- Molecular recognition on crystallization of enantiopure and racemic N-benzoylalanine methyl ester
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The melting points of crystals of (S)- and (RS)-N-benzoylalanine methyl ester derived from solutions of ethyl acetate/light petroleum are 56-57.5° and 81.5-82.5°, respectively, reflecting differences in lattice energy that are apparent from the crystal structures. A more extensive mode of association between chains, uniformly stabilized by N-H?O=C interactions, is found in the racemate leading to a more efficient packing of molecules. The higher lattice energy of the racemate has been confirmed through the enantiomeric enrichment of an optically active sample and the partial resolution of (RS)-N-benzoyl(2-2H)alanine methyl ester, through molecular recognition on crystallization. CSIRO 2000.
- Coghlan, Daniel R.,Easton, Christopher J.,Tiekink, Edward R. T.
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- Simple and efficient preparation of (R)- and (S)-enantiomers of α-carbon deuterium-labelled α-amino acids
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A procedure for the synthesis of (R)- and (S)-enantiomers of α-carbon deuterium-labelled α-amino acids, exemplified for (R)- and (S)-[2-2H1]-Leu is described. Starting from the respective (S)- or (R)-enantiomer or from the racemic mixture of an α-amino acid the selective proton exchange at the α-carbon is carried out by racemization via a Schiff base in monodeuterated acetic acid as solvent which serves as deuterium source. After N-protection the racemic mixture is liquid chromatographically separated into the individual (R)- and (S)-enantiomers on preparative scale employing a chiral anion exchanger based on carbamoylated quinine as chiral selector. After deprotection the enantiomerically pure products can be obtained in good yields.
- Mitulovi, Goran,Laemmerhofer, Michael,Maier,Lindner, Wolfgang
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p. 449 - 461
(2007/10/03)
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