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The cyclooxygenase-2 (COX-2) enzyme is an important target for drug discovery and development of novel anti-inflammatory agents. Selective COX-2 inhibitors have the advantage of reduced side-effects, which result from COX-1 inhibition that is usually observed with nonselective COX inhibitors. In this study, the design and synthesis of a new series of 7-methoxy indolizines as bioisostere indomethacin analogues (5a–e) were carried out and evaluated for COX-2 enzyme inhibition. All the compounds showed activity in micromolar ranges, and the compound diethyl 3-(4-cyanobenzoyl)-7-methoxyindolizine-1,2-dicarboxylate (5a) emerged as a promising COX-2 inhibitor with an IC50 of 5.84 µM, as compared to indomethacin (IC50 = 6.84 µM). The molecular modeling study of indolizines indicated that hydrophobic interactions were the major contribution to COX-2 inhibition. The title compound diethyl 3-(4-bromobenzoyl)-7-methoxyindolizine-1,2-dicarboxylate (5c) was subjected for single-crystal X-ray studies, Hirshfeld surface analysis, and energy framework calculations. The X-ray diffraction analysis showed that the molecule (5c) crystallizes in the monoclinic crystal system with space group P 21/n with a = 12.0497(6)Å, b = 17.8324(10)Å, c = 19.6052(11)Å, α = 90.000°, β = 100.372(1)°, γ = 90.000°, and V = 4143.8(4)Å3. In addition, with the help of Crystal Explorer software program using the B3LYP/6-31G(d, p) basis set, the theoretical calculation of the interaction and graphical representation of energy value was measured in the form of the energy framework in terms of coulombic, dispersion, and total energy.

A simple and efficient method has been developed for construction of 3-(2-(1,3,4-thiadiazol-2-ylamino)acetyl)-2H-selenopyrano[2,3-b]quinolin-2-ones (3a–f). The 3-acetyl-2H-selenopyrano[2,3-b]quinolin-2-ones (1a–f) on bromination with glacial acetic acid offered 3-(2-bromoacetyl)-2H-selenopyrano[2,3-b]quinolin-2-ones (2a–f), these intermediates undergoes coupling with 1,3,4-thiadiazol-2-amine in the presence of potassium carbonate in dimethylformamide to get the title compounds. The present methodology provides an attractive approach to various substituted 3-acetyl-2H-selenopyrano[2,3-b]quinolin-2-ones ring with the 1,3,4-thiadiazol-2-amine heterocycle in one condensed molecule in moderate to good yields with favorable functional group tolerance, which has the advantages of operation simplicity, readily available starting materials, scale-up synthesis.

Synthesis and antimicrobial activities of novel S-5-(2-oxo-2H-selenopyrano [2,3-b]quinolin-3-yl)-1,3,4-oxadiazol-2-yl-2-cyanoethanethioates derivatives was undertaken employing a convenient and easily accessible procedure. A Series of S-5-(2-oxo-2H-selenopyrano[2,3-b]quinolin-3-yl)-1,3,4-oxadiazol-2-yl 2-cyanoethanethioates are synthesized by a simple and efficient one-pot reaction of substituted 3-(5-mercapto-1,3,4-oxadiazol-2-yl)-2H-selenopyrano[2,3-b]quinolin-2-ones with 2-cyanoacetyl chloride and potassium carbonate in the presence dimethyl formamide as a solvent. This reaction sequence involves a nucleophilic substitution of -S-H of 1,2,3-oxadiazole with 2-cyanoacetyl chloride. The structures of all the synthesized products were confirmed with their elemental analysis, IR,1H NMR and mass spectral analysis. All the newly synthesized compounds (2a-f) were screened for in vitro antimicrobial activities (Minimum Inhibitory Concentration (MIC) of three (Staphylococcus aureus, Micrococcus roseus) and (Escherichia coli) by disk diffusion method using ampicillin as positive and Dimethylformamide (DMF) as negative control. The tested, compounds 2d and 2e were highly active against S. aureus-ATCC 25953 and M. roseus-NCTC 07523 (gram positive) and moderately active against E. coli-ATCC 25922 (gram negative), compound 2c was slightly active against M. roseus and E. coli. Compound 2e was slightly active against S. aureus and M. roseus and compounds 2a and 2b were slightly active against M. roseus.

