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61.
Cerebrosterol (2 4S hydroxycholesterol,1)formedinsmallamountsinhumanandanimalbrain1fromcholes terolisimportantforcholesterolhomeostasisinthisorgan .Theexcesscholesterolisconvertedinto 2 4S hydroxy cholesterolbyauniquebrain specific 2 4S hydroxylase ,whichcouldber… 相似文献
62.
Dan Donescu Sever Serban Kristiana Gosa Cristian Petcu 《Central European Journal of Chemistry》2005,3(1):10-27
The possibility to prepare hybrids made by poly(vinyl acetate) (PVAc), poly(methyl methacrylate) (PMMA) and/or poly(ethyl
acrylate) (PEtA) with TiO2 was studied. The processes of polymer formation-radical polymerization and sol-gel process for inorganic network —were achieved
simultaneously. Due to a high reactivity of titanium isopropoxide (TIP) in the sol-gel process, a complexant comonomer, allyl
acetoacetate (AlAcAc), was used. Covalent bonds between polymer and inorganic chains were obtained by addition of trialkoxysilane
derivates with vinyl (VTES) or methacryloyl (MPTS) groups. The presence of TIP inhibits the radical polymerization of vinyl
acetate (VAc). The PVAc-TiO2 hybrids were produced by the sol-gel process of TIP in the presence of pre-obtained PVAc. Except for VTES and MPTS, trialkoxysilane
derivates with methyl (MeTES), octyl (OTES) and phenyl (PTES) groups were used. The thermal stability of hybrids is strongly
affected by TiO2 presence and by the type of trialkoxysilane derivates. The thermal stability of PVAc hybrids decreases in the presence of
TiO2 inorganic network. The glass transition temperature of polymers increases in the presence of the inorganic network. 相似文献
63.
N. Ya. Grigorieva 《Russian Chemical Bulletin》2005,54(4):1046-1047
High (Z)-stereoselectivity of olefination of methyl α-phenylthioalkyl and methyl α-phenylthioalkenyl ketones with methyl trimethylsilylacetate
decreases in the case of ketones containing a higher alkyl-substituent in place of the methyl group.
Dedicated to Corresponding Member of the Russian Academy of Sciences E. P. Serebryakov on the occasion of his 70th birthday.
__________
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 1020–1021, April, 2005. 相似文献
64.
Migration behavior and enantioseparation of racemic hydrobenzoin and structurally related compounds, including benzoin and benzoin methyl ether, in CZE with a dual CD system consisting of heptakis-(2,3-dihydroxy-6-O-sulfo)-beta-CD (SI-S-beta-CD) and beta-CD as chiral selectors in the presence and absence of borate complexation at pH 9.0 were investigated. The results indicate that enantioseparation of hydrobenzoin is mainly governed by CD complexation of hydrobenzoin-borate complexes with SI-S-beta-CD when SI-S-beta-CD concentration is relatively high. Whereas CD complexation of hydrobenzoin-borate complexes with beta-CD plays a significant role in enantioseparation when SI-S-beta-CD concentration is comparatively low. The (S,S)-enantiomer of the hydrobenzoin-borate complex was found to interact more strongly than the corresponding (R,R)-enantiomer with both SI-S-beta-CD and beta-CD. These two types of CD show the same chiral recognition pattern, but they exhibit opposite effects on the mobility of the enantiomers of hydrobenzoin-borate complexes. Enantiomer migration reversal of hydrobenzoin occurred in the presence of borate complexation when varying the concentration of beta-CD, while keeping SI-S-beta-CD at a relatively low concentration. Binding constants of the enantiomers of benzoin-related compounds to beta-CD and those of hydrobenzoin-borate complexes to SI-beta-CD were evaluated; the mobility contributions of all complex species to the effective mobility of the enantiomers of hydrobenzoin as a function of beta-CD concentration in a borate buffer were analyzed. In addition, comparative studies on the enantioseparation of benzoin-related compounds with SI-S-beta-CD and with randomly sulfate-substituted beta-CD were made. 相似文献
65.
