Page 232 - Chiral Separation Techniques

210 8 Nonchromatographic Solid-Phase Purification of Enantiomers

compares favorably to current industry practice on these factors, including: (i)
reduced number of process steps; (ii) high chemical, optical and volume yields; (iii)
high-feed throughput; (iv) more open-ended solvent choice; (v) minimized solvent
usage; and (vi) low resin consumption.

8.4.1 Reduced Number of Process Steps

Because the ChiraLig™ resin displays both high chemo- and enantioselectivity, the
separations method allows for simultaneous chiral resolution and chemical separa-
tion, thus reducing the number of steps necessary to achieve high purity goals. The
higher α-values of the ChiraLig™ resin make it possible to reach desired purities in
fewer separations stages.

8.4.2 High Chemical, Optical and Volume Yields

High yields are possible due to the large capacity of the ChiraLig™ for the single
enantiomer on each load cycle. A significant percentage of the available binding
sites are used in each cycle to bind the eutomer.

8.4.3 High-Feed Throughput

The high selectivity of the system results in high-yield throughputs, and close to
100 % time usage of the system for feed introduction.

8.4.4 Open-Ended Solvent Choice

The ChiraLig™ resins are rugged and resistant to solvent erosion. The organic li-
gands are covalently bound to silica, polystyrene, or polyacrylate supports. This
covalent linkage provides for long life and multiple recycle. Solvent choice is often
open-ended, and the user is able to choose the best solvent in order to maximize
other considerations, including achieving maximum solubility. There is the require-
ment, however, of either pH or solvent change to perform the stripping or elution
step for each stage.

8.4.5 Minimized Solvent Usage

Solvent usage is drastically reduced due to several factors. The feed can be flowed
through the ChiraLig™ columns nearly continuously and high feed concentrations
can be used as needed. Rapid loading occurs due to reasonable binding kinetics. The
subsequent release (elution) step is accomplished in just a few bed volumes, with