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 -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 -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 -position of N-protected -amino acid derivatives locating toward to the inside of grooves.