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51.
A short and efficient synthesis of 2'-O-methoxyethylguanosine (8) is described. Central to this strategy is the development of a novel silicon-based protecting group (MDPSCl(2), 2) used to protect the 3',5'-hydroxyl groups of the ribose. Silylation of guanosine with 2 proceeded with excellent regioselectivity and in 79% yield. Alkylation of the 2'-hydroxyl group of 6 proceeded with methoxyethyl bromide and NaHMDS and afforded compound 7 in 85% yield, without any noticeable cleavage of the silyl protecting group and without the need to protect the guanine base moiety. Finally, deprotection of 7 was achieved using TBAF and produced 8 in 97% yield. 相似文献
52.
Recalculations of the Gurney free-energy parameters Aij based on the cosphereoverlap model of Friedman and co-workers have been made using more recent experimental data. Our procedure for calculation seems to be more systematic than those previously reported. The excess energy, entropy, and volume parameters (Eij, TSij, and Vij) were also recalculated for some aqueous tetraalkylammonium halides. In addition, the excess-heat-capacity parameters Cij are also reported here for the first time. These data are discussed briefly in terms of the structural implications. 相似文献
53.
54.
Bian HD Gu W Xu JY Bian F Yan SP Liao DZ Jiang ZH Cheng P 《Inorganic chemistry》2003,42(14):4265-4267
The first mu(3)-oxalato-bridged copper(II) complex, [[Cu(3)(L)(3)(mu(3)-C(2)O(4))][Cu(L)(H(2)O)](ClO(4))(2)] x 0.5(H(2)O) x 0.5(CH(3)OH), where HL = N-ethyl-N'-salicylidene-1,2-diaminoethane, has been synthesized and characterized by variable-temperature magnetic susceptibility measurement. The complex exhibits ferromagnetic coupling between the oxalato-bridged copper atoms and antiferromagnetic coupling between the oxygen-bridged copper atoms. 相似文献
55.
Shu Ping XU* Huan Wen CHEN Ai Min YU Qin Han JIN Hua Ying LIAO Changchun R&D Center for Analytical Instruments Department of Chemistry Jilin University Changchun Key Laboratory for Supramolecular Structure Spectroscopy of Ministr 《中国化学快报》2002,13(7):660-661
In recent years, the determination of Cr (VI) has attracted great attention because of its toxicity to human, plants and animals1-5. Usually, in the industrial waste water, the concentration of Cr (VI) is relatively high and should be determined frequently. So, an accurate, quick, and convenient method for the measurement of Cr (VI) in environmental water, as well as in river, lake, sea and tap water, is of great importance. The method for determination of Cr (VI) by diphenylcarbazine … 相似文献
56.
Synthesis of New Chiral C2-Symmetrical Bis(oxazoline )Compounds 总被引:2,自引:0,他引:2
New chiral C2-symmetrical bis(oxazoline)compounds bearing one isobutyl-,secbutyl-benzyl- or isopropyl-substituent at the 4-position have been prepared and characterized. 相似文献
57.
Some organogermanium oligomers with different side groups were synthesized via li-gand substitution polymerization from 1, 4-dioxane complex of germanium dichloride withdifferent organolithitum compounds. The oligomers were isolated through either precipi-tation from methanol or extraction using toluene with a yield of no less than 50%. Theweiglit average molecular weight (M_w) of the oligomers is ranging from 1.4×10~3 to 5.9×10~3depending on the type and alkyl length of the organolithium compounds used. 相似文献
58.
PC/PBT共混体系的研究:Ⅰ.PC,PBT熔融共混时的酯交换反应 总被引:9,自引:0,他引:9
采用红外光谱、核磁共振等测试手段,系统地研究了PC、PBT熔融共混时的酯交换反应,发现PBT中残余的Ti催化剂会对酯交换反应起催化作用。通过加入能和Ti催化剂络合添加剂,可以控制酯交换程度,这为控制PC/PBT合金的性能提供了一个非常有效的方法。 相似文献
59.
The potential-dependent surface-enhanced Raman spectrum of adsorbed p-nitrobenzoic acid (PNBA) on the roughened Au electrode has been obtained by using ultraviolet (UV) excitation at 325 nm. The surface-enhanced Raman spectra of PNBA intensely changed when the voltage was in the rang of negative value, and the electrode potential at which the resonance (potential of maximum intensity) occurs varied when the vibrational mode changes, indicating that the PNBA molecules were chemisorbed on the roughened Au surface. The charge transfer (CT) mechanism could probably explain the experiment results in the present work. 相似文献
60.
Acta Mathematica Sinica, English Series - The main purpose of this article is to study the calculating problem of the sixth power mean of the two-term exponential sums, and give an interesting... 相似文献