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121.
Ngouela S Zelefack F Lenta BN Ngouamegne ET Tchamo DN Tsamo E Connolly JD 《Natural product research》2005,19(7):685-688
A xanthone derivative, 3,6,7-trihydroxy-1-methoxyxanthone has been isolated from the stem bark of Allanblackia monticola together with other known compounds, 2,6-dihydroxy-1-methoxyxanthone, allanxanthone A, epicathechin and oleanolic acid acetate. The structure of the new compound was elucidated by spectroscopic methods. 相似文献
122.
New Phellandrene Derivatives from the Root Oil of Angelica archangelica L . 2-Nitro-1,5-p-menthadiene ( 5 ), trans- and cis-6-nitro-1(7), 2-p-menthadiene ( 6 and 7 ), trans-1(7), 5-p-menthadien-2-yl acetate ( 9 ) and a formal phellandrene derivative, 7-isopropyl-5-methyl-5-bicyclo [2.2.2]octen-2-one ( 16 ), have been identified in the root oil of Angelica archangelica L . Starting from (?)-(R)-α-phellandrene ( 1 ) (R)- 5 , (4R, 6S)- 6 /(4R, 6R)- 7 , (2S, 4R)- 9 and (1R, 4R, 7R)- 16 as well as (2S, 4R)- 11 , (2R, 4R)- 12 and (2R, 4R)- 10 have been prepared. 相似文献
123.
Enamino- and Halogenoacetylenic sugars Traitment of an aldehydosugar ( 1 ) with secondary amines gave in an essentially quantitative yield the expected enamines ( 4–6 ). Chloro- and bromo-acetylenic sugars ( 11–14 ) were obtained in good yields by reacting with lithium methylphenylamide the corresponding gem-dihalo-olefinic sugars ( 7–10 ), whereas a Z-gem-fluoro-enamine ( 17 ) was formed when the difluoro-olefinic sugar 15 was submitted to the same reaction. The fluoro-enamine 17 is a useful synthetic intermediate allowing the preparation of several kinds of C-glycosylic compounds bearing heterocycles like isoxazole, chromone or coumarin. 相似文献
124.
125.
Chryss Chryssomalakos Bernhard Drabant Michael Schlieker Wolfgang Weich Bruno Zumino 《Communications in Mathematical Physics》1992,147(3):635-646
Using previous results we construct theq-analogues of the left invariant vector fields of the quantum enveloping algebra corresponding to the complex Lie algebras of typeA
n–1
,B
n
,C
n
, andD
n
. These quantum vector fields are functionals over the complex quantum groupA. In the special caseA
1 it is shown that this Hopf algebra coincides withU
q
sl(2, ). 相似文献
126.
A series of new esters of lutein ( 1a ) have been prepared with the aim of confirming the structure of lutein via an X‐ray crystal‐structure analysis. Although well crystallized, only one of the derivatives, the (?)‐(1R)‐menthyl carbonate ( 1i ) proved to be useful for a complete structure analysis. The same derivative of zeaxanthin ( 2a ) also allowed its crystal structure to be determined. Both analyses represent the first successful X‐ray crystal structure analyses of the most important xanthophylls. At the same time, they confirm both the constitution and absolute configuration of 1a and 2a that had been deduced earlier by classical methods. 相似文献
127.
Sylviane Sabo Bruno Chaudret Danièle Gervais 《Journal of organometallic chemistry》1985,292(3):411-418
The possibility of making metal—metal bonded heterobimetallic species by metathesis of ruthenium dichlorides with anionic carbonylates is demonstrated by the isolation of MoRu(μ-Cl)(μ-CO)(CO)2(PPh3)2(η-C5H5) (1) and MnRuCl(μ-CO)2(CO)3(μ-dppm)2 (2), obtained by action of [Mo(CO)3(η-C5H5]? on RuCl2(PPh3)3 and of Mn(CO)5? on RuCl2(dppm)2, respectively. In contrast, reaction of Mn(CO)5? with RuCl2(PMe3)4 yielded an ionic species 3 containing the diruthenium cation Ru2Cl3(PMe3)6+. More interestingly, the action of Mn(CO)5? on RuCl2(PPh3)3 resulted in the formation of the unexpected complex MnRu(μ-PPh2)(CO)6(PPh3)2 (4) in which the phosphido group PPh2 bridges the two metals; this process is shown to involve a hydride intermediate, and elimination of a molecule of benzene, both identified in the reaction mixture. 相似文献
128.
Bradley M Bruno N Vincent B 《Langmuir : the ACS journal of surfaces and colloids》2005,21(7):2750-2753
CdSe quantum dots (QDs) are semiconducting nanoparticles that fluoresce when stimulated by visible light. This property has been exploited in their use as tracer particles in biomedical applications. In this study, confocal microscopy has been used to determine the distribution of QDs within polystyrene microgel particles, dispersed in an organic solvent. It was found that the extent of microgel swelling affected the penetration of the QDs into the particles. Only when the microgel particles were swollen to their maximum extent were the QDs able to penetrate into the central core region of the particles. 相似文献
129.
The accuracy, precision, and reproducibility of a rapid method for determination of fluoride in wine, using a fluoride selective ion electrode, were established by a collaborative study involving 12 laboratories, 5 in Europe and 7 in the United States. The laboratories assayed 6 Youden pairs of fluoride-fortified, red and white wine samples with fluoride concentrations ranging from 0.2 to 3.0 mg/L. The relative standard deviations of repeatability ranged from 1.94 to 4.88%; relative standard deviations of reproducibility ranged from 4.15 to 18.40%. HORRAT values ranged from 0.30 to 0.97. The average recovery was 99.97%. Based on the statistical results of this collaborative study, the Study Director recommends that this method be adopted First Action. 相似文献
130.
Enthalpies of mixing of liquid In—Cd alloys were determined over the entire concentration range using a sensitive calorimeter. Deviations of this system from regular behavior can be explained by the existence of associates in the alloy melts. Furthermore the concentration dependence of the enthalpies of mixing were explained, with the help of a previously derived model, by the existence of associates of the composition InCd3. Moreover the possibility was discussed that associates of a different stoichiometric composition occur in liquid In—Cd alloys, by which the discrepancies of earlier experimental results with the isopiestic method can be clarified. 相似文献