Abstract
Liquid chromatographic enantiomer separation of N-t-BOC and N-CBZ α-amino acid, methyl ester, and ethyl ester derivatives was performed on chiral stationary phases (CSPs) based on polysaccharide derivatives. Good resolution of N-t-BOC and N-CBZ α-amino acid derivatives was achieved on Chiralcel OD, Chiralcel OF, and Chiralpak AD, respectively. Enantioselectivites of N-CBZ protected derivatives were found better than those of N-t-BOC protected derivatives. Moreover, the results of liquid chromatography and computational chemistry suggest that L-form is more retained in the case of carboxylic group of enantiomer locating toward to the inside of grooves, on the other hand, D-form is more retained in the case of alkyl group of α-position of N-protected α-amino acid derivatives locating toward to the inside of grooves.
ACKNOWLEDGMENT
Byoung-Hyoun Kim and Sang Uck Lee contributed equally to this work.
Notes
Separation conditions refer to EXPERIMENTAL.
a Retention factor.
b Separation factor.
c Resolution factor.
d Absolute configuration.
Separation conditions refer to EXPERIMENTAL.
a Retention factor.
b Separation factor.
c Resolution factor.
d Absolute configuration.
e Not eluted D-form.
Ees is the energy of electrostatic interaction including hydrogen bond and coulombic interaction.
Evdw is the energy of van der Waals interaction.
a A: binding CSP wth enantiomer.
b B: CSP only.
c C: enantiomer only.
d Total E (total interaction energy): Ees + Evdw.