Page 233 - Chiral Separation Techniques

8.5 Experimental Examples of Separations 211

rapid release of the pure enantiomer from the column. The resulting product con-
centrate is often of high tenor for easy collection and post-processing to the pure
enantiomer. Often the main limitation to the product concentrate tenor is the solu-
bility of the enantiomer in the elution solvent.

8.4.6 Low Resin Consumption

Resin consumption is low because of the highly efficient use of the capacity of the
resin for the enantiomer during each cycle, as well as the material stability of the
resin. The above benefits of the ChiraLig™ technology result in improved eco-
nomics for the large-scale separation.
The use of nonchromatographic technology overcomes some of the existing
issues one might have with the use of chromatography, including solvent consump-
tion, and low overall yields. Based on the work performed in IBC’s laboratories, and
our commercial experience in molecular recognition technology (MRT), the scale-
up of separations process systems based on ChiraLig™ is straightforward. Feasibil-
ity has been shown in the demonstration of the use of the principles described in this
chapter to achieve efficient separations. Implementation of production systems
involve the application of MRT scale-up principles already applied by IBC in the
chemical process industry where synthetic organic ligands attached to silica or poly-
meric supports are in use. Design principles used for these large-scale systems can
be applied to chiral applications, including column design, pre-filtration, flow meter-
ing and pumping, cycle control, construction materials, column aspect ratios, fill
volumes and number, and cycle timing.
In the next section, a few illustrative examples of the use of ChiraLig™ for the
analytical and three-stage preparative chiral separations involving amines and amino
acids are presented and discussed.

8.5 Experimental Examples of Separations

8.5.1 Analytical Separation of Amine Enantiomers

The analytical capability of these matrices has been demonstrated for chiral amines
[12, 13]. The procedure is illustrated in Fig. 8-4 for the separation of NapEtNH 4 +
–
ClO . Concentrated methanol/dichloromethane solutions of the racemic mixture
4
were placed on a column containing the chiral macrocycle host. The enantiomers of
the ammonium salts were resolved chromatographically with mixtures of methanol
and dichloromethane as the mobile phase. The amounts of R and S salts in each frac-
tion were determined by polarimetry. Because the chiral supported macrocycle inter-
acts more strongly with S salts, the R salt passes through the column first and the S
salt last, as seen in Fig. 8-4.