room temperature. Besides being highly cost-effective and significantly reducing synthesis, the reaction yielded 91-98 % of the target products without the need of any additional steps or chromatographic techniques. Two analogues exhibit promising anti-cancer biological activities. Analogue 4l shows highly specific cytostatic activity against lung cancer cells, while analogue 4k exhibits pan-cancer anti-growth activity. A kinase screen suggests compound 4k has single-digit micromolar activity against kinase STK33. High STK33 RNA expression correlates strongly with poorer patient outcomes in both adult and pediatric glioma. Compound 4k potently inhibits cell proliferation, invasion, and 3D neurosphere formation in primary patient-derived glioma cell lines. The observed anti-cancer activity is enhanced in combination with specific clinically relevant small molecule inhibitors. Herein we establish a novel biochemical kinase inhibitory function for click-chemistry-derived OTBN-1,2,3-triazole analogues and further report their anti-cancer activity in vitro for the first time.

Indole clubbed 2,4-thiazolidinedione linked 1,2,3-triazole as a potent antimalarial and antibacterial agent against drug-resistant strain and molecular modeling studies

In the face of escalating challenges of microbial resistance strains, this study describes the design and synthesis of 5-({1-[(1H-1,2,3-triazol-4-yl)methyl]-1H-indol-3-yl}methylene)thiazolidine-2,4-dione derivatives, which have demonstrated significant antimicrobial properties. Compared with the minimum inhibitory concentrations (MIC) values of ciprofloxacin on the respective strains, compounds 5a, 5d, 5g, 5l, and 5m exhibited potent antibacterial activity with MIC values ranging from 16 to 25 µM. Almost all the synthesized compounds showed lower MIC compared to standards against vancomycin-resistant enterococcus and methicillin-resistant Staphylococcus aureus strains. Additionally, the majority of the synthesized compounds demonstrated remarkable antifungal activity, against Candida albicans and Aspergillus niger, as compared to nystatin, griseofulvin, and fluconazole. Furthermore, the majority of compounds exhibited notable inhibitory effects against the Plasmodium falciparum strain, having IC50 values ranging from 1.31 to 2.79 μM as compared to standard quinine (2.71 μM). Cytotoxicity evaluation of compounds 5a-q on SHSY-5Y cells at up to 100 μg/mL showed no adverse effects. Comparison with control groups highlights their noncytotoxic characteristics. Molecular docking confirmed compound binding to target active sites, with stable protein-ligand complexes displaying drug-like molecules. Molecular dynamics simulations revealed dynamic stability and interactions. Rigorous tests and molecular modeling unveil the effectiveness of the compounds against drug-resistant microbes, providing hope for new antimicrobial compounds with potential safety.

A green bio-organic catalyst (taurine) promoted one-pot synthesis of (R/S)-2-thioxo-3,4-dihydropyrimidine(TDHPM)-5-carboxanilides: chiral investigations using circular dichroism and validation by computational approaches

Owing to the massive importance of dihydropyrimidine (DHPMs) scaffolds in the pharmaceutical industry and other areas, we developed an effective and sustainable one-pot reaction protocol for the synthesis of (R/S)-2-thioxo-DHPM-5-carboxanilides via the Biginelli-type cyclo-condensation reaction of aryl aldehydes, thiourea and various acetoacetanilide derivatives in ethanol at 100 °C. In this protocol, taurine was used as a green and reusable bio-organic catalyst. Twenty-three novel derivatives of (R/S)-TDHPM-5-carboxanilides and their structures were confirmed by various spectroscopy techniques. The aforementioned compounds were synthesized via the formation of one asymmetric centre, one new C-C bond, and two new C-N bonds in the final product. All the newly synthesized compounds were obtained in their racemic form with up to 99% yield. In addition, the separation of the racemic mixture of all the newly synthesized compounds was carried out by chiral HPLC (Prep LC), which provided up to 99.99% purity. The absolute configuration of all the enantiomerically pure isomers was determined using a circular dichroism study and validated by a computational approach. With up to 99% yield of 4d, this one-pot synthetic approach can also be useful for large-scale industrial production. One of the separated isomers (4R)-(+)-4S developed as a single crystal, and it was found that this crystal structure was orthorhombic.