The separation of enantiomers by means of liquid chromatography (LC) using chiral stationary phases is based on the reversible diasteromeric association between the chiral environment in the column and the enantiomers in the solution (S. Allenmark, xe2x80x9cChromatographic Enantioseparationxe2x80x9d, 2nd Edition, Ellis Horwood, N.Y., 1991, pp. 1007-1008).
The chiral stationary phases for LC are normally classified on the basis of their general structures. One group is based on either synthetic or natural polymers and is totally or intrinsically chiral.
Another group is made up of chiral selectors with a low molecular weight bound to a solid, incompressible, matrix, generally silica. The latter provides remarkable advantages with respect to the former since the chiral selectors can be designed rationally (K. B. Lipkowitz, Modelling Enantiodifferentiation in Chiral Chromatography, in xe2x80x9cA Practical Approach to Chiral Separation by Liquid Chromatographyxe2x80x9d, G. Subramanian Editor, VCH, Weinheim, 1994, pp. 19-55).
This implies that they can be selected on a rational basis; in fact, their enantioselective features can often be evaluated by means of NMR studies or can be singled out thanks to computer modelling according to the various types of chemical interactions.
Among the most frequently used chiral selectors bound to a solid support it is worth quoting the xe2x80x9ccrown ethersxe2x80x9d (E. P. Kyba et al., J. Am. Chem. Soc., 1978, 100: 4555-4568), the charge-transfer complexes (W. H. Pirkle et al., J. Am. Chem. Soc. 1986, 108: 352) the chiral selectors based on hydrogen bonds (see e.g. S. Hara et al., J. Chromatogr., 1979, 186: 543) and other types of chiral selectors (P. Salvadori et al., Tetrahedron, 1987, 43, 4969).
All these products exhibit some limitations with respect to their enantioseparating ability, which are due either to the high number of functional groups or structural subunits that participate in the interaction with the enantiomers in solution.
The range of application of chiral selectors should therefore be widened up so as to promote the use and versatility of chromatography based on stationary chiral phases.
Is a fungicide widely used in agriculture; some of its derivatives such as glutathione are described in Tetrahedron, 1995, 51: 2331. None of these derivatives is used in chromatography.
This invention relates to new derivatives of 1,3-dicyano-2,4,5,6,-tetrachlorobenzene containing one or more chiral groups and one group acting as a spacer. The stationary phases obtained from these derivatives provide an efficient separation of enantiomers.
The present invention describes new chiral stationary phases, and the optically active compounds therein contained. The optically active compounds contained in the stationary phases are represented by the formula of structure (I), which comprise at least one asymmetric carbon atom and a substituent acting as a spacer. The stationary phases of the present invention can be used in the preparation of chromatographic columns useful for the analytical and preparative separation of enantiomers.