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1.
Dr. Carla Carrera Dr. Eleonora Cavallari Dr. Giuseppe Digilio Dr. Oksana Bondar Prof. Silvio Aime Dr. Francesca Reineri 《Chemphyschem》2021,22(11):1042-1048
An efficient synthesis of vinyl-[1-13C]pyruvate has been reported, from which 13C hyperpolarized (HP) ethyl-[1-13C]pyruvate has been obtained by means of ParaHydrogen Induced Polarization (PHIP). Due to the intrinsic lability of pyruvate, which leads quickly to degradation of the reaction mixture even under mild reaction conditions, the vinyl-ester has been synthesized through the intermediacy of a more stable ketal derivative. 13C and 1H hyperpolarizations of ethyl-[1-13C]pyruvate, hydrogenated using ParaHydrogen, have been compared to those observed on the more widely used allyl-derivative. It has been demonstrated that the spin order transfer from ParaHydrogen protons to 13C, is more efficient on the ethyl than on the allyl-esterdue to the larger J-couplings involved. The main requirements needed for the biological application of this HP product have been met, i. e. an aqueous solution of the product at high concentration (40 mM) with a good 13C polarization level (4.8 %) has been obtained. The in vitro metabolic transformation of the HP ethyl-[1-13C]pyruvate, catalyzed by an esterase, has been observed. This substrate appears to be a good candidate for in vivo metabolic investigations using PHIP hyperpolarized probes. 相似文献
2.
Xiao-pingYan Bao-linHe JieZhang Han-fanLiua 《高分子科学》2005,(4):393-399
Modification of transition metal cations to polymer-stabilized Pt colloidal clusters modified with cinchonidine was studied in enantioselective hydrogenation of methyl pyruvate. Compared to the enantiomeric excess (e.e.) value (71.4%) obtained without the presence of metal cations, obvious e.e. enhancement (up to 82.5%) was resulted from the addition of Zn^2 but with a certain decrease in activity. The reaction parameters in the presence of Zn^2 were also studied. It was found that the Pt colloidal catalysts in the presence of metal cations performed very differently from that in the absence of metal cations. 相似文献
3.
Georgiy B. Shul’pin Camilla C. Golfeto Lidia S. Shul’pina 《Tetrahedron letters》2005,46(27):4563-4567
The H2O2-FeCl3-bipy system in acetonitrile efficiently oxidises alkanes predominantly to alkyl hydroperoxides. Turnover numbers attain 400 after 1 h at 60 °C. It has been assumed that bipy facilitates proton abstraction from a H2O2 molecule coordinated to the iron ion (these reactions are stages in the catalytic cycle generating hydroxyl radicals from the hydrogen peroxide). Hydroxyl radicals then attack alkane molecules finally yielding the alkyl hydroperoxide. 相似文献
4.
5.
Summary A fumed silica surface was systematically modified by the grafting of n-alkyl chains with increasing carbon numbers. The samples
were characterized by the dispersive component of the surface energy, their specific interaction potential and enthalpies
of adsorption of polar, in particular, alcohol probes. It is shown that the variation of the surface properties and adsorption
capacities depend on the chain length of the graft. For instance, minimum values are recorded when the surface coverage by
methylene groups corresponds either to one or two CH2 surface layers. This behaviour is related to the mobility of the grafted alkyl chains, mobility which was examined by solid
state NMR. 相似文献
6.
A simple new protocol for the high yielding Suzuki-Miyaura cross-couplings of aryl chlorides with aryl boronic acids using a palladium/imidazolium salt catalytic system is presented. The first examples of a palladium/imidazolium salt protocol for sp3-sp3 Suzuki-Miyaura couplings of alkyl halides are also disclosed. 相似文献
7.
Luigi Ambrosone Lucia Costantino Gerardino D'errico Vincenzo Vitagliano 《Journal of colloid and interface science》1997,190(2):286
The densities and viscosities of binary aqueous mixtures of poly(ethylenoxide)hexanols [C6H13(OCH2CH2)mOH, C6Em] (m= 3, 4, and 5) have been studied in the micellar composition range. For the same surfactants the self-diffusion coefficients in mixtures with heavy water have been determined by the spin-echo pulsed field gradient method. The volumetric data are interpreted by means of the phase separation model, and values of the CMC, volume change, and standard free energy change of micellization are obtained. From the viscosity data the hydration numbers of the surfactant hydrophilic head in the micellar state are computed; they are in agreement with those obtained from HDO self-diffusion data. The surfactant self-diffusion data are used to calculate the apparent micelle radius and the aggregation number. The micellization parameters obtained for the different surfactants are compared and discussed. 相似文献
8.
Alkyl ketene dimer (AKD) sizing of paper involves the redistribution of the wax over the fibre surface upon heating. The two
major mechanisms widely studied so far are the spreading of an autophobic precursor of molten AKD and AKD vapour transport
and re-deposition on the fibre surface. All previous work assumed that the transport of AKD vapour could be expressed by the
change of water contact angle with substrates that were exposed to the vapour. Information regarding the chemical composition
of the vapour phase above the AKD wax has not been found in the literature. In this work, a simple method for analysing the
chemical composition of the vapour is established. Our preliminary results indicated that the chemical composition of AKD
vapour in the temperature range of 75–80 °C is dominantly fatty acids. This suggests that the sizing effect by actual AKD
molecules via the vapour deposition mechanism is likely to be insignificant in this temperature range. This also implies that
fatty acids play a positive role in AKD sizing. The chemical stability of AKD in this temperature range is also studied. 相似文献
9.
Mohamed R. Mahran Wafaa M. Abdou Maha D. Khidre 《Monatshefte für Chemie / Chemical Monthly》1990,121(1):51-58
Summary The reaction of furil (1) with trialkyl phosphites2 yielded caged phosphorane derivatives of types3a-c. Dry hydrogen chloride gas converted3a-c into the respectivea-hydroxyvinyl-phosphates8a-c which are equally produced by reacting furil with the appropriate dialkyl phosphite7. The reaction of furil with ylide-phosphoranes10 proceeded according to the Wittig reaction mechanism to give the respective ethylenes11a-c. The new compounds have been characterized by their spectroscopic data (IR, PMR,31P-NMR, MS) and elementary analyses.Dedicated to Prof. M. Sidky on the occasion of his 60th birthday 相似文献
10.
Summary A theoretical treatment is presented which considers differences between the composition of the mobile phase and solvents
that are incorporated into the bonded phase via preferential sorption. Equations are derived and used to analyze retention
data for various homologs chromatographed under reversed-phase conditions using alkyl bonded phases and combinations of water-methanol,
water-acetonitrile and watertetrahydrofuran as mobile phases. In the case of water-methanol the surface phase and bulk mobile
phase compositions are similar. However, significant differences in composition between the two phases are observed when binary
combinations of water-acetonitrile and water-tetrahydrofuran are used as the cluents. 相似文献