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951.
X W Yang H Miyashiro M Hattori T Namba Y Tezuka T Kikuchi D F Chen G J Xu T Hori M Extine 《Chemical & pharmaceutical bulletin》1992,40(6):1510-1516
From the stems of Kadsura heteroclita, two new lignans named heteroclitins F and G were isolated and their structures were determined by various spectroscopic means including an X-ray diffraction method. Dibenzocyclooctadiene type lignans and related compounds isolated from the stems of K. heteroclita, potently inhibited the lipid peroxidation in the rat liver homogenate stimulated by Fe(2+)-ascorbic acid, CCl4-reduced form of nicotinamide adenine dinucleotide phosphate (NADPH) and adenosine 5'-diphosphate-NADPH. 相似文献
952.
R Mariot L Zangirolami P Bellato S Chen G Pieraccini G Moneti 《Journal of chromatography. A》1992,576(1):143-148
Two methods for the determination of cloricromene acid in biological samples are described. Cloricromene acid is a catabolite of cloricromene, a coumarin derivative which is active in the cardiovascular system. After oral administration of cloricromene to a rabbit, plasma and platelets were taken at different times and cloricromene acid was then isolated by solid-phase extraction with Sep-Pak C18 cartridges using acetonitrile-tetrahydrofuran-20% aqueous acetic acid (15:11:74, v/v/v) as eluent. The analyses were performed by reversed-phase high-performance liquid chromatography (RP-HPLC) combined with fluorescence detection with excitation at 310 nm and emission at 390 nm. The limit of quantification by RP-HPLC was about 50 pg. The catabolite in the plasma was identified by continuous-flow fast atom bombardment mass spectrometry (CF-FAB-MS), also used as a complementary means of RP-HPLC determination. The results obtained by RP-HPLC and CF-FAB-MS showed good agreement. 相似文献
953.
CeO2及Pt/CeO2催化剂上H2、O2的作用特性 总被引:12,自引:1,他引:12
采用TPD、TPR、FT-IR和TPEC等方法研究了CeO_2及Pt/CeO_2上H_2、O_2作用特性。结果表明, Pt促进CeO_2还原, 并形成高活动性氢物种。Pt的存在使吸H_2和放氢温度下阵达300 ℃。部分还原的CeO_2常温下吸附氧形成分子离子氧物种(O_2~-, O_2~(2-)), Pt的存在改变氧化铈催化剂在常温下氧吸附物种的形态, 以解离态存在。氧化铈上吸附的氧物种在升温时可部分脱附, 高于170 ℃时则转化为晶格氧。 相似文献
954.
多硝基多氨基三唑类衍生物作为含能材料,具有高氮、致密、钝感等优点。本文通过3-氨基-1,2,4-三唑和三硝基三氯苯的缩合,再经过三唑碳原子上的硝化反应和芳环上的氨化反应,合成并鉴定了标题化合物。 相似文献
955.
Sven J. Cyvin Bjørg N. Cyvin Jon Brunvoll Rong-Si Chen 《Monatshefte für Chemie / Chemical Monthly》1989,120(10):833-847
Summary Classes of coronoids (or degenerate coronoids), r and q are obtained by providing the rectangle-shaped benzenoids Rj (m, 3) with a naphthalenic or pyrenic hole, respectively. The numbers of Kekulé structures (K) are studied. It was found for theK numbers of the classes in question:r=4/5R andq=1/5R. The classes r and q are similar to r and q, respectively, but the naphthalenic or pyrenic hole is oriented in a different way. For these classes it was found:r=3/5R,q=2/5R.
Die Anzahl von Kekulé-Strukturen für hochkondensierte Benzenoide mit rechteckigem Umriß, 8. Mitt.: Einige perforierte benzenoide Rechteck-Strukturen
Zusammenfassung Es werden Klassen r und q von Coronoiden (oder degenerierten Coronoiden) erhalten, wobei Benzenoide mit rechteckigem Umriß, Rj(m, 3), mit einem Naphthalin- oder Pyren-Loch versehen werden. Die Anzahl von Kekulé-Strukturen (K) wird untersucht; dabei wurde für die untersuchten Klassenr=4/5R undq=1/5R gefunden. Die Klassen r und q verhalten sich ähnlich, das Naphthalin- oder Pyren-Loch ist jedoch anders orientiert; dafür wurder=3/5R undq=2/5R gefunden.相似文献
956.
