ENANTIOMERIC RESOLUTION OF AMINO-ACID DERIVATIVES BY HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY ON CHIRAL STATIONARY PHASES DERIVED FROM L-PROLINE

The enantiomeric separation of a series of N-3,5-dinitrobenzoyl amino acid esters was investigated by normal-phase high-performance liquid chromatography on four chiral stationary phases (CSPs) derived from L-proline as chiral selector. The chiral selector was covalently bonded to silica gel by the use of either a spacer with a three (CSP1 and 2) or eleven (CSP3 and 4) carbon chain length. The protective groups were benzyloxycarbonyl or tert.-butoxycarbonyl. The natures of the protective group and the spacer were important for chiral recognition. A spacer with eleven carbons allows a better resolution of a large number of N-3,5-dinitrobenzoyl amino acid esters. The mobile phase can induce major changes in the behaviour of solutes, thus leading to better enantioselectivity.