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41.
Stecko S Jurczak M Urbańczyk-Lipkowska Z Solecka J Chmielewski M 《Carbohydrate research》2008,343(13):2215-2220
The 1,3-dipolar cycloaddition of cyclic nitrone derived from tartaric acid and (S)-5-hydroxymethyl-2(5H)-furanone leads to a single adduct which was transformed into 2,6-dihydroxyhastanecine via reaction sequence involving reduction of the lactone moiety, glycolic cleavage of the terminal diol, and the N-O hydrogenolysis followed by the intramolecular alkylation of the nitrogen atom. 相似文献
42.
A new series of N-acylhydrazone derivatives of 2-mercaptobenzimidazole (2-MBI) has been synthesized through S-alkylation with 1-bromotetradecane and N-alkylation with ethyl-2-chloroacetate. The resulting ester was synthetically modified through hydrazine hydrate to acyl hydrazide which was condensed with aromatic aldehydes to afford the title N-acylhydrazones (4-17). Chemical structures of the newly synthesized compounds have been confirmed through mass, FT-IR and 1HNMR techniques. In vitro free radical scavenging and α-glucosidase inhibition activities of the compounds were investigated with reference to the standard ascorbic acid and acarbose, respectively. Amongst the target compounds, 13 showed the highest inhibition in DPPH scavenging assay (IC50 = 131.50 µM) and α-glucosidase inhibition potential (IC50 = 352 µg/ml). We extended our investigations to explore the mechanism of enzyme inhibition and conducted docking analysis by using Molecular Operating Environment (MOE 2016.08). A homology model for α-glucosidase was constructed and validated using Ramachandran plot. Docking studies were also carried out on human intestinal α-glucosidases. In view of the importance of the nucleus involved, the synthesized compounds might find extensive medicinal applications as reported in the literature. 相似文献
43.
Isatin base Schiff bases (1–20) were synthesized, characterized by 1H NMR and EI/MS and evaluated for α-glucosidase inhibitory potential. Out of these twenty (20) compounds only six analogs showed potent α-glucosidase inhibitory potential with IC50 value ranging in between 2.2 ± 0.25 and 83.5 ± 1.0 μM when compared with the standard acarbose (IC50 = 840 ± 1.73 μM). Among the series compound 2 having IC50 value (18.3 ± 0.56 μM), 9 (83.5 ± 1.0 μM), 11 (3.3 ± 0.25 μM), 12 (2.2 ± 0.25 μM), 14 (11.8 ± 0.15 μM), and 20 (3.0 ± 0.15 μM) showed excellent inhibitory potential many fold better than the standard acarbose. The binding interactions of these active analogs were confirmed through molecular docking. 相似文献
44.
《Free radical research》2013,47(4-6):285-288
The sulfite radical anion (SO3?) is the first intermediate in the autoxidation of sulfite to sulfate. Using competition kinetics, its reactivities with the nucleic acid bases and the corresponding nucleosides were investigated. The second order rate constants were found to be rather low, k < 1 × 106dm3mol?1s?1 at pH 7. As a competitor, the carotenoid crocin was used, which was found to be bleached very efficiently by SO3? (k = 1.0 × 109dm3mol?1S?1). 相似文献
45.
《Nucleosides, nucleotides & nucleic acids》2013,32(5-8):1549-1552
Abstract Structural and synthetic model are given for (modified) parallel DNAs with non-Watson and Crick duplex formation. 相似文献
46.
Some new Schiff bases (H1-H7) have been synthesized by the condensation of 2-aminophenol, 2-amino-4-nitrophenol, 2-amino-4-methylphenol, 2-amino benzimidazole with thiophene-2-carboxaldehyde and pyrrole-2-carboxaldehyde. The structures of newly synthesized compounds were characterized by elemental analysis, FT-IR, 1 H NMR, UV–VIS, and single crystal X-ray crystallography. The in vitro antibacterial activity of the synthesized compounds has been tested against Salmonella typhi, Bacillus coagulans, Bacillus pumills, Escherichia coli, Bacillus circulans, Pseudomonas, Clostridium and Klebsilla pneumonia by disk diffusion method. The quantitative antimicrobial activity of the test compounds was evaluated using Resazurin based Microtiter Dilution Assay. Ampicillin was used as standard antibiotics. Schiff bases individually exhibited varying degrees of inhibitory effects on the growth of the tested bacterial species. The antioxidant activity of the synthesized compounds was determined by the 1,1-diphenyl-2-picrylhydrazyl(DPPH) method. IC50 value of synthesized Schiff bases were calculated and compared with standard BHA. 相似文献
47.
