Method for the racemization of optically active amino acids

Yamada, Shigeki; Hongo, Chikara; Yoshioka, Ryuzo; Chibata, Ichiro

doi:10.1021/jo00154a019

Cited by 145 publications

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“…Enantiomerically pure (S,S,S)-1 was then submitted to Yamada's epimerization procedure, 15 by heating in acetic acid in the presence of a catalytic amount of salicylaldehyde to promote the formation of a Schiff base (Scheme 2). According to the literature, 12a the epimerization progresses to give a 50:50 mixture of diastereoisomers after 1 hour.…”

Section: Resultsmentioning

confidence: 99%

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Versatile methodology for the synthesis and α-functionalization of (2R,3aS,7aS)-octahydroindole-2-carboxylic acid

et al. 2008

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An improved strategy for the effective synthesis of enantiomerically pure (2R,3aS,7aS)-octahydroindole-2-carboxylic acid (Oic), based on the formation of a trichloromethyloxazolidinone derivative, has been developed. Additionally, the completely diastereoselective α-alkylation of such oxazolidinone provides a very convenient and concise route to enantiopure α-tetrasubstituted derivatives of this Oic stereoisomer.

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Section: Resultsmentioning

confidence: 99%

“…After 24 h, the catalyst was filtered off and washed with acetic acid. The solvent was evaporated to dryness and the resulting residue was crystallized from ethanol to afford pure (S,S,S)-1 as a white solid (2.64 g, 15 …”

Section: Synthesis Of (2s3as7as)-octahydroindole-2-carboxylic Acidmentioning

confidence: 99%

Versatile methodology for the synthesis and α-functionalization of (2R,3aS,7aS)-octahydroindole-2-carboxylic acid

et al. 2008

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“…For the role that crystallization plays in chiral separation, see : Blackmond & Klussmann (2007); Blackmond et al (2008). For the role of the H atom on the -C atom in enhancing the rate of racemization, see: Yamada et al (1983). For the mechanism of racemization of amino acids lacking an -H atom, see : Pizzarello & Groy (2011).…”

Section: Related Literaturementioning

confidence: 99%

“…Another important aspect in the prebiotic chemistry of the amino acids is the role of racemization. All of the nineteen naturally occurring chiral amino acids have a hydrogen atom on the alpha carbon atom, which enhances the rate of racemization (Yamada et al, 1983).…”

Section: S1 Commentmentioning

confidence: 99%

2-Methylaspartic acid monohydrate

et al. 2013

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Key indicators: single-crystal X-ray study; T = 123 K; mean (C-C) = 0.006 Å; R factor = 0.090; wR factor = 0.279; data-to-parameter ratio = 12.2.The title compound, C 5 H 9 NO 4 ÁH 2 O, is an isomer of theamino acid glutamic acid that crystallizes from water in its zwitterionic form as a monohydrate. It is not one of the 20 proteinogenic -amino acids that are used in living systems and differs from the natural amino acids in that it has anmethyl group rather than an -H atom. In the crystal, an O-HÁ Á ÁO hydrogen bond is present between the acid and water molecules while extensive N-HÁ Á ÁO and O-HÁ Á ÁO hydrogen bonds link the components into a three-dimensional array.

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“…In general, optically active { { a-amino acids undergo racemization with carbonyl compounds, such as salicylaldehyde, which acts as a catalyst in acetic acid. 9) Therefore, epimerization at the C-2 position of threonine (Thr) will yield a diastereoisomeric mixture of Thr and aThr. However, Thr and aThr are difficult to separate from the mixture without transformation into their derivatives, such as O-methyl-N-acyl derivatives.…”

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Preparation of Optically Active Allothreonine via Optical Resolution by Replacing Crystallization.

Shiraiwa

Fukuda

Kubo

2002

CHEMICAL & PHARMACEUTICAL BULLETIN

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D-and L-Allothreonine [D-and L-aThr; (2R,3R)-and (2S,3S)-2-amino-3-hydroxybutanoic acid] are useful as chiral reagents in asymmetric syntheses.1) However, D-and L-aThr, non-proteinogenic a-amino acids, are difficult to produce commercially in large quantities. Therefore, synthetic DLaThr 2-4) has been subjected to optical resolution by separating the diastereoisomeric salts of DL-aThr derivatives to obtain the enantiomers. 5,6) In our previous paper, 7) DL-aThr was found to exist as a conglomerate and to be optically resolved by preferential crystallization and replacing crystallization of DL-aThr. The optical resolution by replacing crystallization is a procedure for obtaining an enantiomer from a conglomerate, and is achieved by allowing an optically active co-solute to coexist in a racemic supersaturated solution.8) DL-aThr was optically resolved using 4-hydroxy-L-proline (L-Hyp) as the optically active cosolute, and D-aThr was allowed to preferentially crystallize from a supersaturated solution of DL-aThr.7) Although L-aThr will be preferentially crystallized from the racemic solution in the presence of D-Hyp, L-Hyp is expensive and D-Hyp is not commercially available. Therefore, we selected D-and L-Ala, which are commercially available and are the most inexpensive optically active a-amino acids, as the optically active cosolutes in optical resolution by replacing crystallization of DL-aThr (Chart 1).Optical resolution by replacing crystallization is based on different interactions between enantiomers and the optically active co-solute. Therefore, the solubilities (mole fractions) of D-, L-, and DL-aThr were first measured in the presence of L-Ala (16.0 mmol) in 100 cm 3 of water at 10°C; these values are summarized in Table 1

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Method for the racemization of optically active amino acids

Cited by 145 publications

References 0 publications

Versatile methodology for the synthesis and α-functionalization of (2R,3aS,7aS)-octahydroindole-2-carboxylic acid

Versatile methodology for the synthesis and α-functionalization of (2R,3aS,7aS)-octahydroindole-2-carboxylic acid

2-Methylaspartic acid monohydrate

Preparation of Optically Active Allothreonine via Optical Resolution by Replacing Crystallization.

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