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Abstract
The propensity of helical homochiral polymers derived from amylose to resolve optical isomers is being exploited intensively for the production of active pharmaceutical ingredients (APIs), using either high performance lipid chromatography (HPLC) or the simulated moving bed (SMB) principle. Several lots of an amylose derived stationary phase, Chiralpak® AS™, and its successor, Chiralpak® AS-V™, were compared by pulse injections with increasing amounts of various racemates in order to determine the loading capacity and the competitive adsorption isotherms. Software simulations allowed to assess the possible effects due to the observed variations between the chiral stationary phases (CSPs) on the performance of a pilot SMB unit.
The obtained results were verified by two multi-kilogram separations performed under current Good Manufacturing Practice (cGMP) guidelines employing the two CSPs. The results of the two production runs are discussed in the light of the recently introduced “triangle theory,” which allows to account for the overload conditions prevailing under preparative chromatographic conditions and to predict optimal operating conditions.
Under optimized conditions the enantiomer separation of 1.4 kg racemate/kg stationary phase per day with purities >99.6% for the target enantiomer has been achieved.
Acknowledgments
The authors whish to thank Dr. W. Hauck, NOVASEP, Vandœuvre les Nancy, France for his efforts and support during the optimization of the separations, Dr. G. Cox, Chiral Technologies Europe, Strasbourg, France, for several interesting discussion on the properties of amylose derived CSPs and Prof. Dr. M. Mazzotti and Prof. Dr. M. Morbidelli, ETH Zürich, Switzerland, for many stimulating phone calls during the preparation of this manuscript.