Asymmetrische Synthesen

Pracejus, H.

doi:10.1007/bfb0071301

Cited by 67 publications

(21 citation statements)

References 225 publications

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“…Cyclizations of (I) or (2) to give isoxazole derivatives have not so far been observed under these conditions.…”

Section: 5-dihydroisoxazoles From Cyclopropyl Ketone Oximes [* *I Bmentioning

confidence: 93%

“…Cyclopropyl styryl ketones ( I ) and the corresponding oximes (2) rearrange to 5,6-dihydro-4H-1,2-oxazines (3) on heating in the presence of hydroxylammonium chloride"].…”

Section: 5-dihydroisoxazoles From Cyclopropyl Ketone Oximes [* *I Bmentioning

confidence: 99%

“…We now report on the stereoselective formation of the 1phenylethyl hydratropate ester (3) from methyl(pheny1)ketene ( I ) and I-phenylethanol (2). and on the novel drastic increase in the stereoselectivity caused by addition of achiral bases such as pyridine and I ,4-diazabicycl0[2.2.2]0~tane.…”

Section: Base Catalyzed Asymmetric Induction Of the Reaction Of Methymentioning

confidence: 99%

“…(S)-( -)- (2) or rac- (2) and the base were dissolved in toluene or ether under an argon atmosphere in one limb of a (3)…”

Section: Base Catalyzed Asymmetric Induction Of the Reaction Of Methymentioning

confidence: 99%

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Base Catalyzed Asymmetric Induction of the Reaction of Methyl(phenyl)ketene with 1‐Phenylethanol: Method of Obtaining Hydratropic Acid in High Enantiomeric Purity

Jähme

Rüchardt

1981

Angew. Chem. Int. Ed. Engl.

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The conversion of (±)‐hydratropaoyl chloride into (S)‐(+)‐hydratropic acid (4) can be achieved with (S)‐(−)‐1‐phenylethanol (2) as chiral auxiliary agent in the following way: Generation of the ketene (1) from the acid chloride in situ, reaction with (S)‐(−)‐(2) in the presence of a base to give a mixture of the diastereomers (3) [with pyridine, e.g., (S,S) :(R,S) = 88 :12], hydrolysis of (S)‐(+)‐(4) with recovery of (S)‐(−)‐(2).

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“…Cyclizations of (I) or (2) to give isoxazole derivatives have not so far been observed under these conditions.…”

Section: 5-dihydroisoxazoles From Cyclopropyl Ketone Oximes [* *I Bmentioning

confidence: 93%

“…Cyclopropyl styryl ketones ( I ) and the corresponding oximes (2) rearrange to 5,6-dihydro-4H-1,2-oxazines (3) on heating in the presence of hydroxylammonium chloride"].…”

Section: 5-dihydroisoxazoles From Cyclopropyl Ketone Oximes [* *I Bmentioning

confidence: 99%

Section: Base Catalyzed Asymmetric Induction Of the Reaction Of Methymentioning

confidence: 99%

“…(S)-( -)- (2) or rac- (2) and the base were dissolved in toluene or ether under an argon atmosphere in one limb of a (3)…”

Section: Base Catalyzed Asymmetric Induction Of the Reaction Of Methymentioning

confidence: 99%

See 2 more Smart Citations

Base Catalyzed Asymmetric Induction of the Reaction of Methyl(phenyl)ketene with 1‐Phenylethanol: Method of Obtaining Hydratropic Acid in High Enantiomeric Purity

Jähme

Rüchardt

1981

Angew. Chem. Int. Ed. Engl.

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“…In 1929, Kuhn and Braun subjected racemic solutions of ethyl 2-bromopropanoate to cpl [45] to probe whether chiral photons could be used to induce chiral asymmetry into racemic organic molecules [76]. The current focus for experiments investigating cpl asymmetric photochemistry has instead been directed to amino acids due to their fundamental role in biological structure and function [1].…”

Section: Application Of Anisotropy Spectra Towards Enantioselective Pmentioning

confidence: 99%

Anisotropy Spectra for Enantiomeric Differentiation of Biomolecular Building Blocks

Evans

Meinert

Bredehöft

et al. 2013

Topics in Current Chemistry

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All biopolymers are composed of homochiral building blocks, and both D-sugars and L-amino acids uniquely constitute life on Earth. These monomers were originally enantiomerically differentiated under prebiotic conditions. Particular progress has recently been made in support of the photochemical model for this differentiation: the interaction of circularly polarized light with racemic molecules is currently thought to have been the original source for life's biological homochirality. The differential asymmetric photoreactivity of particular small molecules can be characterized by both circular dichroism and anisotropy spectroscopy. Anisotropy spectroscopy, a novel derivative of circular dichroism spectroscopy, records the anisotropy factor g = Δε/ε as a function of the wavelength. Anisotropy spectroscopy promisingly affords the wavelength-dependent determination of the enantiomeric excess (ee) inducible into chiral organic molecules by photochemical irradiation with circularly polarized light. Anisotropy spectra of small molecules therefore provide unique means for characterizing the different photochemical behaviors between enantiomers upon exposure to various wavelengths of circularly polarized light. This chapter will: (1) present the theory and configuration of anisotropy spectroscopy; (2) explain experimentally recorded anisotropy spectra of selected chiral biomolecules such as amino acids; and (3) discuss the relevance of these spectra for the investigation of the origin of the molecular homochirality observed in living organisms. This review describes a new chiroptical technique that is of significance for advances in asymmetric photochemistry and that is also highly relevant for the European Space Agency Rosetta Mission, which will determine enantiomeric excesses (ees) in chiral organic molecules in cometary ices when it lands on Comet 67P/Churyumov-Gerasimenko in November 2014.

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Absolute asymmetrische Synthese: Ursprung, Beeinflussung und Verstärkung von Chiralität

1999

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Asymmetrische Synthesen

Cited by 67 publications

References 225 publications

Base Catalyzed Asymmetric Induction of the Reaction of Methyl(phenyl)ketene with 1‐Phenylethanol: Method of Obtaining Hydratropic Acid in High Enantiomeric Purity

Base Catalyzed Asymmetric Induction of the Reaction of Methyl(phenyl)ketene with 1‐Phenylethanol: Method of Obtaining Hydratropic Acid in High Enantiomeric Purity

Anisotropy Spectra for Enantiomeric Differentiation of Biomolecular Building Blocks

Absolute asymmetrische Synthese: Ursprung, Beeinflussung und Verstärkung von Chiralität

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