Malai Haniti S.A. Hamid Aminul Huq Mirza Boujemaa Moubaraki 《Inorganica chimica acta》2009,362(10):3648-41
New copper(II) complexes of general empirical formula, [Cu(NNS)X] (NNS = anionic forms of the 2-acetylpyrazine Schiff bases of S-methyl- and S-benzyldithiocarbazate, Hapsme and Hapsbz) and X = Cl−, Br−, NCS− and NO3− have been synthesized and characterized. X-ray crystal structures of the free ligand, Hapsbz and the complexes, [Cu(apsbz)(NO3)]∞, [Cu(apsme)(NCS)]2 and [Cu(apsme)Cl]2 have been determined. In the solid state, the Schiff base, Hapsbz remains in its thione tautomeric form with the thione sulfur atom trans to the azomethine nitrogen atom. X-ray diffraction shows that the [Cu(apsbz)(NO3)]∞ complex is a novel coordination polymer in which one of the nitrogen atoms of the pyrazine ring bridges two adjacent copper(II) ions. The Schiff base is coordinated to the copper(II) ion in its iminothiolate form via the thiolate sulfur atom, the azomethine nitrogen atom and one of the pyrazine nitrogen atoms, the overall geometry of each copper atom in the polymer being close to a square-pyramid. The complexes, [Cu(apsme)X]2 (X = NCS−, Cl−) are dimers in which each copper atom adopts a five-coordinate near square-pyramidal geometry with an N3S2 coordination environment. The Schiff base coordinates as a uninegatively charged tridentate ligand chelating via the pyridine and azomethine nitrogen atoms and the thiolate sulfur atoms. A nitrogen atom of a unidentate thiocayanate or chloride ligand and a bridging sulfur atom from a second ligand completes the coordination sphere. Room temperature μeff values for the complexes in the solid state are in the range 1.70-2.0 μB typical of uncoupled or weakly coupled Cu(II) centres. Variable temperature susceptibility studies show that the chain complex displays weak ferromagnetic coupling across the pyrazine bridges, while the S-bridged dinuclear compounds display either weak ferromagnetic or weak antiferromagnetic coupling that relates to subtle bridging geometry differences. EPR studies of frozen DMF solutions give rather similar g and ACu values for all compounds indicative of Cu(dx2-y2) ground state orbitals on the Cu centers. 相似文献
48.
The tetragonal-pyramidal VO2+ complexes [VO{(RSC-S)N-NX}2] (1-6) were synthesised by the reactions of VO(OCHMe2)3 with the dithiocarbazate ligands RSC(S)-NH-NX, where X = cyclo-pentyl, cyclo-hexyl or 4-Me2N-C6H4-CH, and R = CH3 or CH2C6H5. The compounds were characterised by elemental analysis, IR- and mass spectrometries, and in cases of compounds 1, 3, 4 and 5, by X-ray diffraction. The chiral compound 4 (X = cyclo-hexyl, R = CH2C6H5) crystallises in the C configuration. In compound 5, the VO moiety is disordered (83.3:16.7%) with respect to the plane spanned by the four equatorial ligand functions. 相似文献
49.
Debora Barros Barbosa Douglas Roberto Monteiro Valentim Adelino Ricardo Barão Ana Carolina Pero Marco Antonio Compagnoni 《Gerodontology》2009,26(3):225-231
Background: The fracture between acrylic denture base material and artificial teeth is a common clinical occurrence in dental prosthodontic practice. Objective: To evaluate the bond strength between acrylic resins and resin denture teeth when submitted by two protocols of monomer liquid application on the tooth surface and using different polymerisation methods. Material and methods: Microwave‐polymerised (Onda‐Cryl), heat‐polymerised (Clássico) and autopolymerising (Jet) acrylic resins and a brand of resin denture teeth (Biotone) were used. The acrylic resins were polymerised according to the cycles: (A) microwave – fast cycle, Onda‐Cryl; (B) microwave – long cycle, Onda‐Cryl; (C) microwave – manufacturer’s cycle, Onda‐Cryl; (T) water bath – long cycle, Clássico and (Q) bench polymerisation cycle, Jet. Thirty specimens were prepared for each polymerisation method; 10 were packed with acrylic resin after 60 s of monomer liquid application on the tooth surface, 10 after 180 s and 10 without any monomer liquid application. For the purpose of the study, a shear test was used. anova and Tukey tests were performed to identify significant differences (α = 0.05). Results: The highest bond strength values were found for monomer surface treatments, regardless of the polymerisation cycles. The highest significant values were found for cycles B (15.4 ± 1.8 MPa), C (11.9 ± 4.9 MPa) and T (15.4 ± 2.6 MPa) for non‐treated and 60 s methylmethacrylate treated groups. Comparing the monomer liquid treatment, they did not differ significantly (p > 0.05), except for cycle A (p < 0.05). Conclusion: Chemical treatment using monomer on the tooth surface prior to the acrylic resin packing improved the bond strength between resin denture tooth and acrylic resin, regardless of monomer liquid treatment protocols. The microwavable resin, polymerised by fast cycle and autopolymerising resin should be avoided for processing denture and denture repairs, respectively. 相似文献
50.
N. R. Kildeeva P. A. Perminov L. V. Vladimirov V. V. Novikov S. N. Mikhailov 《Russian Journal of Bioorganic Chemistry》2009,35(3):360-369
The regularities of the reaction of aminopolysaccharide chitosan with glutaraldehyde (GA) have been considered. The equilibrium forms of GA in water have been thoroughly studied by NMR spectroscopy. It has been established that at pH 5.6, the exchange of the protons of O=CHCH2 groups for deuterium occurs, indicating the presence of an anion, a product of the first stage of the aldol reaction; at pH > 7.2, the formation of the products of an aldol reaction and aldol condensation takes place. The kinetics of the reaction between the amino groups of chitosan and GA, the kinetics of gel formation in chitosan solutions in the presence of GA, and the kinetics of changes in the rigidity of gels formed have been studied by UV spectroscopy. IR spectra of cross-linked chitosan have been obtained. It has been shown that chitosan catalyzes the polymerization of GA to form irregular products; in this process, the length of oligomeric chains in modified or cross-linked chitosan and the concentration of conjugated bonds increase with the GA concentration and pH of the reaction medium. 相似文献