Synthesis and in vitro Antibacterial Activities of 5‐(2,3,4,5‐Tetrahydro‐1H‐chromeno[2,3‐d]pyrimidin‐5‐yl)pyrimidione Derivatives

A series of novel 5‐(2,3,4,5‐tetrahydro‐1H‐chromeno[2,3‐d]pyrimidin‐5‐yl)pyrimidione derivatives have been synthesized from substituted salicylaldehydes and barbituric acid or 2‐thiobarbituric acid in water catalyzed by phase transfer catalysis of triethylbenzyl ammonium chloride (TEBA). Elemental analysis, IR, ¹H NMR, and ¹³C NMR elucidated the structures of all the newly synthesized compounds. In vitro antimicrobial activities of synthesized compounds have been investigated against Escherichia coli, Bacillus subtilis, Staphylococcus aureus, and Pseudomonas aeruginosa. These newly synthesized derivatives exhibited significant in vitro antibacterial activity.     

Synthesis and in vitro Antimicrobial Activity of New Ethyl 2-(Ethoxyphosphono)-1-cyano-2-(substituted tetrazolo-[1,5-a]quinolin-4-yl)ethanoate Derivatives

A series of new ethyl 2‐(ethoxyphosphono)‐1‐cyano‐2‐(substituted tetrazolo[1,5‐a]quinolin‐4‐yl)ethanoate derivatives have been synthesized for the first time of tetrazolo[1,5‐a]quinoline derivatives. Elemental analysis, IR, ¹H NMR, ¹³C NMR, ³¹P NMR and mass spectral data elucidated the structures of the all newly synthesized compounds. In vitro antimicrobial activities of synthesized compounds have been investigated against Gram‐positive Bacillus subtilis, Gram‐negative Escherichia coli and two fungi Candida albicans and Aspergillus niger in comparison with standard drugs. Significantly microbiological behavior of these newly synthesized derivatives possesses significant antibacterial and antifungal activity.     

Effect of the lithium cation on the sorption and electrical properties of amphiphilic block copolymers and their composites

The use of lithium cation in composites of block copolymers [polyethylene‐b‐polyethylene oxide (PE‐b‐50%PEO and PE‐b‐80%PEO)] and their derivatives was tested as a modifier of the vapor sorption and impedance of these complexes. The block copolymer PE‐b‐80%PEO was modified by oxidation of its hydroxyl end group to both a carboxylic acid group (PE‐b‐80%PEO)CH₂COOH and its sodium salt (PE‐b‐80%PEO)CH₂COO^? Na⁺ for the purpose of improving its compatibility and performance as a matrix for composites. These modified copolymers were characterized by FTIR, DSC, and mass spectrometry. The sorption of water of these copolymers and their composites with lithium nitrate was also compared, as well as the electrical properties of their composites were measured by electrical impedance spectroscopy. For the composites obtained with PE‐b‐80%PEO and lithium nitrate, it was found that lithium cation plays an important role increasing the sorption rate, which is maximized for the PE‐b‐80%PEO + (21% lithium nitrate) composite. For the copolymers (PE‐b‐80%PEO)CH₂COOH and (PE‐b‐80%PEO)CH₂COO^? Na⁺ and their composites, the highest sorption rate was observed for salt in the following order: COO^? Na⁺ > COOH > OH. The PE‐b‐80%PEO + (21% lithium nitrate) composite behaves as a solid polymeric ionic conductor fitting the Williams–Landel–Ferry equation. However, both (PE‐b‐80% PEO)CH₂COOH and (PE‐b‐80%PEO)CH₂COO^? Na⁺ + (21% lithium nitrate) composites fitted the Variable Range Hopping equation, indicating a conductance trend with temperature governed by a thermally activated with energy of 0.482 and 0.524 eV and not by a relaxation process. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1809–1817, 2010     

Synthesis and Antimicrobial Evaluation of (1‐(2‐(Benzyloxy)‐2‐oxoethyl)‐1H‐1,2,3‐triazol‐4‐yl)methyl Benzoate Analogues

A convenient one pot synthesis of 20 (1‐(2‐(benzyloxy)‐2‐oxoethyl)‐1H‐1,2,3‐triazol‐4‐yl)methyl benzoate analogues ( 5a – 5t ) with ester functionality was carried out via Cu(I) catalyzed click reaction between prop‐2‐yn‐1‐yl benzoates and benzyl 2‐azidoacetates. The structure of synthesized triazoles were explicated by various spectral techniques like FT‐IR, ¹H NMR, ¹³C NMR, and high‐resolution mass spectrometry and evaluated for in vitro antimicrobial potential against Staphylococcus aureus, Escherichia coli, Klebsiella pneumoniae, Enterobacter aerogenes, Candida albicans, and Aspergillus niger. Most of synthesized triazole derivatives exhibited average to excellent activity against tested microbial strains.     