A. K. Umbetova M. I. Choudhary N. A. Sultanova G. Sh. Burasheva Zh. A. Abilov 《Chemistry of Natural Compounds》2006,42(3):332-335
The taraxeran-14-ene-type triterpenoids methyl 3-β-al-D-fridoolean-14-en-28-oate (1), 3-α-[3″,4′-dihydroxytrans-cinnamoyl]-oxy-D-fridoolean-14-en-28-oic acid (2), and β-sitosterol (3) were isolated from the aerial part of plants from the genus Tamarix (T. laxa, T. elongata) (Tamaricaceae). The structures of the triterpenoids were proved using spectral data (IR, UV, PMR, 13C NMR, 2D NMR 1H-1H COSY, HMQC, HMBC, mass). Compound 1 is new and not previously described in the literature.
__________
Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 271–273, May–June, 2006. 相似文献
66.
Shi Zhen CHEN Yun Peng BAI Zhao Long LI 《中国化学快报》2006,17(2):258-260
Fluorous-phase chemistry is currently a topic of considerable interest1-6. Since fluoroustriphasic reactions were first described by the Curran and co-workers7, this triphasicsystem has been widely used for detagging7,8 and phase-vanishing reactions9-11. … 相似文献
67.
Mingzhu Liu Rongshi Cheng Jingjia Wu Cheng Ma 《Journal of polymer science. Part A, Polymer chemistry》1993,31(13):3181-3186
A study was made of the ceric ammonium nitrate (CAN) initiated graft copolymerization of methyl acrylate (MA) onto potato starch. The variables affecting the graft were investigated. The optimums have been obtained; they are the concentrations of MA, CAN, and nitric acid (HNO3) (1.08, 5.0 × 10?3, and 0.081 mol/L, respectively). The reaction temperature is ca. 50°C and the reaction time is 2 h. The molecular weight of grafted poly(methylacrylate) has been determined. On the basis of experimental results, the mechanism of grafting has been explored, a new kinetic equation of the graft copolymerization is established: Rp = Kkd [STOH] [Ce4+] + Kkpkd/kt[STOH][M], where K, kd, kp, and kt are constants. The equation fits the results of experiments. © 1993 John Wiley & Sons, Inc. 相似文献
68.
The determination of nanometer thick layers of poly(methyl methacrylate) coated on to the surface of poly(ethylene terephthalate) film has been investigated by high resolution pyrolysis gas chromatography without sample pretreatment or modification of the instrumentation used. A good linear relationship was observed between the quantity of the characteristic pyrolysate and the thickness of the poly(methyl methacrylate) layer; the detection limit was sufficient to enable the quantitation of poly(methyl methacrylate)-to-poly(ethylene terephthalate) film thickness ratios of 1:20000 in composite materials. 相似文献
69.
JianGouHUANG ManCaiXU HaiTaoLI ZuoQingSHI 《中国化学快报》2003,14(9):914-916
Two polymeric adsorbents, poly(methyl p-vinylbenzvl ether) and oolv(ohenvl p-vinylbenzyl ether), were synthesized from chloromethylated polystyrene, Their adsorptionproperty for phenol in hexane solution was investigated. The results showed that the twoadsorbents adsorb phenol from hexane solution through hydrogen-bonding and π-π stacking interaction. 相似文献
70.
The emeraldine base form of polyaniline (PANI) can be doped by a photo-induceddoping method. In this method a copolymer of vinylidene chloride and methyl acrylate(VCMAC) was used as photo acid generator which can release proton when it is exposedto ultraviolet light (λ= 254 nm). The structure of PANI-VCMAC system before and afterirradiation was characterized by elemental analysis, IR, XPS, and SEM images. Resultsobtained indicate that the photo-induced doping characteristics, such as doping positionand type of charge carriers, are similar to that of PANI doped with HCl. The poor room-temperature conductivity (~10~(-5)S/cm) of PANI-VCMAC system after irradiation maybe due to low doping degree (~pH= 3) and the difference in morphology as compared withPANI-HCl film. 相似文献