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151.
A new serratane-type triterpene, lycophlegmarin (1), has been isolated from Lycopodium phlegmaria L. Four known related triterpenoids were also found from the title plant. The structure of the new compound was elucidated on the basis of detailed spectroscopic analysis and chemical method. Lycophlegmarin exhibited modest growth-inhibitory activity in vitro against human hepatoma cells BEL 7402. 相似文献
152.
铈、镨二乙基磷酸盐的晶体结构 总被引:1,自引:0,他引:1
合成了Ce[PO_2(OC_2H_5)_2]_3和Pr[PO_2(OC_2H_5)_2]_3(简称Ce(DEP)_3和Pr(Pr(DEP)_3)。用四圆衍射仪测定了其晶体结构。它们均属三斜晶系,空间群P1。晶胞参数,对Ce(DEP)_3:α=10.324(4)A,b=12.861(4)A,c=13.998(5)A,x=106.49(3)°,β=112.83(4)° γ=115.61(3)°,V=1296(1)A~3,Z=2;对Pr(DEP)_3:α=10.27(1)A,b=11.81(1)A,c=12.51(1)A,x=109.93(9)°,β=111.9(9)°,γ=93.0(1)°,V=1293(3)A~3,Z=2。用Patterson法并经分块全矩阵最小二乘法修正,最后的R值,Ce的为0.1071,Pr的为0.1066。结构分析指出,两种配合物结构类似,Ce和Pr原子均由二乙基磷酸根的六个氧原子配位形成八面体构型。 相似文献
153.
含氢硅氧烷的硅氢加成反应 总被引:2,自引:0,他引:2
含氢硅氧烷的硅氢加成反应师彤,谢择民,王清正(中国科学院化学研究所北京100080)关键词含氢硅氧烷,二乙烯基四甲基二硅氧烷,硅氢加成反应,~1HNMR铂催化硅氢加成的机理~[1,2]、副反应 ̄[3,4]、聚合物性能 ̄[3,5]等均有报道,个别文献用粘?.. 相似文献
154.
A mesoporous template route to the low-temperature preparation of efficient green light emitting Zn2SiO4:Mn phosphors 总被引:1,自引:0,他引:1
Xiong L Shi J Gu J Li L Huang W Gao J Ruan M 《The journal of physical chemistry. B》2005,109(2):731-735
Green light emitting Zn2SiO4:Mn phosphors have been prepared via a low-temperature solid-state reaction using mesoporous silica SBA-15 template. This mesoporous silica template method features low-temperature formation of phosphors and easy doping. The structure and morphology of the phosphors were characterized by XRD, SEM, TEM, and N2 adsorption/desorption techniques, which confirmed the single crystallinity, ordered mesostructure, closed pore channels, and elongated ropelike morphology. The luminescent properties were examined by photoluminescence spectroscopy at room temperature, and the results of fluorescence decay time measurements show non-single-exponential decay behavior and a decrease of the decay time with an increase of the Mn concentration. 相似文献
155.
QSAR models using a large diverse set of estrogens 总被引:12,自引:0,他引:12
Shi LM Fang H Tong W Wu J Perkins R Blair RM Branham WS Dial SL Moland CL Sheehan DM 《Journal of chemical information and computer sciences》2001,41(1):186-195
Endocrine disruptors (EDs) have a variety of adverse effects in humans and animals. About 58,000 chemicals, most having little safety data, must be tested in a group of tiered assays. As assays will take years, it is important to develop rapid methods to help in priority setting. For application to large data sets, we have developed an integrated system that contains sequential four phases to predict the ability of chemicals to bind to the estrogen receptor (ER), a prevalent mechanism for estrogenic EDs. Here we report the results of evaluating two types of QSAR models for inclusion in phase III to quantitatively predict chemical binding to the ER. Our data set for the relative binding affinities (RBAs) to the ER consists of 130 chemicals covering a wide range of structural diversity and a 6 orders of magnitude spread of RBAs. CoMFA and HQSAR models were constructed and compared for performance. The CoMFA model had a r2 = 0.91 and a q2LOO = 0.66. HQSAR showed reduced performance compared to CoMFA with r2 = 0.76 and q2LOO = 0.59. A number of parameters were examined to improve the CoMFA model. Of these, a phenol indicator increased the q2LOO to 0.71. When up to 50% of the chemicals were left out in the leave-N-out cross-validation, the q2 remained significant. Finally, the models were tested by using two test sets; the q2pred for these were 0.71 and 0.62, a significant result which demonstrates the utility of the CoMFA model for predicting the RBAs of chemicals not included in the training set. If used in conjunction with phases I and II, which reduced the size of the data set dramatically by eliminating most inactive chemicals, the current CoMFA model (phase III) can be used to predict the RBA of chemicals with sufficient accuracy and to provide quantitative information for priority setting. 相似文献
156.
157.
研究了氟离子选择电极瞬时电位分析法,其检出限和Nernst响应下限均低于传统电位分析法,空白液切换到试液时瞬时电位达到稳定的峰电位Vp比传统电位法的响应快得多,可以实现小体积试液的快速准确分析;用该法测定了自来水和矿泉水中氟的含量;利用校正曲线的截距和检出限计算了LaF3的溶度积,在0.1mol/L KNO3介质中Ksp(LaF3)=10^-28.45,在0.001mol/L柠檬酸钠+HAc-NaAc缓冲液(pH=5.50,离子强度I=0.10mol/L)介质中溶度积K′sp(LaF3)=10^-26.26;据此,计算得柠檬酸与La^3 络合物的稳定常数K1=10^5.46和K2=10^3.99;用离子水合吉氏自由能ΔGh(F^-,g)解释了不同浓度F^-试液瞬时电位的跃迁时间。 相似文献
158.
Treatment of 4-nitrophenyl chloroformate with alkylammonium hydrochloride salts and solid anhydrous Na2CO3 in either CH2Cl2 or CH3CN gave 4-nitrophenyl N-methylcarbamate and other N-alkylcarbamate analogues in excellent yields. Of particular interest is the observation that 4-nitrophenyl N-methylcarbamate, a safer alternative to the highly toxic methyl isocyanate, is obtained in quantitative yield (?95% pure as determined by 1H NMR) after simple filtration and solvent evaporation. 相似文献
159.
Nian Yun YANG Shi Hui QIAN Jin Ao DUAN Ping LI Li Juan TIAN Jiangsu Academy of Traditional Chinese Medicine Nanjing China Pharmaceutical University Nanjing Jinling Pharmaceutical Company Limited Nanjing 《中国化学快报》2005,16(9)
Various germacrane sesquiterpenes have been isolated from many species of the Eupatorium.In recent years these compounds have been increasing interest due to their insecticidal,cytotoxic,antitumor-promoting and insect-antifeedant activities1.In our present study,we have investigated the chemical constituents of Eupatorium lindleyanum DC.,which is a geo-authentic medicine of Jiangsu province.It is used as a antipyretic drug.Two novel germacrane sesquiterpenes(Figure1)were found by us from th… 相似文献
160.
The attempted Baylis-Hillman reactions of N-tosyl aldimines and aryl aldehydes with 3-methylpenta-3,4-dien-2-one gave the corresponding Baylis-Hillman adducts 3 and 6 in moderate to good yields in the presence of DMAP in DMSO, respectively. In the case of the aza-Baylis-Hillman reactions of N-tosyl aldimines with 3-methylpenta-3,4-dien-2-one catalyzed by PBu3, the corresponding aza-Baylis-Hillman derivatives 4 and 5 were formed at the same time. 相似文献