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 antimicrobial activity of bulky 3,5‐di‐tert‐butyl substituent‐containing silver–N‐heterocyclic carbene complexes

A series of novel benzimidazolium bromides containing bulky 3,5‐di‐tert ‐butyl group were synthesized in high yields as N‐heterocyclic carbene (NHC) ligands. These NHC ligands were metallated with Ag₂O under moderate conditions to give novel silver–NHC complexes. The structures of all compounds were characterized using ¹H NMR, ¹³CNMR, infrared and elemental analysis techniques, which supported the proposed structures. The silver–NHC complexes were screened for their in vitro antimicrobial activities against the standard bacterial strains Enterococcus faecalis , Staphylococcus aureus , Escherichia coli and Pseudomonas aeruginosa and the fungal strains Candida albicans and C. tropicalis . The results showed that most of the silver–NHC complexes inhibited the growth of all bacterial strains and fungal strains and were found to display effective antimicrobial activity against different microorganisms.     

Synthesis and Characterization of Some New Heteroaromatic Compounds Having Chirality Adjacent to a 1,3,4‐Thiadiazole Moiety and Their Antimicrobial Activities

Through a cyclization reaction of 2‐phenylbutyric acid with N‐ phenylthiosemicarbazide and POCl₃, novel 1,3,4‐thiadiazole derivatives were synthesized. Their structures were confirmed using IR, ¹H NMR, and ¹³C NMR spectroscopies and elemental analysis. The antibacterial activities of the obtained 1,3,4‐thiadiazole derivatives were tested against Gram‐negative bacteria (Salmonella enteritidis , Salmonella typhimurium , Enterobacter aerogenes , Salmonella infantis , Salmonella kentucky , and Escherichia coli ) and Gram‐positive bacteria (Staphylococcus aureus , Bacillus subtilis , and Enterococcus durans ) using a disk diffusion method. Moreover, an antifungal activity experiment was performed against Candida albicans using the disk diffusion method. It was observed that the synthesized 1,3,4‐thiadiazole derivatives exhibited effective antimicrobial activity against S. aureus , E. coli , and C. albicans . Based on these results, the 1,3,4‐thiadiazole derivatives can be considered as a source of bioactive agents for pharmacological and medicinal applications.     

Novel antimicrobial polyethylene composites prepared by metallocenic in situ polymerization with TiO2‐based nanoparticles

Polyethylene (PE) composites with titanium oxide (TiO₂) nanoparticles were produced via in situ polymerization representing a novel route to obtain antimicrobial polymeric materials. The TiO₂ nanoparticles synthesized by the sol–gel method were used either as‐synthesized or modified organically with hexadecyltrimethoxysilane (Mod‐TiO₂). These particles were added, together with the catalytic system (formed by a metallocenic catalyst and methylaluminoxane as cocatalyst), directly to the reactor, yielding in situ PE composites with 2 and 8 wt % content of nanofiller. The catalytic polymerization activity presented a slight decrease with the incorporation of the TiO₂ and Mod‐TiO₂ nanoparticles compared to polymerization without filler. Regarding the properties of the composites, crystallinity increased slightly when the different nanofillers were added, and the elastic modulus increased around 15% compared to neat PE. PE/TiO₂ nanocomposites containing 8 wt % of TiO₂ exposed to UVA irradiations presented antimicrobial activity against Escherichia coli. The PE/Mod‐TiO₂ nanocomposite with 8 wt % filler killed 99.99% of E. coli, regardless of light and time irradiation. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Conjugates with an Antimicrobial Effect Based on New Derivatives of Mercaptobenzoxazole Esterified onto Poly(maleic anhydride‐alt‐vinyl acetate)

New compounds with biological activity based on hydroxy‐amino derivatives of benzoxazolyl‐2‐mercaptoformic acid, benzoxazolyl‐2‐mercaptoacetic acid, and chloracetyl‐2‐mercaptobenzoxazole have been synthesized. The chemical bonding of these compounds to poly(maleic anhydride‐alt‐vinyl acetate), through esterification, leads in obtaining conjugates of polymer biologically active compound type, tests indicating a sustained release of the active chemical, with time (between 5 and 6 h). Reaction products were characterized through elemental and spectral analysis (FTIR and ¹H NMR). Toxicology and antimicrobial activity tests recommend compounds with small molecule, as well as their conjugates as therapeutical candidates (antimicrobial inhibitors) for pharmacological application.     

