Chiral separation and modeling of the three-chiral-center β-blocker drug nadolol by simulated moving bed chromatography

Nadolol, a β-blocker used in the management of hypertension and angina pectoris, has three chiral centers and is currently marketed as an equal mixture of its four stereoisomers. Resolution of three of the four stereoisomers of nadolol was obtained previously by HPLC, with a complete separation of the most active enantiomer (RSR)-nadolol, on a column packed with perphenyl carbamoylated β-cyclodextrin (β-CD) immobilized onto silica gel. In this study, continuous separation of the target enantiomer of (RSR)-nadolol from its racemic mixture (which is a ternary mixture in the chromatographic system) was studied by non-linear SMB chromatography. Different regions of (2, 3) and (1, 2) complete separation regime were determined in the (m2, m3) region and the effect of non-linearity such as overall feed concentration and component composition on the separation performances was investigated. A direct simulation approach has been proposed to simulate the SMB separation performance for the pseudo-binary mixture of nadolol. The simulation was conducted on the basis of a shortcut method constituted only of the weak-key and strong-key components. The performance of the cyclic steady-state behavior of the SMB unit was predicted reasonably well. It was also discussed quantitatively that the complete separation region obtained from the shortcut method is a subset of the true complete separation region and the optimal separation conditions obtained differed slightly from the “true” separation.