Candida albicans, an opportunistic fungal pathogen, frequently colonizes immune-compromised patients and causes mild to severe systemic reactions. Only few antifungal drugs are currently in use for therapeutic treatment. However, evolution of a drug-resistant C. albicans fungal pathogen is of major concern in the treatment of patients, hence the clinical need for novel drug design and development. In this study, in vitro screening of novel putative pyrrolo[1,2-a]quinoline derivatives as the lead drug targets and in silico prediction of the binding potential of these lead molecules against C. albicans pathogenic proteins, such as secreted aspartic protease 3 (SAP3, 2H6T), surface protein β-glucanase (3N9K) and sterol 14-alpha demethylase (5TZ1), were carried out by molecular docking analyses. Further, biological activity-based QSAR and theoretical pharmacokinetic analysis were analyzed. Here, in vitro screening of novel analogue derivatives as drug targets against C. albicans showed inhibitory potential in the concentration of 0.4 µg for BQ-06, 07 and 08, 0.8 µg for BQ-01, 03, and 05, 1.6 µg for BQ-04 and 12.5 µg for BQ-02 in comparison to the standard antifungal drug fluconazole in the concentration of 30 µg. Further, in silico analysis of BQ-01, 03, 05 and 07 analogues docked on chimeric 2H6T, 3N9K and 5TZ1 revealed that these analogues show potential binding affinity, which is different from the therapeutic antifungal drug fluconazole. In addition, these molecules possess good drug-like properties based on the determination of conceptual Density Functional Theory (DFT)-based descriptors, QSAR and pharmacokinetics. Thus, the study offers significant insight into employing pyrrolo[1,2-a]quinoline analogues as novel antifungal agents against C. albicans that warrants further investigation.

A Series of hybrid 3-(5-mercapto-1,3,4-oxadiazol-2-yl)-2H-selenopyrano[2,3-b]quinolin-2-one derivatives (3a-f) were synthesized by the reaction of 2-oxo-2H-selenopyrano[2,3-b]quinoline-3-carbohydrazides (2a-f) with carbon disulphide and potassium hydroxide in the presence of ethanol as solvent. The intermediates 2-oxo-2H-selenopyrano[2,3-b]quinoline-3-carbohydrazides (2a-f) were obtained by the reaction of 2-oxo-2H-selenopyrano[2,3-b]quinoline-3-carboxylates (1a-f) with hydrazine hydrate in ethanol. These (1a-f) were synthesized from available literature method. All the newly synthesized derivatives have been characterized by IR, 1H NMR, 13C NMR spectral and elemental analysis.

The present work deals with synthesis and characterization of some of novel 2H-[1,4]oxaselenepino[5,6-b]quinolin-3(5H)-ones derivatives. A series of 2‑chloro-3-formylquinolines (2a-I) were synthesized from substituted acetanilides (1a-I) using available protocol method and a series of 2‑chloro-3-formylquinolines (2a-l) are converted into 3-formyl-2-selenoquinolines (3a-l) using NaHSe. The resulting 3-formyl-2-selenoquinolines (3a-l) on reduction with sodiumborohydride in methanol afforded a diversely functionalized primary alcoholic derivatives (4a-l). These (2-Hydroselenoquinolin-3-yl)methanols (4a-l) on reacts with chloroacetic acid in the presence of aqueous potassium hydroxide in ethanol gives 2-((3-(Hydroxymethyl)quinolin-2-yl)selanyl)aceticacids (5a-l) scaffolds. The title compounds (6a-l) were prepared by the cyclisation of (5a-l) scaffolds in the presence of P2O5 with dioxane as a solvent. The structures of all the newly synthesized compounds were elucidated on the basis of their elemental analysis, IR, 1H NMR,13C NMR and mass spectral data.

The present study involves the synthesis of substituted novel ethyl 2-oxo-2H-selenopyrano[2,3-b]quinoline-3-carboxylates (4a-f) by the reaction of 3-formyl-2-selenoquinolines (3a-f) with diethyl malanoate in the presence of piperidine. 3-Formyl-2-selenoquinolines (3a-f) were prepared by the action of NaHSe on substituted 2-chloroquinoline-3-carbaldehydes (2a-f). A series of 2-chloroquinoline-3-carbaldehydes (2a-f) were synthesized from substituted acetanilides (1a-f) using available protocol method. The structures of all the newly synthesized compounds were characterized by their elemental analysis, IR, 1H NMR, 13C-NMR and mass spectral data. All the newly synthesized compounds (4a-f) were evaluated for antimicrobial activities. Among the compounds tested, 4d and 4e were highly active against S. aureus and M. roseus.

In the present study, we have worked out a convenient route for the synthesis of new series of novel 3-acetyl-2H-selenopyrano[2,3-b]quinolin-2-ones (4a-f) by the cyclization of 3-formyl-2-selenoquinolines (3a-f) using ethyl acetoacetate in the presence of catalytic amount of piperidine in acetonitrile as a solvent. The structures of all the synthesized products were confirmed with their elemental analysis, IR, 1H NMR, 13C NMR and mass spectral analysis. All the newly synthesized compounds (4a-f) were screened for in vitro antibacterial activities of three (Staphylococcus aureus, Micrococcus roseus) and (Escherichia coli) by disk diffusion method using ampicillin as positive and Dimethylformamide (DMF) as negative control. The tested, compounds 4d and 4e were highly active against S. aureus and M. roseus (gram positive) and moderately active against E. coli (gram negative), compound 4c was slightly active against M. roseus and E. coli. Compound 4e was slightly active against S. aureus and M. roseus and compounds 4a and 4b were slightly active against M. roseus.