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91.
Maria Teresa Cocco Cenzo Congiu Valentina Onnis 《Journal of heterocyclic chemistry》1995,32(2):463-466
The heterocyclization of 3-aminopropenethioamides 1 and 2 with 2-bromoacetophenone is reported. The p-toluenesulphonic acid catalyzed reaction gives a direct route to 1,4-thiazepines 3 and 5 , while in the presence of triethylamine thiophene 4 and 1,4-thiazepin-5-one 6 are obtained. 相似文献
92.
M Zia-Ul-Haq S Ahmad L Calani T Mazzeo D Del Rio N Pellegrini V De Feo 《Molecules (Basel, Switzerland)》2012,17(9):10306-10321
The present investigation has been carried out to determine the proximate composition, amino acids, metal contents, oil composition as well as the antioxidant capacity of the seeds of Ipomoea hederacea Jacq. and Lepidium sativum L. Proximate composition indicated a great difference in oil (14.09 ± 0.66, 28.03 ± 1.05) and fibre (16.55 ± 0.31, 6.75 ± 1.20) contents for I. hederacea and L. sativum, respectively. Fatty acid profile indicated that oleic acid (19.50 ± 0.37, 30.50 ± 0.16) and linoleic acid (52.09 ± 0.48, 8.60 ± 0.38) are the major fatty acids. γ-Tocopherol and d-tocopherol (28.70 ± 0.14, 111.56 ± 0.37) were the most abundant in the seed oil of I. hederacea and L. sativum, respectively. Results of TEAC, FRAP and TRAP antioxidant assays indicated that L. sativum has much greater antioxidant potential than I. hederacea. 相似文献
93.
Serra S 《Natural product communications》2012,7(4):455-458
The enantioselective synthesis of (S)-1-hydroxy-1,3,5-bisabolatrien-10-one 1 is here described. This sesquiterpene was prepared using (S)-3-(2-methoxy-4-methyl-phenyl)butan-1-ol as a chiral building block. Two different pathways were employed and both turned out to be high yielding, affording 1 in good chemical purity and without any racemization of the existing stereocenter. The spectroscopic data of the synthetic (S)-1 were in very good agreement with those reported for the natural compound, which was extracted from Juniperus formosana heartwood and from the leaves of J. chinensis. The positive sign of the measured optical rotation value of synthetic (S)-1 allows the unambiguous assignment of the absolute configuration of (+)-1 as the (S)-enantiomer. This finding corrects the previous configuration determination which indicated the opposite result. At last, since even (R)-3-(2-methoxy-4-methyl-phenyl)butan-1-ol is preparable in high enantiomer purity by mean of a different biocatalytic process, the formal synthesis of natural (R)-1 was also accomplished. 相似文献
94.
Montalbano F Candeias NR Veiros LF André V Duarte MT Bronze MR Moreira R Gois PM 《Organic letters》2012,14(4):988-991
The dative N-B bond was used to simply assemble heterocycles with a skeleton akin to the 5-oxofuro[2,3-b]furan motif. Twenty-five new N-B heterocycles were prepared via a highly efficient one-pot four-component reaction in yields and diastereoselectivities up to 95% and >97%, respectively. Several reaction intermediates were discovered using electrospray ionization mass spectroscopy which set the basis for the mechanism elucidation using DFT calculations. 相似文献
95.
Single-walled carbon nanotubes (SWCNTs) should constitute an important natural step towards the improvement of the analytical performance of microfluidic electrochemical sensing. SWCNTs inherently offer lower detection potentials, higher surfaces and better stability than the existing carbon electrodes. However, pristine SWCNTs contain some carbonaceous and metallic impurities that influence their electrochemical performance. Thus, an appropriate processing method is important for obtaining high purity SWCNTs for analytical applications. In this work, a set of 0.1 mg mL(-1) SWCNT dispersions with different degrees of purity and different dispersants (SDBS; pluronic F68 and DMF) was carefully characterized by near infrared (NIR) spectroscopy giving a Purity Index (NIR-PI) ranging from 0.039 to 0.310. The highest purity was obtained when air oxidized SWCNTs were dispersed in SDBS, followed by centrifugation. The SWCNT dispersions were utilized to modify microfluidic chip electrodes for the electrochemical sensing of dopamine and catechol. In comparison with non-SWCNT-based electrodes, the sample with the highest NIR-PI (0.310) exhibited the best analytical performance in terms of improved sensitivity (3-folds higher), very good signal-to-noise ratio, high resistance-to-fouling in terms of relative standard deviation (RSD 7%; n = 15), and enhanced resolution (2-folds higher). In addition, very well-defined concentration dependence was also obtained with excellent correlation coefficients (r ≥ 0.990). Likewise, a good analytical sensitivity, suitable detection limits (LODs) and a very good precision with independence of the concentration assayed (RSDs ≤ 5%) was achieved. These valuable features indicate the suitability of this material for quantitative analysis. NIR-PI and further TEM and XRD characterization demonstrated that the analytical response was driven and controlled by the high NIR-PI of the SWCNTs used. The significance of this work is the demonstration for the first time of the sensitivity-purity relationship in SWCNT microfluidic chips. A novel and valuable analytical tool for electrochemical sensing has been developed: SWCNTs with high purity and a rich surface chemistry with functional groups, both essential for analytical purposes. Also, this work helps to better understand the analytical potency of SWCNTs coupled to microfluidic chips and it opens new gates for using these unique dispersions in real-world applications. 相似文献
96.
