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991.
Zhenshan Jia Xiang Zhang Gaihong Zhang Shaohua Huang Hao Fang Xiangqing Hu Yuliang Li Prof. Liangbing Gan Prof. Shiwei Zhang Prof. Daoben Zhu Prof. 《化学:亚洲杂志》2007,2(2):290-300
The Cs‐symmetric fullerene chlorohydrin C60(Cl)(OH)(OOtBu)4 reacts with 4‐dimethylaminopyridine (DMAP) and 1,4‐diazabicyclo[2.2.2]octane (DABCO) to yield two isomers with the formula C60(O)(OOtBu)4 in good yields. These isomers differ with respect to the location of the epoxy functionality. The one from DMAP is Cs symmetric, whereas that from DABCO is C1 symmetric with the epoxy group on the central pentagon. Two different mechanisms are proposed to explain the chemoselectivity of these reactions. The reaction with DMAP involves single‐electron transfer as the key step; DMAP acts as the electron donor. A combination of an oxygen‐atom shift and SN2′′ processes (boomerang substitution) are responsible for the formation of isomer with DACBO. Various related reactions support the proposed mechanisms. The structures of new fullerene derivatives were determined by spectroscopy, single‐crystal X‐ray analysis, and chemical correlation experiments. 相似文献
992.
Chun Lei Sheng‐Xiong Huang Ji‐Jun Chen Jian‐Xin Pu Li‐Mei Li Wei‐Lie Xiao Jin‐Ping Liu Li‐Bin Yang Han‐Dong Sun 《Helvetica chimica acta》2007,90(7):1399-1405
Four new, highly oxygenated nortriterpenoids with the unique schisanartane skeleton, propindilactones A–D ( 1 – 4 ), were isolated from the aerial parts of Schisandra propinqua var. propinqua, together with four known schisanartane‐type compounds. The structures of the new plant constituents were established on the basis of extensive spectroscopic methods. 相似文献
993.
Wei‐Lie Xiao Jian‐Xin Pu Rui‐Rui Wang Liu‐Meng Yang Xiao‐Li Li Sheng‐Hong Li Rong‐Tao Li Sheng‐Xiong Huang Yong‐Tang Zheng Han‐Dong Sun 《Helvetica chimica acta》2007,90(8):1505-1513
Seven new highly oxygenated nortriterpenoids, rubriflorins D–J ( 1 – 7 ), were isolated from the leaves and stems of Schisandra rubriflora, and their structures were elucidated on the basis of extensive analysis of spectroscopic data. These new compounds feature the opening of ring A compared with related known nortriterpenoids isolated from the genus Schisandra and showed weak activity against HIV‐1. 相似文献
994.
Four new tirucallane triterpenoid saponins, named munronosides I–IV ( 2 – 5 ), along with three known triterpenoids, sapelin B ( 1 ), melianodiol, and (3β)‐22,23‐epoxytirucall‐7‐ene‐3,24,25‐triol, were isolated from the EtOH extract of the whole plants of Munronia delavayi Franch by chromatographic methods. On the basis of spectroscopic evidences, the structures of 2 – 5 were elucidated as (20S,23R,24S)‐21,25‐epoxy‐29‐{{O‐β‐d‐ glucopyranosyl‐(1→3)‐O‐[α‐l‐ rhamnopyranosyl‐(1→6)]‐β‐d‐ glucopyranosyl}oxy}‐23,24‐dihydroxytirucall‐7‐ene‐3,21‐dione ( 2 ), (3β,20S,23R,24S)‐21,25‐epoxy‐29‐{{O‐β‐d‐ glucopyranosyl‐(1→3)‐O‐[α‐l‐ rhamnopyranosyl‐(1→6)]‐β‐d‐ glucopyranosyl}oxy}‐3,23,24‐trihydroxytirucall‐7‐en‐21‐one ( 3 ), (20S,23R,24S)‐24‐(acetyloxy)‐21,25‐epoxy‐29‐{{O‐β‐d‐ glucopyranosyl‐(1→3)‐O‐[α‐l‐ rhamnopyranosyl‐(1→6)]‐β‐d‐ glucopyranosyl}oxy}‐23‐hydroxytirucall‐7‐ene‐3,21‐dione ( 4 ), and (3β,20S,23R,24S)‐24‐(acetyloxy)‐21,25‐epoxy‐29‐{{O‐β‐d‐ glucopyranosyl‐(1→3)‐O‐[α‐l‐ rhamnopyranosyl‐(1→6)]‐β‐d‐ glucopyranosyl}oxy}‐3,23‐dihydroxytirucall‐7‐en‐21‐one ( 5 ). 相似文献
995.
