Design,Synthesis, Molecular Modeling Study,and Antimicrobial Activity of Some Novel Pyrano[2,3‐b]pyridine and Pyrrolo[2,3‐b]pyrano[2.3‐d]pyridine Derivatives

Novel derivatives of pyrano[2,3‐b]pyridine and pyrrolo[2,3‐b]pyrano[2.3‐d]pyridine were prepared, and their structures were elucidated by spectral and elemental analyses. The newly prepared candidates were evaluated for their antimicrobial activity against Candida sp., Aspergillus multi, Aspergillus niger, Escherichia coli, and Staphylococcus aureus. All the tested compounds revealed potent to moderate activity toward all tested microorganisms; especially, candidate 10 showed comparable antifungal activity as that showed by the standard drug ketoconazole toward Candida sp., and ethyl 4‐methyl‐1,7,8,9‐tetrahydropyrano[2,3‐b]pyrrolo[2,3‐d]pyridine‐3‐carboxylate ( 12 ) was the most active compound against all the tested bacteria. Furthermore, the newly synthesized compounds are subjected to molecular docking study for the inhibition of the enzyme L‐glutamine: D‐fructose‐6‐phosphate amidotransferase [GlcN‐6‐P], which is a new target for antimicrobials to explain action mode of these target compounds as leads for discovering other antimicrobial agents.     

Synthesis,characterization and antimicrobial screening of quinoline based quinazolinone-4-thiazolidinone heterocycles

In an attempt to find new pharmacologically active molecules, we report here the synthesis and in vitro antimicrobial activity of various 2-(2-chloro-6-methyl(3-quinolyl))-3-[2-(4-chlorophenyl)-4-oxo(3-hydroquinazolin-3-yl)]-5-[(aryl)methylene]-1,3-thiazolidin-4-ones. In vitro antimicrobial activity of the title compounds are screened against two Gram positive bacteria (Staphylococcus aureus, Streptococcus pyogenes), two Gram negative bacteria (Escherichia coli, Pseudomonas aeruginosa) and three strains of fungi (Candida albicans, Aspergillus niger, Aspergillus clavatus) using broth micro dilution method. Some derivatives bearing chloro or hydroxy group exhibited very good antimicrobial activity.     

Synthesis and Antimicrobial Studies of Selenadiazolo Benzimidazoles

An efficient and eco‐friendly method has been developed for the synthesis of selenadiazolo benzimidazoles by the condensation of N‐benzylbenzo[c][1,2,5]selenadiazole‐4,5‐diamine with various aromatic aldehydes catalyzed by xanthan sulfuric acid. All the synthesized compounds 5a , 5b , 5c , 5d , 5e , 5f , 5g , 5h , 5i , 5j were evaluated for in vitro antibacterial activity against Gram‐positive bacterial strains (Bacillus subtilis, Staphylococcus aureus, and Streptococcus pyogenes), and Gram‐negative bacterial strains (Escherichia coli, Klebsiella pneumonia, and Salmonella typhimurium) and antifungal against Aspergillus niger, Candida albicans, and Aspergillus flavus (Fungi). Compound 5i emerged as the most interesting compound in this series exhibiting excellent antimicrobial activity.     

Ultrasound‐Mediated Synthesis of Novel 1,2,3‐Triazole‐Based Pyrazole and Pyrimidine Derivatives as Antimicrobial Agents

In the development of novel antimicrobial agents, we synthesized novel 1,2,3‐triazole‐based pyrazole and pyrimidine derivatives 6 ( a–f ) and 7 ( a–f ) by ultrasound‐assisted method. The synthesized compounds were characterized by IR, ¹H NMR, ¹³C NMR, MS, and elemental analysis. All compounds were assessed in vitro for their efficacy as antimicrobial agents against four bacteria (Staphylococcus aureus , Bacillus subtilis , Escherichia coli , and Pseudomonas aeruginosa ) and two fungi (Candida albicans and Aspergillus niger ). In particular, compounds 6a , 6e , 7a , 7c , and 7e exhibited highly potent antimicrobial activity.     

