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Chiral Amino Acids (chiral + amino_acids)
Selected AbstractsDesign and Application of 2,2-Dibromodimedone as Organic Brominating Reagent for Asymmetric Bromination of 1,3-Dicarbonyl Compounds and Ketones Catalysed by Chiral Amino AcidsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 10 2009Papori Goswami Abstract A green and ecofriendly enantioselective ,-bromination of carbonyl and 1,3-dicarbonyl compounds is reported involving the synthesis of a novel organic brominating source. The organic brominating reagent can be recovered after each cycle, rebrominated and reused. The reaction is catalysed by chiral amino acids and completed within a short reaction time with good enantioselectivity and exclusive formation of only ,-monobrominated carbonyl compounds. [source] Synthesis of Chiral Amino Acids with Metal Ion Chelating Side Chains from L-Serine Using Negishi Cross-Coupling Reaction.CHEMINFORM, Issue 24 2006Michael Kruppa 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] A solution to the observed Z, = 2 preference in the crystal structures of hydrophobic amino acidsACTA CRYSTALLOGRAPHICA SECTION B, Issue 3 2009Carl Henrik Görbitz Chiral amino acids without functional groups in their side chains (hydrophobic amino acids) systematically form crystals with two molecules in the asymmetric unit. In contrast, racemates of the same compounds form crystals with Z, = 1. The present investigation addresses the origin of this important difference between enantiomeric and racemic crystals. Through a series of ab initio calculations on infinite two-dimensional slabs, derived from crystal structures, as well as calculations on full crystal structures it is shown that it is indeed possible to explain the observed behaviour. Additionally, the (not unexpected) observation that amino acids usually form racemates in the solid phase rather than undergoing racemic separation upon crystallization is rationalized on the basis of energy calculations. [source] Design and Application of 2,2-Dibromodimedone as Organic Brominating Reagent for Asymmetric Bromination of 1,3-Dicarbonyl Compounds and Ketones Catalysed by Chiral Amino AcidsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 10 2009Papori Goswami Abstract A green and ecofriendly enantioselective ,-bromination of carbonyl and 1,3-dicarbonyl compounds is reported involving the synthesis of a novel organic brominating source. The organic brominating reagent can be recovered after each cycle, rebrominated and reused. The reaction is catalysed by chiral amino acids and completed within a short reaction time with good enantioselectivity and exclusive formation of only ,-monobrominated carbonyl compounds. [source] Chiral Induction, Memory, and Amplification in Porphyrin Homoaggregates Based on Electrostatic InteractionsCHEMPHYSCHEM, Issue 6 2009LiXi Zeng Dr. Abstract Supramolecular chirality in two configurational homoaggregates of anionic meso -tetrakis(4-sulfonatophenyl)porphyrin (TPPS) can be induced by D - and L -alanine in acidic water (see picture). The chirality can be further memorized and enforced through strong electrostatic interactions between TPPS aggregates and achiral poly(allylamine) [PAA]. Supramolecular chirality in two configurational homoaggregates of anionic meso -tetrakis(4-sulfonatophenyl)porphyrin (TPPS) can be induced by D - and L -alanine (Ala) in acidic water, respectively. The induced supramolecular chirality can be further memorized and enforced, even after complete removal of Ala or in the presence of excess Ala with the opposite configuration, through strong electrostatic interactions with achiral poly(allylamine) [PAA]. The ionic chiral interactions between TPPS and Ala or PAA are characterized by means of UV/Vis absorption and circular dichroism spectrometry. Fluorescence spectroscopy and atomic force microscopy are used as complementary techniques. On the basis of the comprehensive experimental results, a possible mechanism for chiral induction, memory, and amplification of TPPS homoaggregates by chiral amino acids and achiral PAA is proposed. Thus, we demonstrate a novel strategy to realize chiral memory in supramolecular systems by polyelectrolytes through hierarchical electrostatic self-assembly. [source] | ||||||||||