926 (2001) 229–238 Journal of Chromatography A, www.elsevier.com / locate / chroma High-performance liquid chromatographic enantioseparation of b-amino acids a, b b c * ´ ´´ ¨¨ A. Peter , L. Lazar , F. Fulop , D.W. Armstrong a ´ ´ Department of Inorganic and Analytical Chemistry, University of Szeged, Dom ter 7, H-6720 Szeged, Hungary b ¨ ¨ Institute of Pharmaceutical Chemistry, University of Szeged, Eotvos utca 6, H-6720 Szeged, Hungary c Department of Chemistry, Iowa State University, Gilman Hall, Ames, IA, USA Received 11 April 2001; received in revised form 19 June 2001; accepted 28 June 2001 Abstract Direct and indirect high-performance liquid chromatographic methods were developed for the enantioseparation of b-amino acids (b-substituted-b-alanines). Direct separation involved the application of chiral columns: Crownpak CR(1), Chirobiotic T and Chirobiotic R. Indirect separation was based on precolumn derivatization with 2,3,4,6-tetra-O-acetyl-b-D- glucopyranosyl isothiocyanate or N-a-(2,4-dinitro-5-fluorophenyl)-L-alanineamide (Marfey’s reagent), with subsequent separation on an achiral column. The chromatographic conditions were varied to achieve optimum separation.  2001 Elsevier Science B.V. All rights reserved. Keywords: Enantiomer separation; b-Amino acids 1. Introduction methods to control the enantiopurity of the final products. b-Amino acids have increased in importance in For these purposes, chromatographic separations the past decade [1,2]. They are important con- are widely used. Successful high-performance liquid stituents of many natural products, and their free chromatographic (HPLC) methods for the enantio- forms and derivatives exhibit interesting pharmaco- resolutions include indirect and direct methods. The logical effects [3–10]. b-Amino acids can be used as indirect methods involve precolumn derivatization building blocks for the preparation of modified with chiral derivatizing agents (CDAs), with sub- (unnatural) analogues of biologically active peptides. sequent separation of the diastereoisomers on an Oligomers of b-amino acids ( b-peptides) fold into achiral column [18,19]. Direct methods are per- compact helices in solution [11–16]. In consequence formed by ligand-exchange chromatography (LEC) of the wide-ranging utility of these compounds, [20,21], or by the application of chiral stationary much attention has been paid to their enantioselec- phases (CSPs) [22,23]. tive synthesis [1,2,8,17], which requires analytical The HPLC enantioseparation of b-amino acids started in the 1970s. Winnacker et al. [24] separated dipeptide diastereomers containing b-amino acids. *Corresponding author. Tel.: 136-62-544-000; fax: 136-62- Davankov et al. [25] reported a preparative LEC 420-505. ´ E-mail address: apeter@chem.u-szeged.hu (A. Peter). method, while Lindner and Hirshbock [26] found 0021-9673 / 01 / $ – see front matter  2001 Elsevier Science B.V. All rights reserved. PII: S0021-9673(01)01078-0