Simulated preparative enantiomeric separations

Advances in preparative enantioseparation by simulated moving bed (SMB) chromatography have occurred in the last 10 years. SMB was invented in the 1960s and was used by the petrochemical and sugar industries. Now with the improvements in stationary phases and hardware it is an option for the large-scale preparation of enantiomerically pure material. The majority of the latest published data are using either amylose- or cellulose-based phases because of their selectivity. There are now examples in the literature of the commercial separation on the multi-ton scale.8... 

Although gas chromatography (GC) is a well established method for the analytical determination of enantiomeric purity, the number of preparative applications is quite limited. Most of these preparative applications by gas chromatography have been recently reviewed [181] and were performed on a relatively small scale. The method is particularly suited for volatile compounds such as the inhalation anesthetic agents enflurane, isoflurane and desflurane [182] and it has also been recently applied to the resolution of racemic a-ionone [183]. The feasibility of separating the enantiomers by gas phase simulated moving bed chromatography has also been demonstrated for the first time and was applied to the anesthetic enflurane (Fig. 6.18) [184]. However, the productivity of the system was relatively low. 

The simulated-moving-bed technique (1,2) is a preparative technique for binary separations, specifically, the separation of two compounds or the separation of oiM compound from Ae rest of the world. In the second case, it is necessary that the peak of interest elutes either first or last in the chromatogram. The simulated moving bed is the chromatographic technology that uses the paddng and the solvent most efficiently. This fact, combined with the fact that it is a binary separation technique, makes it ideal for the prqiaration of chirally pure compounds from an enantiomeric mixture at industrial scales. 

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