High-performance liquid chromatographic enantioseparation of unusual amino acid derivatives with axial chirality on polysaccharide-based chiral stationary phases.
The successful enantioseparation of axially chiral amino acid derivatives containing a cyclohexylidene moiety on an analytical and semipreparative scale was achieved for the first time by HPLC using polysaccharide-based chiral stationary phases. Racemic methyl N-benzoylamino esters, easily obtained by methanolysis of the corresponding 5(4H)-oxazolones, were subjected to chiral HPLC resolution using chiral stationary phases based on immobilized 3,5-dimethylphenylcarbamate derivatives of amylose (Chiralpak(®) IA column) or cellulose (Chiralpak(®) IB column). The behaviour of both selectors under different elution conditions was evaluated and compared. The amylose column showed better performance than the cellulose column for all enantiomers tested. The semipreparative resolution of axially chiral amino acid derivatives with different side chains has been achieved on a 250mm×20mm ID Chiralpak(®) IA column using the appropriate mixture of n-hexane/chlorofom/ethanol as eluent by successive injections of a solution of the sample in chloroform. Using this protocol up to 120mg of each enantiomer of the corresponding axially chiral amino acid derivative were obtained from 300mg of racemate. [(Sa)-2a, 105mg; (Ra)-2a, 60mg, [(Sa)-2b, 105mg; (Ra)-2b, 90mg, [(Sa)-2c, 120mg; (Ra)-2c, 100mg].
Departamento de Catálisis y Procesos Catalíticos, Instituto de Síntesis Química y Catálisis Homogénea (ISQCH), CSIC-Universidad de Zaragoza, c/Pedro Cerbuna 12, E-50009 Zaragoza, Spain. Electronic address: pilopez@unizar.es.
Pilar
P
López-Ram-de-Víu
Departamento de Catálisis y Procesos Catalíticos, Instituto de Síntesis Química y Catálisis Homogénea (ISQCH), CSIC-Universidad de Zaragoza, c/Pedro Cerbuna 12, E-50009 Zaragoza, Spain.
José A
JA
Gálvez
Departamento de Catálisis y Procesos Catalíticos, Instituto de Síntesis Química y Catálisis Homogénea (ISQCH), CSIC-Universidad de Zaragoza, c/Pedro Cerbuna 12, E-50009 Zaragoza, Spain.
María D
MD
Díaz-de-Villegas
D000596:Amino Acids / Q000302:isolation & purification*; D000688:Amylose / Q000031:analogs & derivatives / Q000737:chemistry; D002482:Cellulose / Q000031:analogs & derivatives / Q000737:chemistry; D002851:Chromatography, High Pressure Liquid; D004952:Esters; D048448:Phenylcarbamates / Q000737:chemistry; D011134:Polysaccharides / Q000737:chemistry*; D013237:Stereoisomerism
C504080:3,5-dimethylphenylcarbamate; D000596:Amino Acids; D004952:Esters; D048448:Phenylcarbamates; D011134:Polysaccharides; D002482:Cellulose; D000688:Amylose
Axial dissymmetry; Enantiomer separation; HPLC; Polysaccharide-based chiral stationary phase; Unusual amino acid