Hai‐Yang Liu Shi‐Jin Li Yi Zhao Wei Ni Xiao‐Jiang Hao Jun‐Zhu Li Yan Hua Bai‐Bo Xie Chen Qing Chang‐Xiang Chen 《Helvetica chimica acta》2007,90(10):2017-2023
Four new podocarpane‐type trinorditerpenenes, (5β,10α)‐12,13‐dihydroxypodocarpa‐8,11,13‐trien‐3‐one ( 1 ), (5β,10α)‐12‐hydroxy‐13‐methoxypodocarpa‐8,11,13‐trien‐3‐one ( 2 ), (5β,10α)‐13‐hydroxy‐12‐methoxypodocarpa‐8,11,13‐trien‐3‐one ( 3 ), and (3α,5β,10α)‐13‐methoxypodocarpa‐8,11,13‐triene‐3,12‐diol ( 4 ), together with four known diterpenes, 12‐hydroxy‐13‐methylpodocarpa‐8,11,13‐trien‐3‐one ( 5 ), spruceanol ( 6 ), ent‐3α‐hydroxypimara‐8(14),15‐dien‐12‐one ( 7 ), and ent‐3β,14α‐hydroxypimara‐7,9(11),15‐triene‐12‐one ( 8 ), were isolated from the twigs and leaves of Aleurites moluccana. Their structures were elucidated by means of comprehensive spectroscopic analyses, including NMR and MS. Except 8 , all compounds were evaluated for their cytotoxicity; compound 4 exhibited moderate inhibitory activity against Raji cells with an IC50 value of 4.24 μg/ml. 相似文献
996.
The addition of gem-difluorinated alkyl iodides to alkynes initiated by AIBN neatly gave the corresponding difluoromethylene vinyl iodides among which the stereoselectivity of aromatic acetylenes was high. The further coupling reaction of E-phenyl difluoromethylene vinyl iodides with terminal alkynes in the presence of catalytic palladium afforded the substituted difluorinated enynes. 相似文献
997.
A series of 1,4‐diarylquinoline derivatives were synthesized by the reaction of arylmethylidenemalononitriles or 2‐cyano‐3‐aryl‐1‐acrylate and 3‐arylamino‐5,5‐dimethylcyclohex‐2‐enone in aqueous media at 100 °C catalyzed by TEBAC. Meanwhile, the water medium was chosen as green solvent. 相似文献
998.
A series of pyrazolo[3,4‐b]pyridines was synthesized by the reaction of 5‐aminopyrazole with benzylidenemalononitrile in aqueous media. The structures were characterized by IR, 1H NMR, and elemental analysis and were further confirmed by X‐ray diffraction analysis. 相似文献
999.
Jian Wang Xing‐You Xu Lu‐De Lu Xu‐Jie Yang Wei‐Xing Ma Xiang‐Ning Cui 《Surface and interface analysis : SIA》2007,39(6):482-486
The streaming potential of supersaturated solution of binary carboxylic acids, which have even carbon atoms, was determined to characterize crystallization under different temperatures. The value of the streaming potential was related to the type and solubility of the acids and the starting temperature of crystallization, and was easily influenced by the pressure difference of the liquid or the rate of temperature decline. When the temperature was declined to the point where a crystal nucleus appeared, the streaming potential reached the minimum. Thereafter, as the temperature was sequentially lowered, some minicrystals grew, and the streaming potential presented an ascendant tendency. The higher the starting temperature of the acids saturated solution, the higher is the temperature corresponding to the streaming potential minimum. The less the carbon atoms in the acids and the greater the solubility of the acids are, the higher is the temperature of the streaming potential minimum. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
1000.
Four copper(I) cyanide coordination polymers containing 2-(n-pyridyl)benzimidazole ligands, namely [Cu2(CN)(2-PyBIm)]n (1), [Cu2(CN)2(3-PyHBIm)]n (2), {[Cu3(CN)3(4-PyHBIm)4] · 2H2O}n (3) and [Cu5(CN)3(4-PyBIm)2]n (4), have been synthesized and characterized by X-ray crystallography. Complex 1 is a one-dimension coordination polymer in which 2-(2-pyridyl)benzimidazole is deprotonated and adopts a bridging tridentate coordination mode. Complex 2 has ladder-like structure in which 2-(3-pyridyl)benzimidazole does not deprotonate and acts as a bidentate bridge. Complex 3 displays a saddle-shaped helical chain constructed through μ2-cyanide group and the outstretched neutral 2-(4-pyridyl)benzimidazole monodentate ligand. Complex 4 shows two-dimension layer polymeric structure in which deprotonated 2-(4-pyridyl)benzimidazole acts as a tridentate bridging ligand. The cyanide groups in four complexes all act as bidentate bridging ligands. These complexes are thermal stable and display luminescence in the solid states. 相似文献