Godinho V Rojas TC Trasobares S Ferrer FJ Delplancke-Ogletree MP Fernández A 《Microscopy and microanalysis》2012,18(3):568-581
Nanoscale resolution electron microscopy analysis combined with ion beam assisted techniques are presented here, to give answers to full characterization of morphology, growth mode, phase formation, and compositional distribution in nanocomposite TiAlSiN coatings deposited under different energetic conditions. Samples were prepared by magnetron sputtering, and the effects of substrate temperature and bias were investigated. The nanocomposite microstructure was demonstrated by the formation of a face-centered cubic (Ti,Al)N phase, obtained by substitution of Al in the cubic titanium nitride (c-TiN) phase, and an amorphous matrix at the column boundary regions mainly composed of Si, N (and O for the samples with higher oxygen contents). Oxygen impurities, predicted as the principal responsible for the degradation of properties, were identified, particularly in nonbiased samples and confirmed to occupy preferentially nitrogen positions at the column boundaries, being mainly associated to silicon forming oxynitride phases. It has been found that the columnar growth mode is not the most adequate to improve mechanical properties. Only the combination of moderate bias and additional substrate heating was able to reduce the oxygen content and eliminate the columnar microstructure leading to the nanocomposite structure with higher hardness (>30 GPa). 相似文献
97.
Bratsos I Mitri E Ravalico F Zangrando E Gianferrara T Bergamo A Alessio E 《Dalton transactions (Cambridge, England : 2003)》2012,41(24):7358-7371
With the aim of expanding the structure-activity relationship investigation, the series of Ru(II) half sandwich coordination compounds of the type [Ru([9]aneS3)(chel)(L)](n+) previously described by us (where [9]aneS3 is the neutral face-capping ligand 1,4,7-trithiacyclononane, chel is a neutral or anonic chelating ligand, L = Cl(-) or dmso-S, n = 0-2) was extended to 1,4,7-triazacyclononane ([9]aneN3). In addition, new neutral N-N, and anionic N-O and O-O chelating ligands, i.e. dach (trans-1,2-diaminocyclohexane), pic(-) (picolinate), and acac(-) (acetylacetonate), were investigated in combination with both [9]aneS3 and [9]aneN3. Overall, ten new half-sandwich complexes were prepared and fully characterized and their chemical behaviour in aqueous solution was established. The single-crystal X-ray structures of eight of them, including the versatile precursor [Ru([9]aneN3)(dmso-S)(2)Cl]Cl (9), were also determined. The results of in vitro antiproliferative tests performed on selected compounds against MDA-MB-231 human mammary carcinoma cells confirmed that, in this series, only compounds that hydrolyse the monodentate ligand at a reasonable rate show moderate activity, provided that the chelate ligand is a hydrogen bond donor. 相似文献
98.
Grażyna Janowska Teresa Mikołajczyk Dorota Wołowska-Czapnik M. Boguń 《Journal of Thermal Analysis and Calorimetry》2005,82(1):129-135
The paper discusses the thermal properties of alginate fibres made from alginic acid or sodium alginate and from alginates
substituted with divalent metal ions during the fibre-forming stage. Alginate fibres with an addition of silica nanoparticles
have also been examined. The selection of fibre-forming parameters was intended to obtain the best either sorption or strength
properties depending on the specific fibre application. Thermal curves of the fibres under investigations obtained by under
air atmosphere and differential scanning calorimetry (DSC) under neutral gas atmosphere have been interpreted from the view
of physical and chemical changes in the fibre-forming material. Based on thermogravimetric curves, the fibre thermal stability
indices have been determined. It has been found that the addition of silica nanoparticles exerts a positive influence on the
thermal properties of the examined fibres. 相似文献
99.
Oliveira SC Paiva TC Visconti AE Giudici R 《Applied biochemistry and biotechnology》1998,74(3):161-172
Discrimination between different rival models for describing the inhibitory effect of ethanol both on yeast growth and on
fermentation was studied for a continuous process of alcoholic fermentation in a tower reactor with recycling of flocculating
cells. Models tested include linear, parabolic, hyperbolic, exponential, and generalized nonlinear power-law types. The best
expressions were identified under the criteria that all the kinetic parameters should assume acceptable values in a feasible
range and should result in the best fit of the experimental data. The kinetic parameters were estimated from steady-state
data of several sugar concentrations in feeding stream (S0 = 160, 170, 180, 190, 200 g/L), constant dilution rate (D = 0.2 h-1), recycle ratio (α = 13.6), and temperature (T = 30°C). The best model for the yeast growth was of power-law type, whereas
for the product formation the best model was of linear type. These models were able to reproduce the trends of the process
variables satisfactorily. 相似文献
100.
Molins Elies Roig Anna Miravitlles Carlos Moreno-Mañas Marcial Vallribera Adelina Gálvez Nicanor Serra Neus 《Structural chemistry》1998,9(3):203-208
The crystal and molecular structure of (BzlMe3N)
2
+
[Fe2OCl6]2- has been determined. The asymmetric unit contains two benzyltrimethylammonium cations and two half -oxo-bis(trichloro-iron(III)) anions. The bridging -oxygen atoms of these anions are located over crystallographic symmetry elements. Therefore, the two anions resulting from the symmetry operations correspond to two different conformers presenting angular and linear dispositions of the Fe-O-Fe bond angle. Mössbauer spectrum consists of two asymmetric lines that are adequately simulated by two equally populated quadrupole doublets associated with the two iron sites. 相似文献