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991.
The scandium-bipyridine-catalyzed enantioselective addition of anilines and O-alkyl hydroxylamines to meso-epoxides has been optimized and extended to a broad range of epoxides and amines. Whereas aromatic meso-epoxides generally furnished the corresponding 1,2-amino alcohols in excellent enantioselectivities, aliphatic meso-epoxides only gave rise to moderate enantioselectivities in the aminolysis. The catalyst loading may be lowered to just 5 mol% with only marginal effects on yield and enantioselectivity. A strong positive nonlinear effect has been observed, pointing to aggregation phenomena of the catalyst. 相似文献
992.
Nakajima K Ohta K Mostefaoui TA Chai W Utsukihara T Horiuchi CA Murakami M 《Journal of chromatography. A》2007,1161(1-2):338-341
Some difficulties on a sampling of gaseous glyoxal using DNPH-silica cartridge were discussed, and an alternative sampling procedure was proposed. When glyoxal was sampled using the cartridge, it partially formed mono-hydrazone with various degrees, whereas it was quantitatively converted into its bis-hydrazone when sample gas was directly bubbled into a DNPH acidic solution. Additionally, glyoxal polymerized on the inner wall of the system during trapping to the silica cartridge. We found that the polymerization of glyoxal was effectively suppressed by dissolving glyoxal into methanol under reduced pressure; glyoxal in methanol readily reacted with DNPH in a hydrochloric acid solution and gave bis-hydrazone derivative, without any interference of methanol and any formation of mono-hydrazone derivative. When glyoxal was sampled by the proposed method, 102% of recovery was obtained, whereas it was reduced to 92.7% when the trapped glyoxal was dissolved into methanol under atmosphere. 相似文献
993.
An efficient copper-catalyzed double alkenylation of amides with (1Z,3Z)-1,4-diiodo-1,3-dienes is reported for the first time. The reactions proceed to afford di- or trisubstituted N-acylpyrroles in good to excellent yields using CuI as the catalyst, Cs2CO3 as the base, and rac-trans-N,N'-dimethylcyclohexane-1,2-diamine as the ligand. 相似文献
994.
Jiehua Mai 《Topology and its Applications》2007,154(11):2306-2311
Let G be a graph and be continuous. Denote by P(f), , ω(f) and Ω(f) the set of periodic points, the closure of the set of periodic points, ω-limit set and non-wandering set of f, respectively. In this paper we show that: (1) v∈ω(f) if and only if v∈P(f) or there exists an open arc L=(v,w) contained in some edge of G such that every open arc U=(v,c)⊂L contains at least 2 points of some trajectory; (2) v∈ω(f) if and only if every open neighborhood of v contains at least r+1 points of some trajectory, where r is the valence of v; (3) ; (4) if , then x has an infinite orbit. 相似文献
995.
From the work of Simmons about nuclei in frames it follows that a topological space X is scattered if and only if each congruence Θ on the frame of open sets is induced by a unique subspace A so that , and that the same holds without the uniqueness requirement iff X is weakly scattered (corrupt). We prove a seemingly similar but substantially different result about quasidiscrete topologies
(in which arbitrary intersections of open sets are open): each complete congruence on such a topology is induced by a subspace
if and only if the corresponding poset is (order) scattered, i.e. contains no dense chain. More questions concerning relations
between frame, complete, spatial, induced and open congruences are discussed as well.
Dedicated to Bernhard Banaschewski. 相似文献
996.
Nagaoka S Fujii A Hino M Takemoto M Yasuda M Mishima M Ohara K Masumoto A Uno H Nagashima U 《The journal of physical chemistry. B》2007,111(45):13116-13123
The UV protection and singlet oxygen quenching of aloesaponarin I have been studied by means of laser spectroscopy. The excited-state intramolecular proton transfer that provides the UV protection takes place along only one of the molecule's two intramolecular hydrogen bonds, and this can be understood by considering the nodal pattern of the wave function. The functional groups participating in the excited-state intramolecular proton transfer also play important roles in the singlet oxygen quenching. Aloesaponarin I has a quenching rate constant larger than that of vitamin E and has a long duration of action due to its resistance to UV degradation and chemical attacks by singlet oxygen and free radicals. 相似文献
997.
998.
The quest for athletic excellence holds no limit for some athletes, and the advances in recombinant DNA technology have handed these athletes the ultimate doping weapons: recombinant proteins and gene doping. Some detection methods are now available for several recombinant proteins that are commercially available as pharmaceuticals and being abused by dopers. However, researchers are struggling to come up with efficient detection methods in preparation for the imminent threat of gene doping, expected in the 2008 Olympics. This Forum article presents the main detection strategies for recombinant proteins and the forthcoming detection strategies for gene doping as well as the prime analytical challenges facing them. 相似文献
999.
1000.
Hiroyoshi Kawakami Kazue Hiraka Miho Tamai Aiko Horiuchi Akihiko Ogata Tomomi Hatsugai Aritomo Yamaguchi Kenichi Oyaizu Makoto Yuasa 《先进技术聚合物》2007,18(1):82-87
In this article the novel design of an anticancer drug delivery system is reported based on a pH‐sensitive liposome retaining the Fe‐porphyrin as a superoxide dismutase(SOD) mimic. The liposomes contained cationic/anionic lipid combinations and were composed of Fe‐porphyrin, L ‐α‐phosphatidylcholine (DMPC), dimethylditetradecylammonium bromide (DTDAB), sodispdum oleate (OANa), and Tween‐80. The size of the liposome was approximately 30 nm. The EC50 value (the effective concentration of compound required to produce a 50% lethal dose against cells) of the liposome was found to be significantly smaller than that of cisplatin as the control drug, suggesting that the liposome showed a high cytotoxicity toward the cancer cells. This is due to the fact that the pH‐sensitive liposome rapidly corresponds to the acidic environments of the endosomes and is unstable, and the Fe‐porphyrin is delivered into the cytosol. This result suggests that O may be useful as a target molecule to induce the selective death of cancer cells and that a pH‐sensitive liposome retaining Fe‐porphyrin as an SOD mimic is a new class of anticancer agent. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献