Asymmetric Epoxidation of Methyl Gibberellate by the Modified Sharpless Reagent

Asymmetric epoxidation of methyl gibberellate by the modified Sharpless reagent in the various temperature is described. Compound 8 and 9 can be used as the key intermediates for synthesis of the polyhydroxygibberellins.     

Stepwise Oxidation of Ketene Dithioacetal

Ketene dithioacetals1-2 have demonstrated their potential for the synthesis of heterocycles, therefore, their synthesis and reactions have attracted much attention. The chemo- and stereo-selective conjugate addition of amine, organocuprate and Grignard reagent with ketene dithioacetal is well documented3-5, and we chose to examine whether the conjugate addition of the phosphite to the ketene dithioacetal occurs to afford the corresponding phosphonyl/S-methyl a-cyano(oxo, ethoxycarbonyl etc.) …     

Asymmetric epoxidation of gibberellates by the modified Sharpless reagent

Asymmetric epoxidation of methyl gibberellate by the modified Sharpless reagent at various temperature is described. Compound 8 and 9 can be used as the key intermediates for the syntheses of the polyhydroxygibberellins.     

Asymmetric oxidation of cyclobutanones: modification of the Sharpless catalyst

Oxidation of prochiral and racemic cyclobutanones with t-BuOOH and Ti-TADDOL-based complexes afforded lactones in up to 44% ee. The enantioselectivity of the reaction clearly depends on the amount of the reagent and the highest enantioselectivities were obtained with stoichiometric amounts of the complex. Modification of the TADDOL structure and use of the mixed complex derived from TADDOL and a tartaric ester led to more reactive but less selective oxidation systems.     

用Sharpless不对称双羟化反应合成手性β-氨基醇

以烯烃为原料合成了一组对映体纯的β-氨基醇．在手性配体1,4-双(9-O-奎宁)-2,3-二氮杂萘[(QN)₂PHAL]存在下, 通过烯烃的Sharpless不对称双羟化、环化、亲核开环和催化氢化等步骤方便地合成了手性β-氨基醇. 从环氧化物到氨基醇的总产率为89%～94%, β-叠氮醇和β-氨基醇的光学纯度高达90%～99% ee. 同时考察了影响环氧化物开环的各种因素．     

Sharpless Asymmetric Aminohydroxylation: Scope,Limitations, and Use in Synthesis

As a valuable methodology for organic synthesis , asymmetric aminohydroxylation (AA)—the catalytic and asymmetric conversion of alkenes into enantiomerically enriched N‐protected amino alcohols—has become established in a remarkably short period of time. Examples of the types of products that can be synthesized easily on a reasonably large scale and in enantiomerically pure form are shown in the picture.     

An Improved and Practical Sharpless Oxidation of Primary Alcohols to the Carboxylic Acids

An improved and practical procedure for the oxidation of primary alcohols to the carboxylic acids under Sharpless's conditions (NaIO₄/RuCl₃.H₂O/water/acetonitrile) using ethyl acetate as the solvent, in place of toxic and ecologically undesirable carbon tetrachloride, is described.     

催化量的氢化钙-硅胶对Sharpless烯丙醇不对称环氧化的影响

1980年,Sharpless发现用他的试剂[Ti-(OiPr)_4,(+)-或(-)-酒石酸和叔丁基过氧化氢]可对烯丙醇进行不对称环氧化。以后该反应广泛地应用于许多光学活性天然产物的     

生物催化硫醚底物的不对称氧化反应研究进展

综述了生物催化硫醚底物的不对称氧化反应的研究进展,重点介绍了微生物菌株整细胞、纯酶和基因工程菌等催化剂在硫醚底物的不对称氧化反应中的应用。参考文献32篇。     

Silver‐Catalyzed Asymmetric Allylation: Allyltrimethoxysilane as a Remarkable Reagent

Recently, there have been some reports on the use of allyltrimethoxysilane for enantioselective allylation with various metal fluorides or a combination of chiral complex and fluoride anion. These reactions can be applied not only to aldehydes but also to ketones and imines. In this Focus Review we discuss the development of asymmetric allylation with allyltrimethoxysilane catalyzed by chiral silver complexes.     

Highly Sensitive Determination of DAO Activity by Oxidation of a Luminescence Reagent

A highly sensitive method for measuring the activity of the enzyme diamine oxidase (DAO) independent of the type of substrate is described. The principle of the assay is to determine the amount hydrogen peroxide generated as a reaction product during oxidation of diamines by DAO. PSatto™, a highly sensitive luminescence reagent, was used to generate a signal depending on the hydrogen peroxide concentration based on the action of horseradish peroxidase. DAO is specifically captured from a sample by an antibody immobilized to microwell plates, and the substrate is added to the bound enzyme. Various diamines were used as substrates; the peroxide produced is directly proportional to the amount of DAO bound to the specific antibodies. With this very sensitive method, it is possible to detect pmol amounts of generated hydrogen peroxide in plasma matrix corresponding to the biological activity of DAO.     

Efficient Oxidation of Alcohols with Potassium Permanganate Adsorbed on Aluminum Silicate Reagent

Summary. A new reagent, potassium permanganate adsorbed on aluminum silicate, suitable for the oxidation of primary and secondary alcohols to the corresponding carbonyl compounds is described.     

Direct Oxidation of Primary tert-Butyldimethylsilyl Ethers to Carboxylic Acids with Jones Reagent

Treatment of the tert-butyldimethylsilyl ethers 1a-f with Jones reagent gave the carboxylic acids 2a-f in excellent yield in the absence of potassium fluoride.     

Efficient Oxidation of Alcohols with Potassium Permanganate Adsorbed on Aluminum Silicate Reagent

A new reagent, potassium permanganate adsorbed on aluminum silicate, suitable for the oxidation of primary and secondary alcohols to the corresponding carbonyl compounds is described.