LIQUID-CHROMATOGRAPHIC RESOLUTION OF RACEMIC AMINO-ACIDS AND THEIR DERIVATIVES ON A NEW CHIRAL STATIONARY-PHASE BASED ON CROWN-ETHER

A new high-performance liquid chromatography chiral stationary phase ( CSP) was prepared by bonding (+)-(18-crown-6)-2,3,11,12-tetracarboxyli c acid to silica gel. The new CSP was employed in separating the two e nantiomers of various natural and unnatural racemic alpha-amino acids and their derivatives. All natural acid unnatural racemic alpha-amino acids tested were resolved with reasonable separation factors on the n ew CSP, except for proline, which does not contain a primary amino gro up. Racemic alpha-amino acid derivatives were also tested for their se parability on the new CSP. In general, N-monoalkyl amides of alpha-ami no acids were resolved better than the corresponding free alpha-amino acids. However, N,N-dialkyl amides and esters of alpha-amino acids wer e not resolved as well as the corresponding free alpha-amino acids, ex cept for phenylglycine derivatives. In the case of phenylglycine, both N-monoalkyl and N,N-dialkyl amides of phenylglycine were resolved bet ter than phenylglycine itself and its ester derivative. (C) 1998 Elsev ier Science B.V. All rights reserved.