نتایج جستجو برای: asymmetric transformation
تعداد نتایج: 285010 فیلتر نتایج به سال:
Three short-chain alcohol dehydrogenases from Burkholderia gladioli were discovered for their great potential in the dynamic kinetic asymmetric transformation of methyl 2-benzamido-methyl-3-oxobutanoate, and their screening against varied organic solvents and substrates. This is the first report of recombinant enzymes capable of achieving this reaction with the highest enantio- and diastereo-se...
An enantioselective dearomatization of isoquinolines has been developed using chiral anion-binding catalysis. This transformation, catalyzed by a simple and easy to prepare tert-leucine-based thiourea derivative, makes use of silyl phosphite as a nucleophile and generates cyclic α-aminophosphonates. This is the first time asymmetric anion-binding catalysis has been applied to the synthesis of α...
Readily prepared 2-alkyl-2-azidopropylcycloalkyl-1,3-diones undergo intramolecular Schmidt rearrangement with a range of hard Lewis acids, leading to indolizidinediones and pyrroloazepinediones. Chiral aluminium-based Lewis acids could also be used to mediate this symmetry-breaking transformation, but no significant asymmetric induction was observed.
A microscopic model for a solid-on-solid type of interface under the influence of an external field is introduced. It is proven that in equilibrium the macroscopic profile satisfies a partial differential equation which is (up to a transformation) the stationary Burgers equation. The study is based on the structure of the invariant measures for a related asymmetric simple exclusion process.
We investigate symmetry-breaking bifurcation patterns in evolution in the framework of adaptive dynamics (AD). We define weak and strong symmetry. The former applies for populations where only the simultaneous reflection of all individuals is an invariant transformation. The symmetry is strong in populations where reflection of some, but not all, individuals leaves the situation unchanged. We s...
The anomalies of a very general class of non local Dirac operators are computed using the ζ-function definition of the fermionic determinant and an asymmetric version of the Wigner transformation. For the axial anomaly all new terms introduced by the non locality can be brought to the standard minimal Bardeen’s form. Some extensions of the present techniques are also commented.
Asymmetric synthesis of the sulfide lactones 12 and 13 in excellent enantiopurity is achieved by reduction of cyclohexanone derivative 10 using baker’s yeast, followed by acid catalysed cyclisation. The outcome of the yeast reduction is very sensitive to the reaction conditions employed. Transformation of 12 to the α-diazosulfoxide 4 (≥98%ee) and rhodium acetate catalysed decomposition of this ...
A mild catalytic asymmetric direct fluoro-arylation of styrenes has been developed. The palladium-catalyzed three-component coupling of Selectfluor, a styrene and a boronic acid, provides chiral monofluorinated compounds in good yield and in high enantiomeric excess. A mechanism proceeding through a Pd(IV)-fluoride intermediate is proposed for the transformation and synthesis of an sp(3) C-F bond.
This account describes our laboratory's efforts in the development of a palladium-catalyzed asymmetric conjugate addition of arylboronic acids to cyclic conjugate acceptors. Specifically, we highlight the study of this transformation in the following areas: (a) construction of all-carbon quaternary stereocenters, (b) elucidation of the reaction mechanism,
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