Synthesis,Characterization and Evaluation of Antimicrobial and Antituberculosis Activities of New N‐(Substituted‐thioureido)aminobicyclo Dicarboximide and 3,4‐Disubstituted 1,2,4‐Triazolino‐5‐thione

The novel N‐(substituted‐thioureido)aminobicyclo dicarboximide and 3,4‐disubstituted 1,2,4‐triazolino‐5‐thione were synthesized and their antimicrobial and antituberculosis activities were examined. Selected dicarboxylic acid anhydrides were used to obtain derivatives of thiosemicarbazide and dicarboximide. Dicarboximides were also cyclized in the presence of an alkaline solution giving 1,2,4‐triazolino‐5‐thione. The chemical structure of all compounds was confirmed by IR, ¹H NMR, ¹³C NMR, the X‐ray crystallography ( 6 , 11 ) and elemental analysis. Antimicrobial and antituberculosis activities of the derivatives were measured.     

Design,Regiospecific Green Synthesis,Chemical Computational Analysis,and Antimicrobial Evaluation of Novel Phthalazine Heterocycles

Phthalazines have received considerable attention for their wide antimicrobial activity. Regiospecific nucleophilic attack of 4‐benzylphthalazin‐1‐ol by the 1‐oxo rather than the aza group on different alkyl halides gave novel phthalazine heterocyclic derivatives. Moreover, a variety of nucleosides bonded to electron‐withdrawing groups were synthesized using 4‐benzylphthalazine‐1‐ol. The density functional theory has been used to investigate the electronic structure of the synthesized compounds. All of the synthesized derivatives showed remarkable activity when tested against Gram‐positive and Gram‐negative bacteria, Aspergillus niger, and Candida albicans. The reactivity of these nucleosides was expected to arise from their bonding with the lone pair of N‐atom of the macromolecules of bacteria. These bonding were expected to inhibit the enzyme by forming highly stable complex with lower highest occupied molecular orbital energy. The structures of these synthesized derivatives were established by Fourier transform infrared, ¹H‐NMR, and ¹³C‐NMR spectroscopic evidence.     

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 and Antimicrobial Activity of Some Condensed [4‐(2,4,6‐Trimethylphenyl)‐1(2H)‐oxo‐phthalazin‐2‐yl]acetic Acid Hydrazide

Some new 1,2,4‐triazolo‐, 1,3,4‐oxadiazolo‐, 1,3,4‐thiadiazol‐, and pyrazolo‐2,4,6‐trimethylphenyl‐1(2H)‐oxo‐phthalazine derivatives were synthesized and identified by IR, ¹H NMR, ¹³C NMR, MS and elemental analysis. The new compounds were synthesized with the objective of studying their antimicrobial activity.     

Synthesis and Antimicrobial Activity of Some New N‐substituted‐5‐arylidene‐thiazolidine‐2,4‐diones

A total of 17 new N‐substituted derivatives ( 2b , 2c , 2d , 2e , 2f , 2g , 2h , 2i , 2j , 2k and 3b , 3c , 3d , 3e , 3f , 3g , 3h ) of 5‐((2‐phenylthiazol‐4‐yl)methylene) thiazolidine‐2,4‐dione ( 2a ) and 5‐(2,6‐dichloro‐ benzylidene)thiazolidine‐2,4‐dione ( 3a ) were synthesized. The structural elucidation of the newly synthesized compounds was based on elemental analysis and spectroscopic data (MS, ¹H NMR, ¹³C NMR), and their antimicrobial activities were assessed in vitro against several strains of Gram‐positive and Gram‐negative bacteria and one fungal strain (Candida albicans) as growth inhibition diameter. Some of them showed modest to good antibacterial activity against Gram‐negative Escherichia coli and Salmonella typhimurium and Gram‐positive Staphylococcus aureus, Bacillus cereus, and Enterococcus fecalis bacterial strains, whereas almost all the compounds were inactive against Listeria monocytogenes. All of the synthesized compounds showed moderate to very good activity against C. albicans.     

Synthesis,antimicrobial activity,and molecular docking study of formylnaphthalenyloxymethyl‐triazolyl‐N‐phenylacetamides

In the present study, substituted formylnaphthalenyloxymethyl‐triazolyl‐N‐phenylacetamide derivatives ( 6a – k ) have been designed and synthesized employing click chemistry approach and evaluated for their in vitro antifungal and antibacterial activities. All the newly synthesized compounds were thoroughly characterized by ¹H NMR, ¹³C NMR, and HRMS spectral techniques. Among the screened compounds, 6d , 6e , 6j , and 6k have shown good antifungal and antibacterial activities. Compound 6k has shown very effective antimicrobial activity. We further performed exploratory docking studies on microbial DNA gyrase to rationalize the in vitro biological data and to demonstrate the mechanism of antimicrobial activity. This is the first report to demonstrate the formylnaphthalenyloxymethyl, triazole, and N‐phenylacetamide hybrids as potential antimicrobial agents.     

