Synthesis of D-Ala--D-Ala analogues with postulated antibacterial activity

The syntheses of the L,L- and D,D-stereoisomers of N-phenoxyacetyl-X-alanine in which X=His, Tyr, or Lys, are described. The antibacterial activity of some of the peptide derivatives and their synthetic intermediates have been examined. Some of the intermediates exhibited moderate activity against viridans streptococci, enterococci and Streptococcus agalactiae. None of the compounds were active against beta-lactamase producing bacteria or served as beta-lactamase inhibitors.     

Synthesis, spectral studies and antibacterial activity of novel macrocyclic Co(II) compounds

Ten novel macrocyclic Co(II) compounds have been synthesized by treating four N(4) and six N(2)O(2) donor macrocycles with cobalt chloride in methanol. These compounds were characterized by elemental, IR, (1)H, (13)C NMR, mass, electronic spectral analysis, molar conductance and magnetic susceptibility measurements. Thermal behavior of these compounds has been studied by the thermogravimetric analysis. An octahedral geometry has been proposed for all of these complexes. All the macrocycles and macrocyclic Co(II) compounds along with existing antibacterial drugs were screened for antibacterial activity against Gram +ve and Gram -ve bacteria. All these compounds were found to be more active when compared to streptomycin and ampicillin.     

Synthesis,characterization, antibacterial studies and quantum-chemical investigation of the new fluorescent Cr(III) complexes

Coordination of the ligands derived from benzimidazole with Cr(III) led to the formation of new fluorescent Cr (III) complexes. The structures of the new complexes were established by spectral, analytical data and Job’s method and an octahedral geometry was proposed for the complexes. Also, the DFT methods were employed to gain a deeper insight into geometry and spectral properties of the new Cr (III) complexes. The DFT-calculated vibrational modes of Cr(III) complexes are in good agreement with the experimental values, confirming suitability of the optimized geometries for the complexes. Fluorescent ligands and chromium complexes were spectrally characterized by UV–Vis and fluorescence spectroscopy. Results revealed that Cr(III) complexes generate fluorescence in dilute solution of DMSO. Calculated electronic absorption spectra were also provided by time-dependent density functional theory (TD-DFT) method. The new complexes exhibited potent antibacterial activity against a panel of strains of Gram negative bacterial and Gram positive species and their MIC was also determined. Two strains of Gram positive and two strains of Gram negative bacteria.     

Synthesis and photophysical,antibacterial studies of some novel molecular tweezers

Zeroth and first generation dendritic wedges with thiophene amide as surface group and 1, 2, 3-triazole as bridging unit which can function as molecular tweezers are synthesised by both convergent and divergent approaches. All the synthesised dendritic wedges displayed the absorbance band between 256 and 294 nm and fluorescence maximum between 357 and 528 nm supporting their self complementary property. Dendritic wedge 5 showed better antibacterial activity than other dendritic wedges in the assay against the human pathogens viz Staphylococcus aureus, Escherichia coli, Bacillus cereus and Klebsiella pneumonia and the dentritic wedge 5 was also effective in the computational molecular docking studies.     

Synthesis and antibacterial activity of some novel triazolothienopyrimidines

A novel series of some novel 5-substituted-1,2,4-triazolo[4,3-c]8,9,10-trihydrocyclopenta/8,9,10,11,12-pentahydrocyclohepta[b]thieno[3,2-e]pyrimidin-3-thiones has been synthesized. The intermediates 4-chloro-2-substituted-5,6,7-trihydrocyclopenta/5,6,7,8,9-pentahydrocyclohepta[b]thieno[2,3-d]pyrimidines were prepared by warming 2-substituted-5,6,7-trihydrocyclopenta/5,6,7,8,9-pentahydrocyclohepta[b]thieno[2,3-d]pyrimidin-4[3H]-ones with oxalyl chloride. Thieno[2,3-d]pyrimidin-4[3H]-ones were prepared by a novel, microwave assisted, solvent free, synthetic route under basic conditions hitherto unreported in the literature from ortho amino ester of thiophene. The chloro derivatives, without further purification, were hydrazinated to yield 2-substituted-4-hydrazino-5,6,7-trihydrocyclopenta/5,6,7,8,9-pentahydrocyclohepta[b]thieno[2,3-d]pyrimidines. These compounds were cyclized with carbon disulphide to give the title compounds in quantitative yields. The final compounds were screened for antibacterial activity by Kirby Bauer's method using ampicillin as the standard against various gram positive and gram negative bacteria. All the compounds showed antibacterial activity comparable with the standard.     

