Micropreparative enantioseparation

GC is basically a technique for analytical enantioseparations. However, micropreparative separations are also feasible using this technique. The most impressive example of the application of chiral GC for micropreparative enantioseparation of drug enantiomers is the chiral inhalation anesthetic drug, enflurane. According to recent data, the enantiomers of isoflurane may have different pharmacological properties [94]. For the isomeric compound enflurane (Fig. 3) a more intensive metabolism was established for the (ft)-(-)-enantiomer compared with the (S)-(+)-enantiomer [95]. Enflurane is a gas and therefore, the most favorable method for the enantioseparation will certainly be GC. Analytical-scale enantioseparations of this compound have been reported using various CD derivatives as CSPs [97]. The micro-... 

Ivory s group published very interesting examples of micropreparative enantioseparations based on the FCCE principle very similar to that described in [15]. This group also developed an electrophoretic separation system shown in Fig. 6 [91, 92, 94] as an analogue of the simulated moving bed (SMB) system well known in chromatography [95]. 

Based on the general synthetic scope of this book, the subject of enantioseparations is treated in this chapter mainly from the viewpoint of micropreparative- and preparative-scale production of enantiomerically pure compounds. Analytical aspects are treated to a very limited extent and a quantification of enantiomers in biological fluids as well as stereoselec-... 

In summary, capillary electromigration techniques possess real potential to compete successfully with chromatographic methods for analytical enantioseparations. However, the future will show if these techniques may be also used for obtaining pure enantiomers on a micropreparative scale. 

As shown in [15] this concept may allow for the design of a separation system in such a way that two enantiomers certainly possessing the electric charge of the same sign will migrate toward opposite electrodes, which means that the enantioseparation factor becomes infinitely large (Fig. 2) [15], This technique certainly may be applied for micropreparative purposes also as well as for separations of achiral analytes not only in a binary mixture but also in multicomponent mixtures. 

Chiral CE is considered basically to be a technique suitable for analytical-scale enantioseparations. However, this technique possesses a certain potential for micropreparative-scale enantioseparations [15, 85-93],... 

In all works devoted to micropreparative-scale enantioseparations using electrophoretic techniques, there are still many practical problems to be solved before these techniques become a viable alternative to other methods for obtaining enantiomerically pure compounds. 

---