关键词： Modification   Genetics   Monomers   Organic compounds   Screening assays  

摘要： A strategy to restrict the highly flexible backbone conformation of a peptide nucleic acid (PNA) by incorporation of a cyclopentane ring is proposed. An asymmetric synthesis of cyclopentane-modified PNA is reported, and its binding properties were determined. The cyclopentane ring leads to a significant improvement in the binding properties of the resulting PNA to DNA and RNA.

关键词： 手性双核催化剂   不对称合成   应用   研究进展   手性双核铑配合物   手性双核钯配合物   手性双核钛配合物   铜配合物  

摘要： 综述了含相同金属的手性双核铑配合物、手性双核钯配合物、手性双核钛配合物、手性双核铜配合物等催化体系在烯烃的环丙烷化、亚胺的烯丙基化、氰硅化、缩合等不对称合成中的应用。

关键词： 联二荼   不对称合成   氧化偶联   综述  

摘要： 评述了 β 萘酚序列化合物在铜胺络合物、硫酸铜、铁盐、氧钒络合物等作用下 ,直接氧化偶联合成 1,1′ 联萘化合物的路线 ,讨论了反应机理。

关键词： eigenvalues and eigenfunctions   vibrations   Damping   Eigenvalues   damping  

摘要： This paper addresses the phenomenon of the destabilizing effect of slight damping on asymmetric linear systems. Previous works had showed that the destabilizing effect, regarded for a long time as a "paradox," depends upon the ratio of the damping coefficients. This work extends those results to n-dof systems. In fact, conditions for a general asymmetric n-dof slightly damped system to be stable are obtained. Also, a useful sufficient condition is carried out. This practical design tool gives optimum damping ratios and takes into consideration the parameter uncertainties as well. The solution is based on the eigenvalue sensitivity analysis. Moreover a formal physical explanation of the destabilizing effect of damping is given. Eventually, the theory is validated by means of a simple example.

关键词： SULFONES   AMINO compounds  

摘要： A set of diversely substituted N-Boc-gamma-amino vinyl sulfones has been prepared by a four-step procedure from readily available, highly enantiopure anti-N-Boc-3-amino-1,2-alkanediols. This new route, which does not depend on the accessibility of alpha-amino acids as starting materials, is noteworthy for its efficiency, for its generality, and for the fact that both enantiomers of a given gamma-amino vinyl sulfone can be obtained with equal ease.

关键词： PROLINE   ESTERS   DIAZO compounds  

摘要： The highly stereoselective intramolecular metal carbenoid insertion reaction of sulfinimine-derived delta-amino delta-diazoesters is used to prepare cis-5-tert-butylproline. A concerted or nearly concerted metal carbenoid N-H insertion reaction mechanism is proposed.

关键词： ENANTIOSELECTIVE catalysis   ANTIMITOTIC agents  

摘要： A catalytic asymmetric synthesis of the axially chiral bridged biaryl (-)-2, a structural analogue of natural (-)-rhazinilam possessing original antimitotic properties, is described. The key step is an intermolecular asymmetric Suzuki coupling, furnishing the nonbridged biaryl (-)-6, precursor of (-)-2, with up to 40% ee using binaphthyl ligand 7a. Various known or new binaphthyl and ferrocenyl phosphines as well as phosphetanes were screened as ligands in this reaction, the conditions of which were optimized. The comparison with another Suzuki coupling system showed that 7a is the most versatile ligand described to date for this type of transformation. This work gives the first application of the asymmetric Suzuki coupling to a biologically relevant target.

关键词： Stereoselectivity   Chemical reactions   Molecular structure   Nuclear magnetic resonance spectroscopy   Propargyls  

摘要： [GRAPHICS] The reaction of a divalent titanium reagent Ti(O-1-Pr)(4)/2i-PrMgX with optically active arylaidimines derived from arylaidehydes and O-methylphenylglycinol provided, in a highly diastereoselective manner, chiral (eta(2)-imine)Ti(O-i-Pr)(2) complexes, which in turn reacted with 1-alkynes or propargyl compounds to give optically active allyl- and alpha-allenylamines, respectively.

关键词： Hydrocarbons   Chemical reactions   Aromatic compounds   Ketones   Stereoselectivity  

摘要： Chloral or its hydrate undergoes the carbon-carbon bond-formation reaction with various optically active imines in the absence of any additive, followed by hydrolysis, to produce the corresponding beta-trichloromethyl-beta-hydroxy ketones in good yields with high enantioselectivities. In addition, the products with higher ee values were obtained by a simple recrystallization process.

关键词： 全合成   4,4\\\'\'-双异秦皮定   自偶联   交叉偶联   不对称合成   苯酞类化合物  

摘要： 为了继续利用改进的零价镍催化的Ullmann偶联反应来合成天然产物，我们首先进行了从根植物五彩凤仙花中提取出来的天然产物4，4’-双异秦皮定的首次全合成.通过11步我们以7%的总产率得到天然产物，其关键步骤是关环生成取代的4-羟基香兰素和4-香兰素对甲苯磺酸酯的镍催化偶联反应.合成了天然产物4，4’-双异秦皮定之后，我们用零价镍催化的偶联反应体系考察了4-香兰素对甲苯磺酸酯，甲磺酸酯，三氟甲磺酸酯的反应性能，然后我们优化了4-香兰素三氟甲磺酸酯的偶联反应体系，并用该体系合成了一系列的双香兰素类化合物.在得到以上结果之后，利用它们自偶联反应的速率差异我们考察了对甲苯磺酸酯，甲磺酸酯，三氟甲磺酸酯与卤代芳烃的交叉偶联反应的可能性，发现甲磺酸酯与卤代芳烃的反应结果比较好.因此我们对它们的反应体系进行了优化并用优化的反应体系进行了一系列甲磺酸酯与卤代芳烃的交叉偶联反应，其产率可以达到90%.据我们所知，用Ni（0）催化的交叉偶联的同类反应目前尚未报道.