Synthesis and Antifungal Screening of 2‐(2‐Aryl‐4‐methyl‐thiazol‐5‐yl)‐5‐((2‐aryl/benzylthiazol‐4‐yl)methyl)‐1,3,4‐oxadiazole Derivatives

A new series of synthesis and biological screening of 2‐(2‐aryl‐4‐methyl‐thiazol‐5‐yl)‐5‐((2‐aryl/benzylthiazol‐4‐yl)methyl)‐1,3,4‐oxadiazole derivatives 5a , 5b , 5c , 5d , 5e , 5f , 5g , 5h , 5i was achieved by condensation of 2‐(2‐aryl/benzylthiazol‐4‐yl)acetohydrazide 2a , 2b , 2c with 4‐methyl‐2‐arylthiazole‐5‐carbaldehyde 3a , 3b , 3c followed by oxidative cyclization of N'‐((4‐methyl‐2‐arylthiazol‐5‐yl)methylene)‐2‐(2‐aryl/benzylthiazol‐4‐yl)acetohydrazide 4a , 4b , 4c , 4d , 4e , 4f , 4g , 4h , 4i using iodobenzene diacetate as oxidizing agent. All the synthesized compounds were screened for their in vitro antifungal activity against Candida albicans, Candida tropicalis, Aspergillus niger, and Aspergillus flavus. Some of the synthesized compounds showed good antifungal activity.     

Synthesis and Antimicrobial Activity of New Thiazolidine‐Based Heterocycles as Rhodanine Analogues

A new series of compounds containing thiazole nucleus as Rhodanine analogues have been synthesized. The new compounds were prepared from the reactions of the thiosemicarbazones ( 3a,b ) with a series of α‐halo carbonyl compounds to give the corresponding Rhodanine analogues. The thiosemicarbazones derivatives ( 3a,b ) were reacted also with hydrazonoyl chlorides to afford the corresponding tri‐substituted and tetra‐substituted thiazoles. The structures of the newly synthesized compounds were confirmed by elemental analysis and spectral data. The biological activities of the new synthesized Rhodanine analogues' were evaluated for their antimicrobial activities. The results showed that some of these compounds showed excellent activity against two fungal strains, including Aspergillus niger and Aspergillus flavus, in addition to three yeast strains, including Saccharomyces cervesi, Candida albicans NRRL Y‐477, and Candida Pathological specimen compared with the ketoconazol, as the reference drug.     

Synthesis,spectroscopic studies,antimicrobial activity,and crystal structure of a Zn(II) complex based on Voriconazole

[Zn(FZ)₂Cl₂] (1) (FZ = Voriconazole, (2R,3S)-2-(2,4-difluorophenyl)-3(5-fluoropyrimidin-4-yl)-1-(1H-1,2,4-triazol-1-yl)butan-2-ol), has been obtained through the reaction of zinc chloride and FZ and has been characterized by FT-IR, UV–vis and fluorescence spectra, elemental analysis (EA), single crystal X-ray diffraction, powder X-ray diffraction and thermogravimetric analysis (TGA). FZ was also characterized by FT-IR, UV–vis spectra, single crystal X-ray diffraction and TGA. FZ crystallizes in the chiral space group P2₁ and 1 crystallizes in chiral space group P₁ with a mononuclear structure. In 1, there are three kinds of hydrogen bonding interactions and weak stacking interactions which generate a 3-D architecture. The primary antimicrobial results show that 1 exhibits potent activity against Aspergillus (Aspergillus niger, Aspergillus terreus, Aspergillus fumigatus and Aspergillus flavus) and Candida species (Candida albicans, Candida krusei, Candida glabrata and Cryptococcus neoformans), higher than that of free FZ. Fluorescence spectra of 1 and FZ have been discussed.     