Eight novel compounds were synthesized by a facile and mild method with high yields, and the structures of all the compounds were characterized by 1H NMR IR mass and high resolution mass spectroscopy. Their inhibitory activity against insect-flight and trehalase in vitro were screened. Some target compounds have moderate inhibitory activity against trehalase, and show inhibition action to insect-flight. 相似文献
957.
Klapars A Waldman JH Campos KR Jensen MS McLaughlin M Chung JY Cvetovich RJ Chen CY 《The Journal of organic chemistry》2005,70(24):10186-10189
[reaction: see text] A mild and transition-metal-free method for the alpha-arylation of aliphatic nitriles with activated heteroaryl halides was developed using NaHMDS or KHMDS as base at ambient temperature. The key to the success of this method is generation of the nitrile anion in the presence of the heteroaryl halide. The method is applicable to both primary and secondary carbonitriles and a wide range of heteroaryl halides. Selective monoarylation was observed with primary carbonitriles. The operational simplicity and the mild reaction conditions add to the value of this method as a practical alternative to the preparation of alpha-heteroaryl carbonitriles. 相似文献
958.
trans-RhCl(CO)(TPPTS)2 (TPPTS=tris(m-sulfonatophenyl)phosphine) has been intercalated into Zn-Al layered double hydroxides (LDHs) by the method of ion exchange. The structure, composition and thermal stability of the composite material have been characterized by powder X-ray diffraction, Fourier transform infrared and 31P solid-state magic-angle spinning nuclear magnetic resonance spectroscopy, elemental analysis, thermogravimetry, and differential thermal analysis. The geometry of trans-RhCl(CO)(TPPTS)2 was fully optimized using the PM3 semiempirical molecular orbital method, and a schematic model for the intercalated species has been proposed. The thermal stability of trans-RhCl(CO)(TPPTS)2 is significantly enhanced by intercalation, which suggests that such materials may have prospective application as the basis of a supported catalyst system for the hydroformylation of higher olefins. 相似文献
959.
ZrO2在Cu-ZnO-ZrO2甲醇水蒸汽重整制氢催化剂中的作用 总被引:2,自引:0,他引:2
通过对一系列Cu-ZnO-ZrO2甲醇水蒸汽重整(SRM)催化剂的XRD、TEM和BET表征及催化性能测定,研究催化剂中ZrO2对催化剂粒径、比表面以及对SRM反应性能的影响.结果表明,ZrO2的加入,使催化剂的粒径从15 nm降至10 nm(其中CuO和ZnO的平均粒径分别从7.7和10.4 nm降至3.9和8.7 nm),BET比表面从60 m2•g-1增至78 m2•g-1.随着催化剂含ZrO2量不同,甲醇的转化率和H2、CO2的选择性均产生变化,当催化剂中Zr含量为24.0%(w),反应温度为220 ℃,水、醇摩尔比为1.3时,甲醇的转化率达到51.6%, H2和CO2的选择性达到100%(CO和CH4在产物气体中的体积分数小于10-4),这一结果对甲醇燃料电池甲醇重整器的应用具有重要的意义. 相似文献
960.
Chen W Wu H Bernard D Metcalf MD Deschamps JR Flippen-Anderson JL MacKerell AD Coop A 《The Journal of organic chemistry》2003,68(5):1929-1932
Treatment of 5-trimethylsilylthebaine with L-Selectride gave rise to a rearrangement to 10-trimethylsilylbractazonine through migration of the phenyl group, whereas treatment of thebaine with strong Lewis acids is known to lead to a similar rearrangement through migration of the alkyl bridge to give, after reduction, (+)-neodihydrothebaine. It is suggested that the rearrangement of the alkyl group of thebaine is favored due to the formation of a tertiary benzylic cation. However, for 5-trimethylsilylthebaine, the lithium ion of L-Selectride acts as the Lewis acid and the beta-silyl effect dominates in the stabilization of any positive charge. This rearrangement provides a clear example of the greater relative migratory aptitude of phenyl groups over alkyl groups, and provides an efficient synthesis of (+)-bractazonine from thebaine. 相似文献