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201.
202.
Djalma Menezes de Oliveira Grácia D. de F. Silva Lucienir P. Duarte Sidney A. Vieira Filho Luciana Guimarães Hélio A. Duarte Edward de Souza 《Structural chemistry》2009,20(6):1005-1011
The complete chemical shift assignments of 3β,16β-dihydroxyfriedelane, a natural compound isolated from the hexane extract
of Maytenus acanthophylla leaves was achieved through 1D/2D NMR spectral data. Combining ab initio Hartree-Fock [HF/6-31G(d)] and Density Functional
Theory [DFT/B3LYP/6-31G(d,p)] calculations with NMR spectral data, it was possible to establish the predominance of the chair-chair-chair-boat-boat
conformation for the five six-membered ring systems in this pentacyclic triterpene. 相似文献
203.
A. Sandrucci R. Lezé G. Guglielmo Bermbach und Sidney S. Emery 《Fresenius' Journal of Analytical Chemistry》1901,40(3):170-172
Ohne Zusammenfassung 相似文献
204.
Ohne Zusammenfassung 相似文献
205.
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207.
Fernando Antonio Simas Vaz Arthur Damásio Moutinho Jose Paulo Rodrigues Furtado de Mendonça Ricardo Tavares de Araújo Sidney José Lima Ribeiro Ferminio César Polachini Younes Messaddeq Marcone Augusto Leal de Oliveira 《Microchemical Journal》2012
The preparation of photo-polymerized sol–gel monolithic stationary phases (MSP) within 100 μm internal diameter polyacrylate-coated fused-silica capillaries for use in capillary electrochromatography (CEC) was optimized. Eight mixtures containing different amounts of methacryloxypropyltrimethoxysilane (MPTMS) as the polymeric precursor, hydrochloric acid solution as the catalyst, toluene as the porogen and bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide (Irgacure 819) as the photo-initiator were irradiated at 370 nm inside the capillaries in order to complete the MSP polymerization, according to a fractional factorial experimental design 2IV4-1. All the preparation procedure, from capillary pretreatment until the MSP is ready to use in CEC, were made in less than four hours in mild conditions. A high pressurization injection device (HPID) useful for micro-volume syringes was built in order to achieve practical, controlled and precise injections of sols, solvents and electrolytes in the capillaries. The eight MSP were equally washed, conditioned and submitted to CEC procedures via short-end injection, which showed higher efficiency and peak height taking shorter analysis time. Electrochromatographic behaviors of the MSP were corroborated with morphological characterizations by scanning electron microscopy. The optimum condition, which allowed the separation of standard mixture containing thiourea (marker compound), naphthalene, acenaphthene, fluorene, phenanthrene and anthracene in twelve minutes without external pressure assistance, showed efficiencies up to 51,460 N/m, relative standard deviation from 0.05 to 3.3% for migration/retention time and from 0.14 to 1.6% for relative area (considering thiourea as an internal standard) and also showed no statistical evidence that three MSP prepared at the same condition are different within 95% confidence interval. 相似文献
208.
Subas M. Sakya Andrew C. Flick Jotham W. Coe David L. Gray Sidney Liang Fabiola Ferri Michel Van Den Berg Kees Pouwer 《Tetrahedron letters》2012,53(7):723-725
Two syntheses of versatile intermediate azepinones 2 and 3 are described. A 6-step intramolecular Dieckmann cyclization and decarboxylation led to the intermediate 3 while an alternate 4-step synthesis of 2 was developed and used for scale-up. The highlight of the second synthesis is the one-step per-bromination/elimination protocol from readily available azepinone 13a to provide a versatile scaffold in vinyl bromide 5, which enables SAR around the aryl moiety. An example of the elaboration of the intermediate 2 toward a heteroaryl azepinone is also described. 相似文献
209.
Marcelo Nalin Sidney Jos Lima Ribeiro Youns Messaddeq Jos Schneider Pedro Donoso 《Comptes Rendus Chimie》2002,5(12)
A systematic investigation on glass formation in the ternary system InF3–BaF2–Sc(PO3)3n has been carried out. Scandium polyphosphate Sc(PO3)3n has been used as a third component in order to investigate the possibilities of obtaining new stable glasses. The above long-chain polyphosphate has been prepared using a specially elaborated cryo-technique, which allowed the preparation of high-purity product. Stable ternary compositions have been obtained within the compositions range (in mol%): 5–75 InF3, 0–80% BaF2, 0–50% Sc(PO3)3n. Glasses were characterized by Differential Scanning Calorimetry, vibrational spectroscopy (Raman) and 31P NMR. Structural features for the glass were put forward. Isolated P(O,F)4 groups or fluoroindated metaphosphate units could be identified depending on glass compositions. 相似文献
210.
The first complete, systematic study of DNA degradation by bleomycin under conditions analogous to those likely in a therapeutic setting has been carried out. Hairpin DNAs selected for their ability to bind strongly to BLM A(5) were used to determine the relationship between high-affinity DNA binding sites and the cleavage efficiency and selectivity of BLM A(5) and deglycoBLM A(5) on these DNAs. Of the 10 hairpin DNAs examined, 8 contained at least one 5'-GC-3' or 5'-GT-3' cleavage site, which have traditionally been associated with strong cleavage by Fe·BLM. In the hairpin DNAs, these included the strongest cleavage sites for BLM A(5) and were generally among those for deglycoBLM A(5). However, numerous additional cleavages were noted, many at sequences not usually associated with (deglyco)BLM-mediated cleavage. The remaining DNAs lacked the preferred (5'-GC-3' or 5'-GT-3') BLM cleavage sequences; however, strong cleavage was nonetheless observed at a number of unusual cleavage sites. The most prominent cleavage sequences were 5'-AT-3', 5'-AA-3', 5'-GA-3', and 5'-TT-3'; treatment with Fe(II)·BLM A(5) or Fe(II)·deglycoBLM A(5) resulted in strong cleavage at these sequences. Additionally, in contrast with BLM A(5), which produced cleavage within the randomized and flanking invariant regions, deglycoBLM A(5) showed a preference for cleavage in the randomized region of the DNAs. Previous reports have established that deglycoBLM exhibits decreased DNA cleavage efficiency relative to BLM. This was also generally observed when comparing cleavage efficiencies for the strongly bound hairpin DNAs. However, some cleavage bands produced by Fe·deglycoBLM A(5) were stronger in intensity than those produced by BLM A(5) at concentrations optimal for both compounds. To investigate the chemistry of DNA degradation, selected hairpin DNAs were treated with n-butylamine following cleavage with Fe(II)·BLM A(5) or Fe(II)·deglycoBLM A(5) to explore the alkali labile pathway of DNA degradation by BLM. While all 10 DNAs showed evidence of alkali labile products, five DNA hairpins afforded some products formed solely via the alkali labile pathway. 相似文献