Exploration of quinoxaline derivatives as antimicrobial and anticancer agents

Novel 2 and 3‐substituted quinoxaline derivatives were synthesized through various synthetic pathways, among which cyanoacetamide and cyanoacetohydrazide quinoxaline derivatives 4a‐c and 11a‐c , respectively, were synthesized. Furthermore, methoxy quinoxaline derivatives 3c and quinoxaline derivatives bearing substituted pyridines 6a,b , 12a,b , and 13a,b were designed to be synthesized. However, we have synthesized acrylohydrazide 5a,b and 7 /acrylamide derivatives, Schiff base analogues 14a‐f , pyrazole derivatives 15a‐e, amide derivatives 16a‐f , guanidine derivatives 16 g,h as well as, quinoxalin‐2‐methylallyl propionate derivative 14g . All the synthesized compounds were confirmed via spectral data and elemental analyses. Moreover, the newly synthesized compounds were evaluated for their antimicrobial activity (Gm +ve, Gm ?ve in comparison to Gentamycin a standard) and fungi (in comparison to Ketoconazole as a standard). Thus, compound 16b showed promising antimicrobial activity against B. subtilis, P. vulgaris, and S. mutants with values ranging from 20 to 27‐mm zone of inhibition. While compounds 5a , 14e,f, and 16a,c,d,g,h showed potent antimicrobial activity. Moreover, the National Cancer Institute (NCI) selected 20 compounds that were submitted for anticancer screening against 60 types of cancer cell lines. The most active compounds are 5b and 12a where compound 5b containing 2,4‐dichlorophenyl moiety at cyanoacetamide linkage of hydrazine quinoxaline backbone exerted significant growth inhibition activity against Leukemia MOLT‐4, Renal cancer UO‐31, and Breast cancer MCF‐7. In addition, compound 12a having 4,6‐diaminopyridinone side chain at position‐3 of quinoxaline nucleus exhibited remarkable anticancer activity against renal cancer UO‐31.     

Synthesis,Characterization, and Antimicrobial Studies of New Rigid Linker‐Based Bispyrazolines

The bispyrazolines 4a , 4b , 4c , 4d , 4e were synthesized from the cyclization reaction of bischalcones 3a , 3b , 3c , 3d , 3e with phenyl hydrazine by refluxing under alcoholic medium in the presence of glacial acetic acid. The bischalcones were obtained from the Claisen–Schmidt reaction of acetophenone with dibenzaldehydes 1a , 1b , 1c , 1d , 1e and later were obtained in good yield from the O‐alkylation of 4‐hydroxybenzaldehyde with suitable alkylating agents. The structures of the prepared compounds were determined from the rigorous analysis of their spectral data (UV–vis, IR, ¹H‐NMR, ¹³C‐NMR, and ESI‐MS). The elemental analysis also confirmed the purity of these compounds. All the bischalcones 3a , 3b , 3c , 3d , 3e and bispyrazolines 4a , 4b , 4c , 4d , 4e were screened for their antimicrobial activity using the serial dilution method. Seven bacterial and five fungal species were used as the antimicrobial test strains, namely Klebsiella pneumoniae (MTCC 3384), Pseudomonas aeruginosa (MTCC 424), Escherichia coli (MTCC 443), Staphylococcus aureus (MTCC 443), Bacillus subtilis (MTCC 441), Pseudomonas fluorescens (MTCC 103), and Staphylococcus pyrogens (MTCC 442), and Aspergillus janus (MTCC 2751), Penicillium glabrum (MTCC 4951), Fusarium oxysporum (MTCC 2480), Aspergillus sclerotiorum (MTCC 1008), and Aspergillus niger (MTCC 281), respectively. The minimum inhibitory concentrations (MIC in µg/mL) were determined by using different dilutions.     

