Racemic and (+)-ethyl 2-acetamido-2-carboxy-5-oxohexanoate
作者： Daniel A. Osborne , W. Reid Dreher, Jr. , H. Ray Gore, Jr. , Andrew Stoddard , Edward J. Valente
关键词: Carboxylic acid 、 Ketone 、 Stereochemistry 、 Diastereomer 、 Enantiomer 、 Chemistry 、 Amide 、 Molecule 、 Hydrogen bond 、 Hydrolysis
摘要: Racemic ethyl 2-acetamido-2-carboxy-5-oxohexanoate has been isolated by single hydrolysis of the corresponding diethyl ester and resolved essentially quantitatively diastereomeric salt formation with (−)-quinine. The (+)-isomer was retrieved from less-soluble quininium salt. Racemate crystals, (plusmn;)-1, are monoclinic, space group P21/c, a = 7.609(4)A, b 16.731(7)A, c 10.746(5) A, β 99.83(4)° enantiomeric (+)-1, P21, 5.857(2)A, 15.282(4)A, 7.618(2)A, 95.62(2)°. Molecular packing is similar in two structures; enantiomer 0.7% higher volume per molecule lower fusion temperatures 3°C. In both structures, carboxylic acids donate hydrogen bonds to amide carbonyls adjacent molecules without reciprocation. Amides form three-centered carboxy oxygen an intramolecular acid ketone carbonyl molecule.
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