1,3‐Alternate Tetraamido‐Azacalix[4]arenes as Selective Anion Receptors

Six tetraaza[1.1.1.1]cyclophane derivatives bearing peripheral amide groups were prepared according to two distinct synthetic strategies that depend on the connection pattern between the aryl units. NMR experiments combined with the X‐ray structures of two tetraamide derivatives 4 b and 10 show that these cavitands adopt a 1,3‐alternate conformation both in solution and in the solid state. Consequently, the four amide groups of the aza[1.1.1.1]‐m,m,m,m‐cyclophane isomer 10 can contribute to the same recognition process towards neutral water molecules or anion guests. NMR experiments, mass spectrometry analyses and single‐crystal X‐ray structures confirm the anion‐binding ability of this receptor. Absorption spectrophotometric titrations in nonpolar solvents provided evidence for the selectivity of 10 to chloride anions in the halide series, with a corresponding association constant K_a reaching 2.5×10⁶ m ^?1.     

Synthesis,Dissociation Constants,and Antimicrobial Activity of Novel 2,3‐Disubstituted‐1,3‐thiazolidin‐4‐one Derivatives

In this article, a new series of 2,3‐disubstituted‐1,3‐thiazolidin‐4‐one derivatives have been designed, synthesized, and evaluated as antimicrobial agents. New compounds were prepared by the cyclization reaction of N‐substituted carboxylic acid hydrazide derivatives with mercaptoacetic acid. The structures of the obtained compounds were confirmed by means of IR, ¹H NMR, and ¹³C NMR spectra. The dissociation constants were determined using spectrophotometric method. All synthesized compounds were tested for their in vitro antibacterial and antifungal activities using the broth microdilution method.     

Synthesis,antimicrobial, and antioxidant activities of new pyridyl‐ and thiazolyl‐bearing carbohydrazides

A series of novel substituted (E)‐N′‐benzylidene‐4‐methyl‐2‐(2‐propylpyridin‐4‐yl)thiazole‐5‐carbohydrazide derivatives ( 6a‐l ) have been synthesized by following the multistep synthetic route starting from prothionamide. The resulting compounds were characterized via ¹H, ¹³C NMR, and HRMS spectral data. The synthesized carbohydrazides were evaluated for their in vitro antimicrobial and antioxidant activities. Tested molecules have displayed moderate to good growth inhibition activity. Among the screened compounds, 6b , 6e , 6j, and 6k are found to be the more promising antimicrobial agents. A 2,2‐diphenyl‐1‐picrylhydrazyl assay was used to test the antioxidant activity of the carbohydrazides. The carbohydrazide derivatives 6b and 6i have shown better free‐radical scavenging ability than the other investigated compounds.     

Triumfettosterol Id and Triumfettosaponin,a New (Fatty Acyl)‐Substituted Steroid and a Triterpenoid ‘Dimer’ Bis(β‐D‐glucopyranosyl) Ester from the Leaves of Wild Triumfetta cordifolia A. Rich. (Tiliaceae)

Two new triterpenoid derivatives were isolated from the leaves of wild Triumfetta cordifolia A. Rich . and identified to be a (fatty acyl)‐substituted steroid 1 and a triterpenoid saponin ‘dimer’ 2 , named (3β)‐stigmasta‐5,22‐diene‐3,29‐diol 3‐propanoate 29‐triacontanoate and (2α,3β,19α)‐2,3,19‐trimethoxyurs‐12‐ene‐24,28‐dioic acid 24‐[(2α,3β)‐24,28‐bis(β‐D ‐glucopyranosyloxy)‐2‐hydroxy‐24,28‐dioxours‐12‐en‐3‐yl] ester, respectively. These compounds were obtained together with a mixture of known sterols (stigmasterol/β‐sitosterol=(3β,22E)‐stigmasta‐5,22‐dien‐3‐ol/(3β)‐stigmast‐5‐en‐3‐ol) and trans‐tiliroside ( 3 ). The structures 1 and 2 were determined on the basis of NMR data (¹H‐, ¹³C‐, and 2D‐NMR analyses) and mass spectrometry and confirmed by chemical transformations. The antimicrobial activities of trans‐tiliroside ( 3 ) against eight bacterial and two fungal strains were evaluated. This compound showed weak activities on some bacterial strains.     

Synthesis and in vitro Antimicrobial Activity of Nalidixic Acid Hydrazones

A series of nalidixic acid‐based hydrazones have been synthesized and evaluated for their in vitro antimicrobial activity using the broth microdilution method against a panel of reference strains of microorganisms, including Gram‐positive bacteria, Gram‐negative bacteria, and fungi belonging to yeasts Candida spp. and molds Aspergillus spp., Penicillium spp., and Rhizopus spp. Nalidixic acid derivatives were obtained by condensation reaction of nalidixic acid hydrazide with substituted (hetero)aromatic aldehydes. All compounds have been characterized by ¹H NMR and ¹³C NMR spectra. The antimicrobial activity indicated that compound with indole substituent could be a promising lead for future development of active antifungal agents.