Synthesis,Antimicrobial Activity and Molecular Docking Studies of 1,3‐Thiazole Derivatives Incorporating Adamantanyl Moiety

Synthesis, characterization and investigation of antimicrobial activity of 11 novel adamantanyl‐thiazoles are presented. Their structures were determined using ¹H and ¹³C NMR, EI(+)‐MS, HRMS, and elemental analyses. Among the derivatives, compound 3c showed very strong activity, especially against Candida albicans ATCC 10231 and Candida parapsilosis ATCC 22019 with minimal inhibitory concentration (MIC) values ranging from 1.95 to 7.81 µg/ml. Compounds 3a and 3b showed good antifungal activity. Among the examined compounds, the widest spectrum of antibacterial activity possessed 3f that showed good activity, especially against Staphylococcus epidermidis ATCC 12228, Micrococcus luteus ATCC 10240, Bacillus subtilis ATCC 6633 with MIC values ranging from 31.25 to 62.5 µg/ml. Molecular docking studies of all compounds on the active sites of microbial enzymes indicated possible targets sterol 14α‐demethylase, secreted aspartic proteinase (SAP), N‐myristoyltransferase (NMT), and topoisomerase II. Thiazoles 3a , 3b , 3c , 3d , 3e , 3f , 3g , 3h , 3i , 3j , 3k showed more favorable affinity to SAP and NMT than the native ligand.     

Synthesis,Characterization, and Biological Evaluation of Some Tri‐Substituted Imidazole/thiazole Derivatives

A novel compound series of tri‐substituted imidazole/thiazole derivatives ( 3a , 3b , 3c , 3d , 3e , 3f , 3g , 3h , 3i ) were prepared by Radziszewski reaction. Benzil ( 1 ), ammonium acetate or ammonium thiocynate, and 1‐phenyl‐3‐(p‐substituted phenyl)‐1H‐pyrazole‐4‐carbaldehyde ( 2a , 2b , 2c , 2d , 2e , 2f , 2g ) were reacted to give the desired product. Synthesized compounds were characterized by elemental analysis (CHNS) and spectral analysis (FTIR, ¹H and ¹³C FT NMR, and LC–MS). All the compounds were screened for their antibacterial, antifungal, and antimycobacterial activities. Antimicrobial activity was evaluated against some bacterial strains such as Escherichia coli (MTCC 443), Pseudomonas aeruginosa (MTCC 1688), Staphylococcus aureus (MTCC 96), Streptococcus pyogenes (MTCC 442), and the H₃₇Rv strain of Mycobacterium tuberculosis, and the fungal activity was observed against strains, for example, Candida albicans (MTCC 227), Aspergillus niger (MTCC 282), and Aspergillus clavatus (MTCC 1323). All the synthesized compounds were found to possess moderate to excellent activity against the above selected strains.     

Synthesis of novel thiazol-5-ylpyrimidine derivatives and their antimicrobial evaluation

Novel thiazol-5-ylpyrimidine derivatives were designed and synthesized. The chemical structures of all new synthesized compounds were assigned by studying their elemental analyses and spectral data (FT-IR, ¹HNMR, ¹³C NMR, and MS). The target compounds, 8 and 9a-9d were evaluated for their antimicrobial activity in vitro against gram-positive bacteria, Bacillus subtilis and Staphylococcus aureus, gram-negative bacteria, Salmonella abony and Escherichia coli and fungi, Aspergillus flavus and Fusarium oxysporum. In particular, compounds 9a-9c exhibited moderate to good activity against gram-positive bacteria, S. aureus, gram-negative bacteria, S. abony and fungus, Fusarium oxysporum in comparison with reference drugs.     

Synthesis,Antimicrobial, and Antioxidant Screening of Aryl Acetic Acid Incorporated 1,2,4‐Triazolo‐1,3,4‐Thiadiazole Derivatives

Some novel [1,2,4]triazolo[3,4‐b][1,3,4]thiadiazole derivatives were synthesized from aryl acetic acids. All the synthesized derivatives were selected for the screening of antibacterial potential against Gram‐positive bacteria [Staphylococcus aureus (MTCC 3160) and Micrococcus luteus (MTCC 1538)] and Gram‐negative bacteria [Escherichia coli (MTCC 1652) and Pseudomonas aeruginosa (MTCC 424)] and antifungal potential against Aspergillus niger (MTCC 8652) and Candida albicans (MTCC 227), and free radical scavenging activity through 2,2‐diphenyl‐2‐picrylhydrazyl hydrate method. The compounds TH‐4 , TH‐13 , and TH‐19 were found to be more potent antimicrobial agents compared to standard drugs. The compounds TH‐3 , TH‐9 , and TH‐18 also showed significant antimicrobial activity. The compound TH‐13 showed antioxidant activity with IC₅₀ value better than the standard compound. The structures of all the synthesized compounds were confirmed by Fourier transform infrared, ¹H‐NMR, liquid chromatography–mass spectrometry, and CHN analyzer.     

