Chiral high performance liquid chromatographic separation of enantiomers of alpha-methyl alpha-amino acids

The enantiomeric separation by chiral high performance liquid chromatograph y of derivatized and underivatized alpha-methyl alpha-amino acids was achie ved by two different methods. A cellulose tris(3,5-dimethylphenylcarbamate) chiral stationary phase column (Daicel Chiralcel OD) was used to resolve N -benzyloxycarbonylated methyl esters. Excellent separations of enantiomers were achieved with all the alpha-methyl alpha-amino acids examined. A colum n packed with octadecylsilanized silica coated with N,S-dioctyl-D-penicilla mine as a chiral ligand-exchange phase (Sumichiral OA-5000) was also used t o resolve the underivatized amino acids. Excellent to good separations of e nantiomers were achieved with a variety of underivatized alpha-methyl alpha -amino acids carrying aliphatic or aromatic side-chains by optimizing the a mount of the organic component and the concentration of the copper(II) ion in the hydro-organic eluent.