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101.
[reaction: see text]. The phenylglycinol-derived 2-pyridone 1 undergoes m-CPBA oxidation steroselectively leading to the chiral nonracemic unsaturated bicyclic hydroxylactam 2, from which the enantioselective synthesis of (3R,5R)-3,4,5-trihydroxypiperidine (16) and the formal synthesis of the azasugar epiisofagomine are described. The enantioselective synthesis of (S)-N-Boc-3-hydroxypiperidine and (3R,4S)-3,4-dihydroxypiperidine is also reported. 相似文献
102.
Robert D Amat L Carbó-Dorca R 《Journal of chemical information and computer sciences》1999,39(2):333-344
103.
The reaction rate studies on the hydrolytic cleavage of acetyl salicylate ion (AS-) within the [-OH] range 0.010-0.025 M reveal AS- and -OH as the reactants. The effects of micelles of sodium dodecyl sulfate (SDS) on observed pseudo-first-order rate constants (kobs) for the hydrolytic cleavage of AS- have been studied at different [OH-]. At a constant [OH-], the rate constants (kobs) follow an empirical relationship: kobs = C + F [SDS]T where [SDS]T represents total SDS concentration. The magnitudes of C and F increase with an increase in [OH-]. These data are explained in terms of the pseudophase model of the micelle. 相似文献
104.
Amat M Bosch J Hidalgo J Cantó M Pérez M Llor N Molins E Miravitlles C Orozco M Luque J 《The Journal of organic chemistry》2000,65(10):3074-3084
Reaction of (R)-phenylglycinol with methyl 5-oxopentanoate gave either bicyclic lactam cis-1 (the kinetic product) or its isomer trans-1 (under equilibrating conditions) as the major products, which were converted to the corresponding (cis or trans) unsaturated lactams 4 and 5. On treatment with lithium alkyl (or aryl) cyanocuprates, these chiral building blocks undergo conjugate addition to give enantiopure trans-3,4-substituted 2-piperidone derivatives in high yield and stereoselectivity. The synthetic potential of this transformation is illustrated by the synthesis of (+)-femoxetine and the two enantiomers of the known antidepressant paroxetine. 相似文献
105.
This paper is devoted to the compression of colour images using a new nonlinear cell-average multiresolution scheme. The aim is to obtain similar compression properties as linear multiresolution schemes but eliminating the classical Gibbs phenomenon of this type of reconstructions near the edges. The algorithm is based on a nonlinear reconstruction operator (using a nonlinear trigonometric mean). The new reconstruction is third-order accurate in smooth regions and adapted to the presence of discontinuities. The data used are always centred with optimal support. Some theoretical properties of this scheme are analysed (order of approximation, convergence, elimination of Gibbs effect and stability). 相似文献
106.
Moosa Sadeghi Kiakhani Kamaladin Gharanjig Mokhtar Arami Javad Mokhtari Niyaz Mohammad Mahmoodi 《中国化学会会志》2008,55(6):1300-1307
A group of novel monoazo disperse dyes containing carboxylic acid‐1,8‐naphthalimide group has been synthesized. All intermediates and dyes were purified by recrystalization and the column chromatography method. The purified products were characterized by 1H NMR, 13C NMR, FTIR, DSC, UV‐VIS and Elemental Analysis. Spectrophotometric investigations of the synthesized dyes in different solvents were carried out in order to obtain their absorption maxima, molar extinction coefficients and solvatochromic effects. The absorption maxima of the synthesized dyes in acetone varied (513‐549 nm) and the molar extinction coefficient was (17405‐38939 l/mol cm). By changing the media from chloroform to DMF, the solvatochromism effect for all dyes increased. Dispersion of the synthesized dyes was prepared in water containing dispersing agent and applied to polyester fabrics. The dyed fabrics showed that all of the synthesized dyes were suitable for coloring polyester fibers, producing deep red to bluish red with very good fastness properties. 相似文献
107.
Amat Sergio Levin David Ruiz-Álvarez Juan Trillo Juan C. Yáñez Dionisio F. 《Numerical Algorithms》2022,91(1):51-79
Numerical Algorithms - In many applications, it is useful to use piecewise polynomials that satisfy certain regularity conditions at the joint points. Cubic spline functions emerge as good... 相似文献
108.
109.
Nihan Yayik Maria Prez Elies Molins Joan Bosch Mercedes Amat 《Molecules (Basel, Switzerland)》2021,26(2)
A synthetic route for the enantioselective construction of the tetracyclic spiro[indolizidine-1,3′-oxindole] framework present in a large number of oxindole alkaloids, with a cis H-3/H-15 stereochemistry, a functionalized two-carbon substituent at C-15, and an E-ethylidene substituent at C-20, is reported. The key steps of the synthesis are the generation of the tetracyclic spirooxindole ring system by stereoselective spirocyclization from a tryptophanol-derived oxazolopiperidone lactam, the removal of the hydroxymethyl group, and the stereoselective introduction of the E-ethylidene substituent by acetylation at the α-position of the lactam carbonyl, followed by hydride reduction and elimination. Following this route, the 21-oxo derivative of the enantiomer of the alkaloid 7(S)-geissoschizol oxindole has been prepared. 相似文献
110.
Gemma M. Rodriguez‐Muñiz Juan Gomis Antonio Arques Ana M. Amat M. Luisa Marin Miguel A. Miranda 《Photochemistry and photobiology》2014,90(6):1467-1469
In this work, a kinetic model, in combination with time‐resolved experiments, is applied to assess the involvement of ·OH in the photodegradation of emerging pollutants (EPs) by means of advanced oxidation processes. In contrast with the general assumption, quenching of the short‐lived ·OH in the real waters by the (highly diluted) EPs must be very inefficient, so removal of EPs cannot purely rely on the generation and reaction of ·OH. This suggests that more complex pathways have to be considered to explain the photodegradation of EPs actually achieved under the employed oxidative conditions, possibly involving other reactive species with longer lifetimes or chain degradation processes. 相似文献