Synthesis and cytotoxic activity of novel curcumin analogues

Five novel curcumin analogues bearing different substituents at 4-position of phenyl group were synthesized. Their structures were confirmed by NMR and HRMS spectrum. Their cytotoxic activities against six tumor cell lines were tested by the standard MTT assay in vitro. The results indicated that four analogues （1A-1C, 1E） with solubilizing moieties showed selective potent cytotoxicity against HepG2, HeLa and CT26 cell lines, and analogue 1A and 1C exhibited more potent cytotoxicity than curcumin against CT26 cell line. It was suggested that introduction of appropriate substituents to 4-position of phenyl group might be a potential option for structural modification of curcumin.     

Synthesis and studies of antibacterial activity of pongaglabol

Pongaglabol [8-hydroxy-5-phenyl-furo[2,3-h]benzo(b)pyran-7-one] was synthesized and tested for antibacterial effects againstShigella dysenteriae, Salmonella typhi, Streptococcus β-haemolyticus andStaphylococcus aureus. The synthesized compounds were characterized using UV, IR and¹H NMR spectral data     

Synthesis and antitumor activity of novel salvicine analogues

Systematic structure modification of the side train of the lead compound saprothoquinone provides a series of salvicine analogues,fifteen of them were first reported.Some compounds were demonstrated potent cytotoxicity against tumor cells with the 50%inhibition concentration in the micromolar range.Furthermore some compounds showed potent topoisomeraseⅡinhibitory effects.The preliminary structure-activity relationship of saprorthoquinone analogues was discussed according to their cytotoxicity against thr...     

Synthesis,antibacterial activity and docking studies of substituted quinolone thiosemicarbazones

Abstract

Fifteen 2-quinolone thiosemicarbazone derivatives of which eleven were new, were synthesized at room temperature. The key intermediate was the quinolone carbaldehyde, from which thiosemicarbazones were formed by the reaction of thiosemicarbazides with the aldehyde moiety. The structures of the synthesized compounds were elucidated by 1D and 2D-NMR spectroscopy and mass spectrometry. The synthesized compounds showed antibacterial activity with MBCs in the range 0.80 to 36.49?mM against Staphylococcus aureus, Staphylococcus aureus Rosenbach (MRSA), Pseudomonas aeruginosa, Klebsiella pneumoniae, Escherichia coli and Salmonella typhimurium. The best activity was seen when a larger halogen such as chlorine and bromine were substituted at C-6 on the quinolone scaffold and when a planar phenyl group was present on the thiosemicarbazone moiety. Activity was reduced when a smaller fluorine atom was present at C-6 or when a methyl group was attached to the thiosemicarbazone. This group of compounds showed a high negative binding affinity, which suggested promising antimcrobial activity. The 6-chloro derivative with a phenyl group on the thiosemicarbazone had the greatest negative binding affinity.     

Synthesis of caprazamycin analogues and their structure--activity relationship for antibacterial activity

Synthesis of palmitoyl caprazol 7, which possesses a simple fatty acyl side chain at the 3' '-position of the diazepanone moiety, was carried out and their antibacterial activity was evaluated. The key elements of our approach include the improved synthesis of the key 5'-beta-O-aminoribosyl-glycyluridine derivative, installation of the palmitoyl side chain to the cyclization precursor, and the construction of the diazepanone by an intramolecular reductive amination. The second generation synthesis of (+)-caprazol was also established. Palmitoyl caprazol 7 exhibited antibacterial activity against Mycobacterium smegmatis ATCC607 (MIC = 6.25 microg/mL) with potency similar to that of the caprazamycins (CPZs). Palmitoyl caprazol 7 and N6'-desmethyl palmitoyl caprazol 28 also exhibited antibacterial activity against drug-resistant bacteria including methyciline-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Enterococcus (VRE) strains (MIC = 3.13-12.5 microg/mL).     

Synthesis, antibacterial and antifungal activity of some derivatives of 2-phenyl-chromen-4-one

Some derivatives of 2-phenyl-chromen-4-one (flavone ring) have been synthesized and tested for antibacterial and antifungal activities along with their chalcone precursors against four human pathogenic bacteria and five plant mould fungi. The structures of the synthesized compounds were elucidated by UV, IR and¹H NMR spectroscopic techniques, and elemental analysis. The antibacterial and antifungal screens of the synthesized compounds were performed in vitro by the filter paper disc diffusion method and the poisoned food technique.     

Synthesis,structural characterization,biological activity,and theoretical studies of some novel thioether-bridged 2,6-disubstituted imidazothiadiazole analogues

In this study, thioether-bridged imidazo[2,1-b][1,3,4]thiadiazole derivatives that contained both imidazole and 1,3,4-thiadiazole (compounds 7a-7i and 8a-8i ) were synthesized from the reactions of 2-amino-1,3,4-thiadiazole with phenacyl bromide ( 6a - 6i ) (at yields of 59% to 74%). The structure of the synthesized compounds was characterized using ¹H NMR, ¹³C NMR, Fourier-transform infrared spectroscopy, elemental analysis, mass spectroscopy, and X-ray diffraction analysis. Mycelial growth, mycelial growth inhibition, minimum inhibitory concentration, minimum fungicidal concentration, and lethal dose values against various plant pathogenic fungi were determined for all of the target compounds synthesized in the study. The test results showed that most of the compounds had moderate to good antifungal activity. In addition, the absorption, distribution, metabolism, excretion (ADME) parameters of the compounds were calculated, and it was observed that all of the compounds met the drug-likeness rules in general. Finally, using docking simulations, it was found that compounds 7h , 7i , 8h , and 8i showed high affinity to PDB ID:5TZ1, which is an CYP51 antifungal target structure.     