Synthesis and Antimicrobial Activities of Novel 2‐[substituted‐1H‐pyrazol‐4‐yl] Benzothiazoles,Benzoxazoles, and Benzimidazoles

In an endeavor to find a new class of antimicrobial agents, a series of novel substituted benzimidazole, benzoxazole, and benzothiazole derivatives 6 containing pyrazole moiety have been synthesized by reaction of 3‐aryl‐4‐formyl pyrazole 4 with substituted phenylenediamine or o‐aminophenol or o‐aminothiophenol 5 . Reaction of phenyl hydrazine or 2‐hydrazinopyridine 1 with substituted acetophenones 2 gave the corresponding hydrazones 3 , which on Vilsmeier–Haack reaction with POCl₃–DMF gave substituted 3‐aryl‐4‐formyl pyrazoles 4 . All final compounds 6a , 6b , 6c , 6d , 6e , 6f , 6g , 6h , 6i , 6j , 6k were evaluated for in vitro antibacterial activities against Escherichia coli and Staphylococcus aureus strains and in vitro antifungal activity against Candida albicans and Aspergillus niger strains by using serial dilution method. The antimicrobial activities were expressed as the minimum inhibitory concentration in µg/mL. The compound containing benzimidazole and benzoxazole moiety gave better antibacterial and antifungal activities than benzothiazole compounds.     

Synthesis,biological screening,in silico study and fingerprint applications of novel 1, 2, 4-triazole derivatives

A series of novel 1,2,4 triazole derivatives were synthesized by treating 4-bromo-2-(4H-1,2,4-triazole-3-yl)aniline (4) with different substituted benzene sulfonyl chlorides 5(a-f) and benzyl bromides 7(a-e) . IR, ¹H-NMR, ¹³C-NMR, and mass analysis confirmed the structures of the newly synthesized compounds. All derivatives were screened for their in vitro antibacterial activity against two bacterial strains viz Escherichia coli and Staphylococcus aureus, antifungal activity against Aspergillus flavus and Candida albicans, anthelmintic activity against Pheretima posthuma and also cytotoxicity activity against MDA-MB 231 and A375 cancer cell lines. It was found that some of the derivatives showed significant antibacterial, antifungal, anthelmintic, and cytotoxic activities when compared to respective standard drugs. Molecular docking studies have assisted the theoretical binding mode of the target molecules. Compounds were also explored for fingerprint application.     

Synthesis,spectral, thermal analyses,molecular modeling,and antimicrobial activities of Cu(II)-complexes with 1,3,4-oxadiazole Schiff-base derivatives

Seven Cu(II)-complexes with 2-amino-5-substituted aryl-1,3,4-oxadiazole Schiff bases are presented. The donors and possible geometries of the complexes were investigated by elemental and thermal (differential thermal analysis and thermogravimetric analysis) analyses, molar conductance, magnetic moments, IR, ¹H-NMR, ESR, UV-Vis, and mass spectra. The ligands are bidentate, coordinating through the nitrogen of azomethine and the nearest nitrogen to it. The results are supported by 3-D molecular modeling of 2 using CS Chem 3-D Ultra Molecular Modeling and Analysis Program. The investigated complexes have been screened for in-vitro antibacterial (Escherichia coli and Staphylococcus aureus) and antifungal (Aspergillus flavus and Candida albicans) activities. The qualitative and quantitative antimicrobial activities prove that the complexes are very active against the tested microorganisms.     

