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Important Chiral Building Blocks (important + chiral_building_block)
Selected AbstractsSimple Derivatives of Natural Amino Acids as Chiral Ligands in the Catalytic Asymmetric Addition of Phenylacetylene to AldehydesEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 5 2005Zhi-jian Han Abstract Optically active propargylic alcohols are important chiral building blocks in asymmetric synthesis, and asymmetric addition of terminal alkynes to aldehydes is one of the most important and interesting procedures by which to prepare these chiral building blocks. In this work we have identified some simple derivatives of (S)-proline and other natural amino acids as chiral ligands that can be combined with Ti(OiPr)4 and then used to catalyze the asymmetric addition of zinc acetylide, produced in situ by the reaction of phenylacetylene with diethylzinc, to aldehydes. The ee value was as high as 90,%. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] Enantioselective Hydrogenation of ,-Dehydroamino Acid Esters Catalyzed by Rhodium Complexes with Chiral Bisaminophosphine LigandsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 7 2010Xianfeng Sun Abstract A highly efficient strategy for the synthesis of a series of chiral bisaminophosphine ligands was well established with several remarkable features. The synthetic utility of these ligands was explored for rhodium-catalyzed asymmetric hydrogenations of ,-dehydroamino acid esters. Up to 98% ee values were achieved for the enantioselective synthesis of aminocarboxylic acids and their derivatives, which are very important chiral building blocks for the synthesis of a variety of natural products and biologically active molecules. [source] Axial Chirality Control by 2,4-Pentanediol for the Alternative Synthesis of C3*-TunePhos Chiral Diphosphine Ligands and Their Applications in Highly Enantioselective Ruthenium-Catalyzed Hydrogenation of ,-Keto EstersADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 16 2009Xianfeng Sun Abstract A highly efficient strategy for the synthesis of a series of C3*-TunePhos chiral diphosphine ligands was well established with several remarkable features. The synthetic utility of these ligands was explored for the ruthenium-catalyzed asymmetric hydrogenation of ,-keto esters. Up to 99% ee values were achieved for the enantioselective synthesis of ,-hydroxy acid derivatives, which are very important chiral building blocks for the synthesis of a variety of natural products and biologically active molecules. [source] Primary Amine-Thioureas based on tert -Butyl Esters of Natural Amino Acids as Organocatalysts for the Michael ReactionADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 9 2009Christoforos Abstract A new class of primary amine-thioureas based on tert -butyl esters of (S)-,-amino acids and (1S,2S)-diphenylethylenediamine was synthesized and their activity as catalysts in Michael additions was evaluated. Derivatives based on di- tert -butyl aspartate and tert -butyl O - tert -butyl threoninate provided the product of the reaction between trans- ,-nitrostyrene and acetone in quantitative yield and high enantioselectivity (87,91% ee). All the thioureas based on tert -butyl esters of amino acids catalyzed the reaction of nitroolefins with acetophenone with high enantioselectivity (92,98% ee). Thus, low-cost, commercially available tert -butyl esters of natural amino acids are very important chiral building blocks for the construction of novel chiral thioureas able to catalyze asymmetric Michael additions with high enantioselectivity. [source] | ||||||||||