Synthesis and antibacterial activity of some novel pyrazolopyridine derivatives

Eight pyrazolo[3,4-b]pyridine derivatives have been synthesized by Friedl?nder condensation of 5-aminopyrazole-4-carbaldehyde with active methylene compounds in basic medium. These compounds have been screened for their antibacterial activity against two Gram-negative and two Gram-positive bacterium. Pyrazolopyridines having the carboxamide group at the 5-position showed moderate to good activity against P. aeruginosa, E. coli, S. pneumoniae, and B. cereus.     

Synthesis and fungicidal activity of novel strobilurin analogues containing substituted N-phenylpyrimidin-2-amines

A number of novel strobilurin analogues containing substituted N-phenylpyrimidin-2-amines were synthesized.The structures of these new compounds were confirmed by ~1H NMR,IR and elemental analysis.Biological evaluation in the greenhouse showed several compounds have good fungicidal activities at 25 mg/L.     

Synthesis,antibacterial and antitubercular activity of novel Schiff bases of 2-(1-benzofuran-2-yl)quinoline-4-carboxylic acid derivatives

Russian Journal of General Chemistry - Novel Schiff bases of 2-(1-benzofuran-2-yl)quinoline-4-carboxylic acid derivatives 5a–5e were synthesized by the reaction of...     

Synthesis and antibacterial activity of novel 10, 11-epoxy acylide erythromycin derivatives

A series of novel acylide derivatives have been synthesized from clarithromycin A via a facile procedure. The C-3 modifications involved replacing the natural C-3 cladinosyl group in clarithromycin core with different aryl-piperzine sidechain via chemical synthesis. Meanwhile a distinctive intermediate with 10,11-epoxy moiety was obtained. The structure and stereochemistry of this novel structure were confirmed via NMR and X-ray crystallography. Potential anti-bacterial activities against both Grampositive and Gram-negative bacteria were reported. Because of existence of C10,11-epoxide, these derivatives can be used as intermediates for further structural modification.     

Synthesis and antifungal activity of novel 14-membered benzomacrolides, as galbonolide analogues

Asymmetric total synthesis of benzene analogues of galbonolide, a 14-membered antifungal macrolide, possessing a benzene ring instead of a conjugated diene structure, was achieved starting from chiral 1-aryl-1-propanol obtained by enzyme-catalyzed kinetic resolution with high enantioselectivity. Representatively, a method for the introduction of a methylthio and chloride function at the vinyl position was also established. The resulting analogues unfortunately exhibited very little antifungal potency in comparison with galbonolide A.     

Synthesis,complexation and antifungal,antibacterial activity studies of a new macrocyclic schiff base

A new macrocyclic ligand, L was synthesized using the high dilution condition with condensation of triethylene glycol diamine and terephtalaldehyde in ethanol. The obtained product, L was identified by FT‐IR, ¹H‐NMR, ¹³C‐NMR and Mass spectroscopy. The extraction equilibrium constants were estimated using dichloromethane/water membranes transfer with ICP‐AES and AES spectroscopy. Biological studies of this compound was determinated with disc diffusion method. The biological activity results showed that the synthesized ligand L has high activity against the studied microorganisms and high complexation ability against the Fe²⁺ cation.     

Synthesis and antibacterial activity of novel titanium dioxide doped with silver

Pure and silver doped nanoparticles of titanium dioxide (TiO₂) was prepared using novel, modified sol–gel method. The samples were characterized by transmission electron microscopy, X-ray diffraction, N₂ adsorption measurement, atomic absorption spectroscopy (AAS), UV–vis spectroscopy (UV–vis). The antibacterial activity of the prepared samples was indicated by minimal inhibitory concentrations (MIC) and minimal bactericidal concentrations (MBC) values according to the reference methods of Clinical and Laboratory Standards Institute for the determination of MIC of aerobic bacteria by broth microdilution. The results showed very good antibacterial activity of silver nanoforms to bacteria strains: Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli and Klebsiella pneumoniae. The sensitivity of the tested bacteria to silver nanoforms depends on the crystalline form of the carrier—TiO₂, its surface area, porosity, the content of silver, its particle size and oxidation state. The originality of this work is the synthesis of novel type of nanocomposites TiO₂ doped with silver and determination its excellent antibacterial activity.