关键词： enantioselective amination   reductive transamination   enantioselective hydrogenation   Schiff base   2-butanamine   methoxyisopropylamine   chiral modifiers   methylethylketone   methoxyacetone   palladium catalyst   conformational analysis  

摘要： Methylethylketone (MEK) and methoxyacetone (MEOAC) were transaminated with benzylamine (BzNH(2)) or L-(-)-alpha-methylbenzylamine [L-(-)-alpha-MeBzNH(2)] over Pd/C catalysts in the presence of chiral modifiers (L-alanine, L-alaninol, L-phenylalaninol, L-lysine and methyl-, t-butyl- and benzyl-esters of L-alanine) introduced either by incipient wetness impregnation or by equilibrated impregnation onto the catalyst surface. In the first step of the transamination the Schiff base was formed from the ketone and aralkylamine which was then hydrogenated to secondary amine in the second step. In the third step of the transamination the hydrogenolysis of the secondary amine resulting in primary alkylamine and a hydrocarbon was carried out. In the transamination of both MEK and MEOAC on Pd/C catalysts the highest enantiomeric excess was observed in cyclohexane (ee = -20%-21%) using L-alanine alkyl esters or L-alaninol as modifier. In different solvents the ee of the corresponding primary amine increased in the order: MeOH < Dioxan < H2O < CH. Upon using (L)-(-)-alpha-MeBzNH(2), as a chiral transaminating agent, (S)-methoxyisopropylamine was obtained, with ee value around 70%. The conformational analysis of N-(methoxy-2-propylidene)-methylbenzylamine strongly supports the validity of Prelog's rule in the enantio- or diastereoselective hydrogenation of Schiff base over heterogeneous catalysts. (C) 1999 Elsevier Science B.V. All rights reserved.

关键词： 萘普生   不对称合成   缩酮   水解   重排   消炎镇痛药  

摘要： 改进了萘普生的Ｚａｍ ｂｏｎ 法不对称合成工艺。缩酮制备时，采用甲苯为共沸剂；α－溴代缩酮以相转移催化水解并简化重排反应。总产率达４５．４％ 。

摘要： The crystal structure of a cyclic sulfoximine, 2-amino-4-(4-ethyl-1,3-dioxo-4,5-dihydra-1,2-thiazol-1-yl)butanoic acid, C9H16N2O4S, was determined to ascertain its stereochemistry. The absolute configuration of the chiral S atom was S on the basis of the (S)-alpha-carbon derived from the synthetic precursor, L-homocysteine.

关键词： Mixtures   Enolates   Carbene complexes   Organic compounds   Reaction products  

摘要： The reaction of lithium enolates of achiral N-protected glycine esters with chiral alkoxyalkenylcarbene complexes of chromium provided the corresponding Michael adducts with either high anti or syn selectivity depending on the nature of the nitrogen protecting group, ana high diastereofacial selectivity when carbene complexes containing the (-)-8-phenylmenthyloxy group were employed. Subsequent oxidation of the metal-carbene moiety followed by deprotection of the amine group and hydrolysis of both carboxylic esters afforded enantiomerically enriched 3-substituted glutamic acids of natural as well as unnatural stereochemistry. Alternatively, when the deprotection seep was performed previously to the oxidation, cyclic aminocarbene complexes were formed, which finally led to optically active 3-substituted pyroglutamic acids.

关键词： Hydrocarbons   Reaction products   Catalysts   Aromatic compounds   Hydrogenation  

摘要： No abstract available

关键词： Antimicrobial agents   Aldehydes   Ketones   Molecular structure   Aldol reactions  

摘要： Antimalarial alkaloids febrifugine (1) and isofebrifugine (2) were efficiently synthesized from simple achiral starting materials on the basis of the catalytic asymmetric synthesis. The first key reaction was performed using the tin(II)-mediated catalytic asymmetric aldol protocol to afford chiral aldehyde 3 in high yield with high diastereo- and enantioselectivities. The second key step, a Mannich-type reaction, did not give satisfactory results according to the conventional methods. We then developed a novel aqueous Mannich-type three-component reaction of an aldehyde, an amine, and a vinyl ether using a Lewis acid-surfactant combined catalyst (LASC), and the key intermediates 16 and 17 were obtained in high yields. The final coupling reactions of bromoacetone 14 with 4-hydroxyquinazoline were carried out using basic conditions, and successive deprotection gave 1 and 2, respectively, without any isomerization. These unambiguous total asymmetric syntheses revealed that the absolute configurations of febrifugine and isofebrifugine were not (2'S,3'R) and (2'R,3'R) as reported previously but (2'R,3'S) and (2'S,3'S), respectively (1' and 2'). Finally, antimalarial activities of the synthesized febrifugine and isofebrifugine, and their antipodes, were examined. It was revealed that the activities and selectivities of natural febrifugine and isofebrifugine were much higher than those of the antipodes.

关键词： Ethers   Nitrogen compounds   Chromatography   Fluorine   Enantioselective synthesis  

摘要： No abstract available

关键词： 光学活性   吡咯烷酮   不对称合成   果酸  

摘要： 鉴于光学活性吡咯烷酮在生理活性化合物及不对称合成中的重要性,该论文的目的在于发展光学活性2-吡咯烷酮Ⅰ的新合成方法以及研究新的光学活性手性吡咯烷酮有主其不对称合成方法,以期为今后发展新的手性辅助剂提供候选化合物.首先,从(S)-苹果酸出发,合成了苯砜Ⅲ.通过以苯砜基作为离去基团,建立了一条新的不对称酰胺α-烷基化合成Ⅳ的方法.其次,从外消旋的苹果酸出发,合成了酰亚胺(±)-Ⅴ.通过还原烷基化方法合成了(±)-Ⅳ,产率为95%.通过高效液相色谱用手性柱对(±)-Ⅳ进行拆分以及与(±)-Ⅳ对照,可确定(±)-Ⅳ的e.e值大于95%.表明了从(S)-苹果酸出发,通过该法合成(+)-Ⅳ,未观察到明显的外消旋化.再次,从价廉的内型降冰片烯酸酐Ⅱ出发合成了化合物Ⅵ,对其N-α还原烷基化反应进行了初步研究,合成了化合物Ⅶ,为发展新型的手性辅助基奠定了基础.最后,从琥珀酐出发,合成了氮上带有手性诱导基的吡咯烷酮Ⅷ,并对其不对称还原烷基化进行进行了初步的研究,积累了一定的经验.

关键词： 萘普生   不对称催化   不对称合成  

摘要： 按反应类型介绍了近几年来催化不对称合成非甾体消炎镇痛药萘普生的各种新方法。

关键词： 脂肪酶   光学活性农药   不对称合成   催化   合成  

摘要： 脂肪酶作为天然的手性催化剂，具有高立体选择性、作用底物广泛、催化反应条件温和的特点，在不对称合成、光学活性化合物及天然产物的合成领域具有广泛的用途。