ZnCl_2对不同类型Diels－Alder反应的催化作用

研究了ＺｎＣｌ＿２对几种不同类型的、有工业应用价值的环加成反应的催化作用。结果表明，ＺｎＣｌ＿２对具有含氧基团底物的Ｄｉｅｌｓ－Ａｌｄｅｒ反应催化效果显著。     

Wittig反应研究进展

Wittig反应是合成烯烃最为普遍的反应，该反应产率较高，条件温和，具有高度的位置选择性。综述了Wittig反应的机理、立体化学选择性以及在有机化学中的应用。     

The enhancement of stereoselectivity of a Pd-catalyzed three-component cascade reaction using parallel synthesis and multivariate analysis

Automated parallel synthesis with multivariate analysis was employed in the optimization of a Pd-catalyzed three-component cascade reaction of 7-buta-2,3-dienyl-1,3-dimethyl-3,7-dihydropurine-2,6-dione with iodobenzene and morpholine (see Scheme 1). Initially a range of reaction factors were analyzed using experimental design to optimize for selectivity, conversion, and impurity levels. Solvents and bases were screened separately as the substantial number of discrete variables involved is unsuited to the fractional factorial design used. Instead, a solvent principal component analysis (PCA) model was used in selection of solvents for screening, so gaining maximum variation in solvent properties. Similarly, tertiary amines were chosen by pKa for screening as bases alongside inorganic salts. This investigation yielded two-fold results, not only in enhancement of the reaction selectivity, but since significantly different findings were obtained on changing the solvent, the importance of the sequence of experimentation is also emphasized.     

取代基对聚丙烯茂金属催化剂立体选择性影响的分子模拟研究

利用分子模拟技术构建了丙烯单体以不同方式与茂金属催化剂活性中心配位、插入形成的π配合物和四元环过渡态的模型；计算了四元环过渡态和π配合物构象能的差。发现催化剂中取代基的大小及其所处位置会明显影响构象能的差，从而显著地影响茂金属催化剂的立体选择性。关于取代基影响茂金属催化剂立体选择性结果的阐述，将有助于人们理性地设计和开发立体选择性更加理想的茂金属催化剂。     

（R）-2-氨基-3-甲基-3-烯-丁酸甲酯的合成研究

以D-甘露醇为起始原料,经8步反应合成了具有光学活性的α-氨基酸前体-（R）-2-氨基-3-甲基-3-烯-丁酸甲酯,总收率为10．15％,e．e值为82％,其中,最具关键性和新颖性的步骤是通过Overman重排反应形成C—N键。     

Insights into Sequence–Activity Relationships amongst Baeyer–Villiger Monooxygenases as Revealed by the Intragenomic Complement of Enzymes from Rhodococcus jostii RHA1

The Rhodococcus jostii RHA1 genome encodes a number of enzymes that can be exploited as biocatalysts. Study of the substrate spectrum and enantioselectivity of Baeyer–Villiger monooxygenases from R. jostii allowed the identification of short amino acid sequences specific to groups displaying certain catalytic characteristics. The gel illustrates the substrate acceptance spectra and selectivities of the different proteins.

     

Alkynyl Group as Activating Group: Base‐Catalyzed Diastereoselective Domino Reactions of Electron‐Deficient Enynes

This paper describes a base‐catalyzed domino reaction of electron‐deficient enynes with malonate‐derived α,β‐unsaturated esters and ketones, which provides a rapid, stereoselective access to multi‐functionalized cyclopentanes and inden‐5(6 H)‐ones in high yields. In this reaction, the alkynyl group of the enyne acts as an activating group rather than a reacting group.     

Efficient Stereoselective Synthesis of Nitrocyclopropanes by the Oxidative Cyclization of Michael Adducts of Nitroolefins with Activated Methylene Compounds

An efficient oxidative cyclopropanation of the Michael adducts of nitroolefins with activated methylene compounds by the combination of iodobenzene diacetate and tetrabutylammonium iodide is reported. Highly functionalized nitrocyclopropanes are synthesized in moderate to good yields via the Michael addition and cyclopropanation with high diastereoselectivity and enantioselectivity under mild conditions.     

Palladium‐Catalyzed Allylic Alkylation of Doubly Deprotonated Carboxylic Acids

Doubly deprotonated carboxylic acids undergo smooth palladium‐catalyzed carbon alkylations with the allylic substrates methyl allyl carbonate and (E)‐methyl (pent‐3‐en‐2‐yl) carbonate to give γ,δ‐unsaturated carboxylic acids. A diastereoselective and enantioselective protocol leads to (2S,3R)‐hexenoic acid in 87% ee.     

A single active site mutation inverts stereoselectivity of 16-hydroxylation of testosterone catalyzed by engineered cytochrome P450 BM3

Inversion of stereoselectivity: screening of a minimal mutant library revealed a cytochrome P450?BM3 variant M01?A82W?S72I capable of producing 16?α-OH-testosterone. Remarkably, a single active site mutation S72I in M01?A82W inverted the stereoselectivity of hydroxylation from 16?β to 16?α. Introduction of S72I mutation in another 16?β-OH-selective variant M11?V87I, also resulted in similar inversion of stereoselectivity.