- A stereodivergent approach to amino acids, amino alcohols, or oxazolidinones of high enantiomeric purity
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(-)-Menthone, an inexpensive chiral auxiliary, was used to prepare both enantiomers of α-amino acids, amino alcohols, or oxazolidinones. The sequence includes the SN2′ displacement by a cuprate reagent and a Curtius rearrangement as key steps.
- Spino, Claude,Tremblay, Marie-Claude,Gobdout, Cedrickx
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p. 2801 - 2804
(2007/10/03)
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- Method of producing optically active tert-leucinol and its use
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A method of producing optically active tert-leucinol (formula I) of high enantiomeric purity STR1 by converting racemic (RS)-tert-leucinol into a diastereomeric salt pair by reaction with an optically active acid, removing the salt pair from solution by fractionated crystallization and separating therefrom the optically active acid to release the optically active tert-leucinol from the salt. The optically active acid used is an N-acylated tert-leucine of general formula VIII: STR2 in which R can be hydrogen or an alkyl-, arylalkyl- or aryl group with up to 20 C atoms and * signifies a chirality center.
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- Chiral electrophilic 'glycinal' equivalents. New synthons for optically active α-amino acids and 4-substituted 2-oxazolidinones
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The thermal reaction of 3-[(1S)-2-alkoxy-1-apocamphanecarbonyl]-2-oxazolones (21a-c) with dialkyl azodicarboxylates (9) results in exclusive formation of [4 + 2] type cycloadducts (22 and 23) with moderate levels of diastereofacial selection (up to 72% d.e.). The diastereomers thus obtained were readily purified and subsequent treatment with acidic methanol followed by removal of the auxiliary with LiBH4/MeOH (1:2) gave optically pure 4-methoxy-5-hydrazino-2-oxazolidinones (26 and 27), which serve as α-aminoaldehyde templates useful for the synthesis of a wide variety of optically active α-amino acids as well as 4-alkyl and 4-aryl-2-oxazolidinones.
- Matsunaga, Hirofumi,Ishizuka, Tadao,Kunieda, Takehisa
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p. 1275 - 1294
(2007/10/03)
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- Synthesis of (R)-tert-Leucinol by Classical Resolution of the Racemic Mixture
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Optically active tert-leucinol is an important building block in asymmetric synthesis.However, the (R) enantiomer particularly has so far remained difficult to obtain, mainly because of the laborious synthesis of the precursor amino acid, (R)-tert-leucine.Here we present a new, classical resolution of racemic tert-leucinol, which allows straightforward preparation of each, but especially the (R) enantiomer, in good yields and high optical purities.The feasibility of the synthesis of useful derivatives is demonstrated by transformation into the corresponding (R)-4-tert-butyl-2-oxazolidinone. - Keywords: amino alcohols; asymmetric syntheses; chiral auxiliaries; enantiomeric resolution
- Drauz, Karlheinz,Jahn, Wilfried,Schwarm, Michael
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p. 538 - 540
(2007/10/03)
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- Practical Preparation of Chiral 4-Substituted 2-Oxazolidinones
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A versatile and practical route to both enantiomers of a wide variety of 4-substituted 2-oxazolidinones from the parent heterocycle is provided by regioselective substitutions via 4-methoxy derivative followed by chromatographic separation of the diastereomers derived from N-2-exo-methoxy-1-apocamphanecarbonylation.
- Ishizuka, Tadao,Kimura, Koreichi,Ishibuchi, Seigo,Kunieda, Takehisa
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p. 991 - 994
(2007/10/02)
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- Versatile routes to chiral 4-substituted 2-oxazolindinones and α-amino acids. Use of chiron, [4 + 2] cycloadducts of dialkyl azodi-carboxylates and 2-oxazolones
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The thermal reaction of 3-[(1S)-2-alkoxy-1-apocamphanecarbonyl]-2-oxazolones with dialkyl azodicarboxylates results in exclusive formation of [4 + 2] type cycloadducts with moderate levels of diastereofacial selection, which serve as versatile chiral synthons for a wide variety of 4-alkyl and 4-alkyl-2-oxazolidinones as well as α-amino acids.
- Matsunaga,Ishizuka,Marubayashi,Kunieda
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p. 1077 - 1079
(2007/10/02)
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