关键词： Hydrocarbons   Anions   Cyclopropanation   Molecular structure   Vinyl  

摘要： [GRAPHICS] The callipeltoside A chlorocyclopropyl-containing dienyne side chain has been synthesized in nine steps and 33% overall yield from commercially available 1,2,5,6-O-dicyclohexylidene-D-mannitol. The key steps in the synthesis are a highly diastereoselective cyclopropanation of a vinyl chloride allylic ether and a Suzuki cross-coupling to complete the carbon framework.

关键词： (S)-异丝氨酸   不对称合成  

摘要： (S) -异丝氨酸是一种具有生物活性的 β-氨基酸和重要的医药中间体。本文重点介绍了以手性化合物为原料合成 ( S) -异丝氨酸的路线 ,并对 ( S) -异丝氨酸的不对称合成路线进行了系统阐述。

关键词： BINAP   金属配合物   不对称合成   催化剂   烯烃   酮   亚胺   结构   不对称氢化   关环反应  

摘要： 综述了BINAP金属配合物催化剂在烯烃、酮、亚胺的不对称氢化以及在关环反应、C-C键形成反应等中的应用.

关键词： L-苯丙氨酸   氨基酸   不对称合成   发酵法   酶法  

摘要： 对目前国内外L 苯丙氨酸制备方法的研究进展进行了综述 ,并介绍了L 苯丙氨酸不对称合成的最新研究进展。

关键词： α-氨基膦酸   α-氨基膦酸酯   催化不对称合成   化学计量不对称合成   光学活性  

摘要： 综述了近年来光学活性 α-氨基膦酸及其酯的各种不对称合成方法 ,包括化学计量不对称合成和催化不对称合成。重点介绍了近年发展起来的催化不对称合成方法 ,并且对各种合成方法的优劣进行了评述。

关键词： .Lewis acids   stereocontrol   Diels–Alder   asymmetric synthesis   dienophiles   pinacol   high diastereofacial   extremely high   ketoamides  

摘要： Diels-Alder cycloadditions of S-indoline chiral acrylamides with cyclopentadiene in the presence of Lewis acids proceed with high diastereofacial selectivity, giving either endo-R or endo-S products depending on Lewis acid and the structures of chiral dienophiles. Diastereo- and enantioselective pinacol coupling reactions of chiral alpha -ketoamides mediated by samarium diiodide afforded extremely high diastereoselectivities. Enantiopure (S,S)- or (R,R)-2,3-dialkyltartaric acid and derivatives can be synthesized. Furthermore, it was demonstrated that alpha,beta -unsaturated amides coupled with SmI2 to dimerized products containing two chiral carbons which were first obtained as the adjacent chiral carbons.

关键词： asymmetric   chiral imide   enantioselective   fatty acid   hydroxylation   oleic acid   oxazolidinone  

摘要： Highly selective asymmetric synthesis of 2-hydroxy fatty acid methyl esters has been accomplished through chiral imide enolates. Five chiral oleic acid imides were prepared by reaction of oleic acid with pivaloyl chloride followed by reaction with five different lithiated chiral oxazolidinones including (R)-(+)-4-benzyl-2-, (S)-(-)-4-benzyl-2-, (4R,5S)-(+)-4-methyl-5-phenyl-2-, (4S,5R) -(-)-4-methyl-5-phenyl-2-, and (R)(+)-4-isopropyl-2-oxazolidinones in 88-92% yields. The chiral imides were reacted with NaN(Mq(3)i)(2) at -78 degreesC to give enolates, which subsequently reacted with 2-(phenylsulfonyl)-3-phenyloxaziridine to give hydroxylated products in 78-83% yields. Methanolysis of the hydroxylated products with magnesium methoxide gave methyl 2-hydroxyoleate. Enantiomeric excesses tee) of the products were determined to be very high (98-99% eel by H-1 nuclear magnetic resonance study after esterification of the hydroxy group with (S)-(+)-O-acetylmandelic acid. Enantioselective hydroxylation of other fatty acids including elaidic, petroselinic, vaccenic, and linoleic was evaluated under the similar conditions using (4R,5S)-(+)-4-methyl-5-phenyl-2-oxazolidinone as a chiral auxiliary to give 98% ee values for all cases.

关键词： .optically active   salen   asymmetric synthesis   BINOL   privileged ligands  

摘要： Different types of chiral "privileged" ligands 1 and 2 in promoting enantioselective addition of allylating agents to aliphatic and aromatic aldehydes;are described. Here, a new concept in the asymmetric allylation reaction is presented. Redox [Cr(Salen)] mediated addition of allyl halides to carbonyl compounds is described, and mechanistic investigations are discussed. These results open access to the fascinating area of the catalytic redox processes mediated by metallo-Salen complexes.

关键词： .highly enantioselective   halide ions   optically   hydride elimination   II Catalyzed   alkynoates   active butyrolactones  

摘要： In the palladium(II)-catalyzed enyne coupling reactions, the nitrogen-containing ligand plays the same role as the halide ion to inhibit the beta -hydride elimination. Employing the pymox or bisoxazoline as ligands, the catalytic asymmetric cyclization of (Z)-4'-acetoxy-2'-butenyl 2-alkynoates initiated by acetoxypalladation was established with high efficiency (up to 92% ee) to afford the optically active gamma -butyrolactones.

关键词： STEREOCHEMICAL ANALYSIS   Activation entropy   deceleration   Reagents   tethers  

摘要： [GRAPHICS] Kinetic measurements to determine effective molarities of intramolecular reactions using 2,4-pentanediol and related tethers showed that methyl groups on the tether accelerate the major diastereomeric process but decelerate the minor process. The efficient promotion of stereocontrol is suggested to be due to chiral perturbation of the reaction rate through the entropy term, The conformation of the encounter complex of the reagent and reactant moieties was deduced by stereochemical analysis of the intramolecular adducts.