3,4-Dimethyl-2,5-functionalized thieno[2,3-b]thiophenes: versatile precursors for novel bis-thiazoles

Novel Scaffolds Based on Bis-thiazole Connected to Quinoxaline or Thienothiophene through 2-Phenoxy-N-arylacetamide Groups as New Hybrid Molecules: Synthesis, Antibacterial Activity, and Molecular Docking Investigations

The resistance of microorganisms to antimicrobials has endangered the health of many people across the world. Overcoming the resistance problem will require the invention of molecules with a new mechanism of action so that no cross-resistance with existing therapies occurs. Because of their powerful antibacterial activity against a wide spectrum of Gram-positive and Gram-negative bacterial strains, heterocyclic compounds are appealing candidates for medicinal chemists. In this regard, as unique hybrid compounds, we synthesized a novel family of bis-thiazoles linked to quinoxaline or thienothiophene via the 2-phenoxy-N-arylacetamide moiety. The target compounds were synthesized by reacting the relevant bis(α-haloketones) with the corresponding thiosemicarbazones in EtOH at reflux with a few drops of TEA. Under comparable reaction conditions, the isomeric bis(thiazoles) were synthesized by reacting the appropriate bis(thiosemicarbazone) with the respective α-haloketones. The structures of the novel compounds were confirmed using elements and spectral data. All of the synthesized compounds were tested for antibacterial activity in vitro. With an inhibitory zone width of 12 mm, compound 12a had the same activity as the reference medication tobramycin against Staphylococcus aureus. Compound 12b showed 20 mg/mL as a minimum inhibitory concentration (MIC) against Bacillus subtilis. Some of the synthesized compounds were tested via molecular docking against two bacterial proteins (dihydrofolate reductase and tyrosyl-tRNA synthetase).

Oxygen- and Sulphur-Containing Heterocyclic Compounds as Potential Anticancer Agents

Oxygen- and sulphur-based heterocycles form the core structure of many biologically active molecules as well as U.S. FDA-approved drugs. Moreover, they possess broad range of biological activities, viz. anticancer, antiinflammatory, antioxidant, antitumour, antibacterial, antiviral, antidiabetic, anticonvulsant, anti-tubercular, analgesic, anti-leishmanial, antimalarial, antifungal, and anti-histaminic, Hence, O- and S-based heterocycles are gaining more attention in recent years on the road to the discovery of innovative anticancer drugs after the extensive investigation of nitrogen-based heterocycles as anticancer agents. Several attempts have been made to synthesize fused oxygen- and sulphur-based heterocyclic derivatives as joining one heterocyclic moiety with another may lead to improvement in the biological profile of a molecule. Humans have been cursed with cancer since long time. Despite the development of several heterocyclic anticancer medications such as 5-fluorouracil, doxorubicin, methotrexate, and daunorubicin, cure of cancer is difficult. Hence, researchers are trying to synthesize new fused/spiro heterocyclic molecules to discover novel anticancer drugs which may show promising anticancer effects with fewer side effects. Furthermore, fused heterocycles behave as DNA intercalating agents which have the ability to interact with DNA, leading to cell death thereby exerting anticancer effect. This review article highlights the synthesis and anticancer potentiality of oxygen- and sulphur-containing heterocyclic compounds covering the period from 2011 to 2021.

Hantzsch-like synthesis of novel bis(hexahydroacridine-1,8-diones), bis(tetrahydrodipyrazolo[3,4-b:4′,3′-e]pyridines), and bis(pyrimido[4,5-b]quinolines) incorporating thieno[2,3-b]thiophenes

A novel series of bis(hexahydroacridine-1,8-diones), bis(tetrahydrodipyrazolo[3,4- b:4′,3′- e]pyridines), and bis(pyrimido[4,5- b]quinolines) incorporating a thieno[2,3- b]thiophene core via ether or ester linkages is prepared via a Hantzsch-like reaction.

