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991.
Peptide Deravatives as New Chiral Ligands for Enantioselective Phenylacetylene Addition to Aldehydes
ZHOU Yi-Feng GAO Yan-Feng KANG Yong-Feng HAN Zhi-Jian YAN Wen-Jin NI Ming WANG Rui 《有机化学》2004,24(Z1):162
The asymmetric addition of alkynylzinc to aldehydes is an important method of synthesizing chiral propargyl alcohols, which are important precursors to many chiral organic compounds. Recently, many significant chiral ligands in this area have been disclosed.[1] Use of a short peptide as a catalyst would allow expansion beyond the (still uncharted) repertoire of single amino acids, while conserving the advantages of a small molecule catalyst. To the best of our knowledge,no results of peptide derivatives as chiral ligands in this reaction has been disclosed to date.[2] Herein, we report the initial results of peptide derivatives, which have been used directly as a chiral ligand in this reaction (Scheme 1). 相似文献
992.
SynthesisandCharacterizationofSn┐WComplexesandCrystalStructureofPh3SnW(CO)3C5H4CH3*WANGJi-Tao**,HEHai-Yang,XUYu-Ming,ZHANGYun... 相似文献
993.
Qiong Ming XU Zhong Mei ZOU Li Zhen XU Shi Lin YANG 《中国化学快报》2005,16(10):1343-1346
Over the past two decades,the Uvaria genus has been found to be an important source of natural products with various structures and some of them have shown antitumour,antileukemic or antibiotic activities1,2.Our previous studies have resulted in the isolation of a series of polyoxygenated cyclohexenes from U.grandiflora,U.tonkinensis var.Subglabra3,4.To further search for active compounds from this genus,Uvaria kweichowensis,distributed in the southwest of China,was subjected to phytochemica… 相似文献
994.
Shi Gui ZHAO Chuan Jian ZHOU Jian Ming ZHANG Sheng Yu FENG 《中国化学快报》2005,16(10):1383-1385
Peroxide-cured high-temperature vulcanized (HTV) silicone rubber was prepared by using allyl-capped carbosilane dendrimers, in which the core molecule is Si(CHaCH=CH2)4, as the cross-linker. It showed that this kind of allyl-capped carbosilane dendrimer improved the mechanical properties of silicone rubber. 相似文献
995.
Juan Fang WU Ling Xin CHEN Guo An LUO Yong Suo LIU Yi Ming WANG Zhi Hong JIANG 《中国化学快报》2006,17(3):383-386
The advantages of berberine such as the anticancer1, antiinflammatory2 and no side effects of camptothecin1, have promoted the research in the mechanism of berberine with macrobiomolecules. In general, three different points of view have been presented on… 相似文献
996.
TheElectronicStructuresofDimericDiboroxaneandAldiminoboraneWANOZhi-zhong,XUMingandYANGZhong-zhi(IustituteofTheoreticalCliemis... 相似文献
997.
ZHANG Xiao-Mei MA Ming Wang Jian-Bo 《有机化学》2003,23(Z1):19-20
The catalytic asymmetric reactions of oxygen or sulfur ylides generated from carbenoids have attracted consider able attention in recent years. High enantioselectivities have been achieved in the 1,3-dipolar cycloaddition reactions and [ 2,3 ]-sigmatropic rearrangement of oxygen ylides. In contrast to the oxygen ylide, the corresponding catalytic asymmetric reaction of sulfur ylide is less developed. Compared to oxygen ylides, the sulfur ylides are more stable and experimental evidence supports a free ylide rather than a metal-bound ylide as reaction intermediate. That means the enantio-control must be in the step of the ylide formation. If the subsequent reaction such as [ 2,3 ]-sigmatropic rearrangement or 1,3-dipolar cycloaddition is a concerted process and is faster than the racemization of the chiral ylide intermediate, then the catalytic asymmetric sulfur ylide reaction will be possible. 相似文献
998.
A series of C2-symmetrical chiral 2,5-bis (4′-alkyloxazolin-2-yl) thiophenes (thiobox) have been synthesized from thiophene-2,5-dicarboxylic acid by sequential amidation with a chiral ethanolamine,conversion of hydroxyl to chloro group, and base-promoted oxazoline ring formation.As demonstrated by (-)-2,5-bis[4′-(S)-isopropyloxazolin-2′-yl] thiophene,these thiobox systems exhibited remarkable chirality recognition of 1,1′-bi-2-naphthol giving rise to pronounced shifts in the ^1H NMR signals of the latter axial chiral compound at the positions of C-3,C-4,C-5,and C-8. 相似文献
999.
Theoretical Study on Intermolecular Interactions and Thermodynamic Properties of Nitroamine Dimers 总被引:3,自引:0,他引:3
Ab initio self-consistent field(SCF) and Mφller-Plesset correlation correction methods employing 6-31G^** basis set have been applied to the optimizations of nitroamine dimers.The binding energies have been corrected for the basis set superposition error (BSSE) and the zero-point energy.Theree optimized dimers have been obtained.The BSSE corrected binding energy of the most stable dimer is predicted to be -31.85kJ/mol at the MP4/6-31G^**//MP2/6-31G^** level.The energy barriers of the Walden conversion for -NH2 group are 19.7kJ/mol and 18.3kJ/mol for monomer and the most stable dimer,respectively.The molecular interaction makes the internal rotation around N1-N2 even more difficult.The thermodynamic properties of nitroamine and its dimers at different temperatures have been calculated on the basis of vibrational analyses.The change of the Gibbs free energy for the aggregation from monomer to the most stable dimer at standard pressure and 298.2 K is predicted to be 14.05kJ/mol. 相似文献
1000.