关键词： Catalysts   Chemical reactions   Reaction products   Desymmetrization   Stereoselectivity  

摘要： N-Monoallylation of meso-vicinal diamine bistrisylamides using a chiral pi-allyl-Pd catalyst proceeded in an enantioselective manner (up to 90% ee) to give desymmetrization products in good yields. The product was converted to the known or-receptor agonist in short steps. In addition, the present catalytic asymmetric N-allylation was applied to kinetic resolution of racemic-diamide.

关键词： PHASE-TRANSFER CATALYSTS   CARBACEPHEM ANTIBIOTIC LORACARBEF   DYNAMIC KINETICRESOLUTION   ENANTIOSELECTIVE SYNTHESIS   SCHIFF-BASE   STEREOSELECTIVE-SYNTHESIS   ENZYMATIC-SYNTHESIS   EFFICIENT APPROACH   ALDEHYDES   DERIVATIVES  

摘要： The Cinchona alkaloid derived chiral ammonium salt developed by Park and Jew functions as an effective catalyst for the synthesis of beta-hydroxy alpha-amino acids via asymmetric aldol reactions under homogeneous conditions. The syn diastereomers are obtained in good ee, and aryl-substituted aliphatic aldehydes are the best substrates for the reaction. These results represent the highest ee's obtained to date in direct aldol reactions of glycine equivalents catalyzed by inexpensive, readily prepared chiral ammonium salts.

关键词： Reagents   Peptides and proteins   Monomers   Ketones   Enantioselective synthesis  

摘要： N-Sulfinyl alpha-amino 1,3-dithioketals are prepared in high de and good yield by treating sulfinimines with lithio-1,3-dithianes. Selective removal of the N-sulfinyl or the thioketal groups affords stable a-amino 1,3-dithioketals and N-sulfinyl alpha-amino ketones, respectively. This new sulfinimine-derived chiral building block is employed in the asymmetric synthesis of polyoxypeptin amino acid (2S,3R)-(-)-3-hydroxy-3-methylproline.

关键词： Anions   Reaction products   Stereoselectivity   Molecular structure   Allylation  

摘要： A concise method to asymmetrically synthesize 6-hydroxy-3,8-dioxabicyclo[3.2.1]octane (HDBO) derivatives was devised.

关键词： Transition states   Stereoselectivity   Mixtures   Ethers   Molecular structure  

摘要： An asymmetric synthesis of the 3,5-dihydroxycyclohexanone subunit of baconipyrones A and B, as well as that of the hydroxydiketone subunit of baconipyrones C and D ((-)-(4S,6S)-4,6-dimethyl-5-hydroxynonan-3,7-dione), is described. Key steps include sulfur dioxide-induced additions of enoxysilanes to 1,3-dioxy-1,3-dienes, followed by retro-ene desulfitations (retro-ene elimination of SO2).

关键词： Hydrocarbons   High-performance liquid chromatography   Ligands   Aromatic compounds   Hydrogenation  

摘要： A facile preparation of chiral alpha-aryloxy carboxylic acids via asymmetric hydrogenation of the corresponding unsaturated acids has been discovered. A number of catalysts have been identified that give high product enantioselectivity, and the scope of the reaction has been examined with respect to substitution on the aromatic ring and olefin.

关键词： DNA分子荧光探针   三维有序大孔材料   胶晶模板法   制备   生物催化去消旋化   不对称合成   硫酸钡   结晶动力学   湿法磷酸   Heck反应   负载型钯催化剂  

关键词： fluorine and compounds   asymmetric synthesis   amino aldehydes   amino acids   oxidation  

摘要： Asymmetric synthesis of beta-trifluoromethylated beta-amino aldehyde and acid derivatives via the oxidation of enantiopure alpha-trifluoromethylated homoatlylamine as a new trifluoromethylated chiral building block is described. (C) 2004 Elsevier B.V. All rights reserved.

关键词： SPARTEINE   MYOCARDIAL depressants   ASYMMETRIC synthesis   ASYMMETRY (Chemistry)   ORGANIC synthesis (Chemistry)   ORGANIC chemistry  

摘要： Three new (+)-sparteine-like diamines were prepared from (-)-cytisine and evaluated as sparteine surrogates in the alpha-lithiation rearrangement of cyclooctene oxide and the palladium(II)/diamine catalyzed oxidative kinetic resolution of I-indanol. The new diamines exhibited opposite enantioselectivity to that observed with (-)-sparteine but increasing the steric hindrance of the N-alkyl group beyond N-Et had a detrimental effect on enantioselectivity. The optimal N-Me diamine was evaluated with much success in five other (-)-sparteine-mediated processes involving different metals (lithium, magnesium, and copper) and different types of reaction mechanisms.

关键词： ORGANOSULFUR compounds   ORGANIC synthesis (Chemistry)   CYCLIC compounds   RING formation (Chemistry)   CHIRALITY   OXIDATION  

摘要： A novel and efficient enantioselective synthesis of both enantiomers of syn-(3-trifluoromethyl)isoserine was achieved. Ring opening of trifluoromethylated cyclic sulfates 3, derived from enantiopure trifluoromethylated vicinal diols 2, with various nucleophiles occurred exclusively at C2 with inversion of chirality. Treatment of 4c and 4d, obtained by nucleophilic opening of 3a and 3b with PhCO2NH4, with (CF3SO2)(2)O followed by substitution with sodium azide, Jones oxidation, and hydrogenolysis furnished (2S,3S)-(N-benzoyl)-3-(trifluoromethyl)isoserine 9a and (2R,3R)-(N-benzoyl)-3-(trifluoromethyl)isoserine 9b, respectively.