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Chiral Amplification (chiral + amplification)
Selected AbstractsHighly Enantioselective Conjugate Addition of Thioglycolate to Chalcones Catalyzed by Lanthanum: Low Catalyst Loading and Remarkable Chiral Amplification,ANGEWANDTE CHEMIE, Issue 25 2010Yonghai Hui Kleineree,große Wirkung: Mit dem Lanthan(III)-Komplex eines chiralen N,N,-Dioxids als Katalysator verlief die Titelreaktion hoch enantioselektiv und mit hohen Ausbeuten. Besonders bemerkenswert war die große asymmetrische Verstärkung: Das Produkt wurde mit 98,%,ee erhalten, wenn 1,Mol-% L/La(OTf)3 mit 2,%,ee für L eingesetzt wurde. Tf=Trifluormethansulfonyl. [source] Chiral Amplification Based on Enantioselective Dual-Phase Distribution of a Scalemic Bisoxazolidine Catalyst.CHEMINFORM, Issue 48 2007Shuanglong Liu Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] Synthesis and chiroptical properties of optically active poly(ethynylcarbazole) derivatives: Substituent effect on the helix formationJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 19 2007Fumio Sanda Abstract Novel chiral acetylene monomers containing carbazole, 2-ethynyl-9-[(S)-2-methylbutoxycarbonyl]carbazole (1), 3-ethynyl-9-[(S)-2-methylbutoxycarbonyl]carbazole (2), 2-ethynyl-9-[(S)-2-methylbutyl]carbazole (3), and 2-ethynyl-9-[(S)-4-methylhexyl]carbazole (4) were synthesized and polymerized with [(nbd)RhCl]2Et3N. The corresponding polyacetylenes with number-average molecular weights ranging from 68,700 to 310,000 were obtained in good yields. Poly(1) exhibited a large specific rotation and an intense Cotton effect in toluene, indicating that it formed a helix with predominantly one-handed screw sense, while the other three polymers showed no evidence for taking a helical structure. Poly(1) largely decreased the CD intensity upon heating from ,10 to 60 °C. Poly(1) showed a Cotton effect in film state in a manner similar to solution state. No chiral amplification was observed in the copolymerization of 1 with achiral 2-ethynyl-9- tert -butoxycarbonylcarbazole (5). © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4450,4458, 2007 [source] Enantiorecognition on solid chiral selectors using microbatch technology: an example of limitation in case of strong association in the racemateBIOMEDICAL CHROMATOGRAPHY, Issue 6 2005Christian Roussel Abstract When they were independently tested, the enantiomers of N,N,-bis(salicylidene)- trans -1,2-cyclohexanediamine showed a large difference in adsorption on new chiral selectors using microbatch technology. Surprisingly, when these enantiomers were applied on the same supports as a racemic mixture, no discrimination was observed even though suitable adsorption existed. When a mixture enriched in one enantiomer (scalemic mixture) was applied, the resulting supernatant contained the racemic form and the enantiomer in excess was adsorbed on the support together with a part of racemate. This behavior, which militates in favor of a strong heterochiral dimer formation in the racemate, was revealed using microbatch technology but remained hidden on classical column chromatography on chiral support. Molecular dynamics calculations corroborate this hypothesis, showing a favorite binding mode of the heterochiral dimer, which is stabilized by various inter- and intramolecular interactions. Our findings may be considered as a new limitation of microbatch technology, but they may have some inference in case of chiral amplification using the N,N,-bis(salicylidene)- trans -1,2-cyclohexanediamine enantiomers as chiral ligands. Copyright © 2005 John Wiley & Sons, Ltd. [source] | ||||||||||