Chiral chromatographic methods problems

Other methods for racemate separation include fractional crystallization of diaster-eomers with optically pure counter ions [304], conglomerate crystallization [305], and various chromatographic techniques incorporating both mobile and stationary chiral phases [306]. All of these techniques involve intermolecular interactions of some kind. While it is theoretically possible to model these, by using molecular mechanics, the complexity of the problems involved have so far been prohibitive when the time required for a thorough design is compared with experimental trial-and-error studies. 

At first we tried to address the problem with Moreau s method of kinetic resolution which has been applied with great success to compounds of central chirality (ref. 18). To our knowledge this technique has not yet been used for compounds with axial chirality. To be on safe ground, we had to calibrate the effects first with compounds of similar structure and known absolute configuration. We selected 2,2 -dihydroxy-1,1 -binaphthyl (31) as an example and reacted it in the usual way with an excess of racemic 2-phenyl butanoic anhydride in the presence of pyridine. The optical excess in the remaining anhydride was determined by means of the gas chromatographic variant of Brooks and Gilbert (ref. 19) (Scheme 6). 

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