Synthesis, in-vitro and in-silico study of novel thiazoles as potent antibacterial agents and MurB inhibitors

Efficient procedures are herein reported for the synthesis of novel hybrid thiazoles via a one-pot three-component protocol. The protocol involves the reaction of novel aldehyde, thiosemicarbazide and halogen-containing reagents in solvent- and catalyst-free conditions. The structures of the new thiazoles were elucidated by elemental analyses and spectroscopic data. The in-vitro antibacterial screening and MurB enzyme inhibition assays were performed for the novel thiazoles. The thiazol-4(5H)-one derivative 6d, with p-MeO, exhibits the best antibacterial activities with minimum inhibitory concentration values of 3.9, 3.9, 7.8, and 15.6 μg/ml against Staphylococcus aureus, Klebsiella pneumoniae, Streptococcus mutans, and Escherichia coli, respectively, as compared to the reference antibiotic drugs. It also exhibits the highest inhibition of the MurB enzyme with an IC₅₀ of 8.1 μM. The structure-activity relationship was studied to determine the effect of the structures of the newly prepared molecules on the strength of the antibacterial activities. Molecular docking was also performed to predict the binding modes of the new thiazoles in the active sites of the E. coli MurB enzyme.

Synthesis of novel star-shaped molecules based on a 1,3,5-triazine core linked to different heterocyclic systems as novel hybrid molecules

The synthesis of novel star-shaped compounds based on an s-triazine core and linked to hexahydroacridinediones, pyrimido[4,5-b]quinolones, 1H-isoquinolino[2,1-a]quinolines, tetrahydro-4H-chromenes, dihydropyrano[2,3-c]pyrazoles, thiazole, or benzothiazole as new hybrid molecules through Michael and Hantzsch reactions is reported. For this purpose, 2,4,6-tris(4-formylphenoxy)benzaldehyde was used as a versatile precursor.

The synthesis of novel star-shaped compounds based on an s-triazine core and linked to different heterocycles as new hybrid molecules through Michael and Hantzsch reactions is reported.

Synthesis, Cytotoxicity and Molecular Docking Simulation of Novel bis-1,4-Dihydropyridines Linked to Aliphatic or Arene Core via Amide or Ester-Amide Linkages

OBJECTIVE

Novel bis(1,4-dihydropyridine-3,5-dicarbonitrile) derivatives linked to aliphatic or aromatic cores via amide or ester-amide linkages were prepared and their structures were confirmed by several spectral tools.

METHODS

The synthesis of novel N,N'-(alkanediyl)bis(2-(2-(3,5-dicyano-2,6-dimethyl-1,4-dihydropyridin- 4-yl)phenoxy)acetamide) by acid-catalyzed condensation of the bis-aldehydes with four equivalents of 3-aminocrotononitrile was reported.

RESULTS

The structures of the synthesized compounds were confirmed by different spectral tools. The molecular docking stimulation studies indicated that the prepared compounds bind to the active site of cellular inhibitor apoptotic protein (cIAP1-BIR3). MTT assay for the novel bis(1,4-dihydropyridines) was performed on two different human cell lines (A549 and HCT116).

CONCLUSION

Compound 5a showed higher cytotoxic activity against A549. Compound 5d showed moderate activity against HCT116. The rest of compounds indicated lower or no activity against both cell lines.

Facile synthesis of bis-thiosemicarbazone derivatives as key precursors for the preparation of functionalised bis-thiazoles

A new class of bis-thiosemicarbazones was designed and synthesised by the condensation of 2,6-diformylphenol derivatives and thiosemicarbazide using either ultrasound or conventional methods. Both thiosemicarbazone groups of these derivatives underwent a heterocyclisation process to give a series of novel bis-thiazole derivatives as major products. The structures of all the synthesised compounds were characterised by multinuclear NMR (1H and 13C), IR, HRMS and elemental analyses.

Synthesis, characterization and antitumor activity of novel tetrapodal 1,4-dihydropyridines: p53 induction, cell cycle arrest and low damage effect on normal cells induced by genotoxic factor H2O2

Synthesis of novel tetrakis(2,6-dimethyl-4-phenyl-1,4-dihydropyridinyl)methanes5a–dby acid-catalyzed condensation of the tetrakis-aldehydes6a–dwith eight equivalents of 3-aminobut-2-enenitrile2is reported. Antitumor activities of compounds5a–dwere also investigated.