Ultrasound‐assisted Synthesis of Novel Pyrazole and Pyrimidine Derivatives as Antimicrobial Agents

Herein, we report a convenient and facile methodology for the synthesis of new series of pyrazole and pyrimidine derivatives 2a – f and 3a – f under ultrasound irradiation. Pyrazole and pyrimidine derivatives have been synthesized in better yields and shorter reaction times compared with the conventional method. The chemical structures of all the synthesized compounds were elucidated by their IR, ¹H NMR, ¹³C NMR, MS, and elemental analysis. Further, the target compounds were screened for their antimicrobial activity against four bacteria (Staphylococcus aureus, Bacillus subtilis, Escherichia coli, Pseudomonas aeruginosa) and two fungi (Candida albicans, Aspergillus niger). In particular, compounds 2a , 2d , 2e , 3a , 3e , and 3f exhibited potent antimicrobial activity.     

Synthesis of 5-phenyl-3-(10H-phenothiazinyl)-Δ2-cyclohexen-1-ones by conventional and microwave-assisted methods and their antifungal activity

A series of 5-phenyl-3-(10H-phenothiazinyl)-Δ²-cyclohexen-1-ones were prepared using conventional and microwave-assisted methods. The condensation between 3-phenyl-1-(10H-phenothiazinyl) prop-2-en-1-one derivatives (3a–g) and acetyl acetone yielded 5-phenyl-3-(10H-phenothiazinyl)-Δ²-cyclohexen-1-one derivatives (7a–g). The products were characterized by UV, IR, ¹H NMR, ¹³C NMR, 2D-NMR, MS, and elemental analysis. In vitro antifungal activity was carried out by zone of inhibition method against four species, namely Aspergillus niger, Candida albicans, Microsporum gypseum, and Aspergillus flavus. Compounds 7a and 7d showed good antifungal activity with zones of inhibition of 17 and 18 mm, respectively, and comparable with the standard substance, Bavinston, with 20 mm.     

Synthesis and antimicrobial activities of new 4,6‐diaryl‐ 4,5‐dihydro‐3‐hydroxy‐2H‐indazoles

A series of new 4,6‐diaryl‐4,5‐dihydro‐3‐hydroxy‐2H‐indazoles 5a , 5b , 5c , 5d , 5e , 5f , 5g , 5h , 5i , 5j , 5k were synthesized by the cyclization of ethyl 2‐oxo‐4,6‐diarylcyclohex‐3‐ene carboxylates 4a , 4b , 4c , 4d , 4e , 4f , 4g , 4h , 4i , 4j , 4k . The compounds were characterized by IR, ¹H NMR, ¹³C NMR, 2D NMR, and elemental analysis. The synthesized compounds were evaluated for in vitro antibacterial and antifungal activities against Staphylococcus aureus, Escherichia coli, Salmonella typhimurium, Pseudomonas aeruginosa, Candida albicans, Aspergillus niger, Aspergillus flavus, and Rhizopus sp. Most of the compounds exhibited good activity against the tested organisms. J. Heterocyclic Chem.,, (2012).     

Synthesis of antimicrobial azoloazines and molecular docking for inhibiting COVID-19

Diverse new azoloazines were synthesized from the reaction of fluorinated hydrazonoyl chlorides with heterocyclic thiones, 1,8-diaminonaphthalene, ketene aminal derivatives, and 4-amino-5-triflouromethyl-1,2,4-triazole-2-thiol. The mechanistic pathways and the structures of all synthesized derivatives were discussed and assured based on the available spectral data. The synthesized azoloazine derivatives were evaluated for their antifungal and antibacterial activities through zone of inhibition measurement. The results revealed promising antifungal activities for compounds 4 , 5 , 17a , b , 19 , and 25 against the pathogenic fungal strains used; Aspergillus flavus and Candida albicans compared to ketoconazole. In addition, compounds 4 , 5 , 19 , and 25 showed moderate antibacterial activities against most tested bacterial strains. Molecular docking studies of the promising compounds were carried out on leucyl-tRNA synthetase active site of Candida albicans, suggesting good binding in the active site forming stable complexes. Moreover, docking of the synthesized compounds was performed on the active site of SARS-CoV-2 3CLpro to predict their potential as a hopeful anti-COVID and to investigate their binding pattern.