ENANTIOMER SEPARATION OF N-t-BOC AND N-CBZ α-AMINO ACIDS AND THEIR ESTERS ON POLYSACCHARIDE DERIVED CHIRAL STATIONARY PHASES

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.

Keywords:

• α-Amino Acid
• chiral recognition
• enantioseparation
• HPLC
• polysaccharide derived chiral stationary phase

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.

E_es is the energy of electrostatic interaction including hydrogen bond and coulombic interaction.

E_vdw 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): E_es + E_vdw.