Prediction of the efficiency of diastereoisomer separation on the basis of the behaviour of enantiomeric mixtures

The composition of a crystalline diastereoisomer (eeDIA) is determined either by the eutectic composition of the racemic compound (eeEuRac) or that of resolving agent (eeEuRes) and the higher ee value has the more dominant effect.</p

The pH-dependency of diastereomeric salt resolutions with amphoteric resolving agents

We have analysed the role of pH in the diastereomeric resolution of racemic mandelic acid with (S)-phenylalanine and (R)-3-(aminomethyl)-5-methylhexanoic acid [(R)-Pregabalin] enantiomers. The adjusted pH had an effect on the optical purity and yield of the mandelic acid enantiomeric mixtures isolated from the diastereomeric salts. We showed that the pKa of the carboxyl group of the amphoteric resolving agents should be considered during the pH optimisation of diastereomeric salt resolutions. </jats:p

Regularities between Separations of Enantiomeric and Diastereoisomeric Mixtures. Prediction of the Efficiency of Diastereomeric/ Enantiomeric Separations on the Basis of Behaviour of Enantiomeric Mixtures

The driving force of the formation of the homo- and heterochiral associates in the mixtures of chiral compounds is, probably, the effort of the system to separate the most symmetric associates from the less symmetric ones. A possible way to achieve separation of these associates is the distribution between two phases. Therefore, during the separation of (a certain part) diastereoisomers similar trends can be observed as in course of the distribution of enantiomeric mixtures between two phases, although in the first case a third chiral compound (namely the resolving agent) is present. Of course in this case the formation of symmetrical associate is not so obvious as in case of enantiomeric mixtures. It should be noted that thus the outcome may be modified by the intervention of kinetic control. It can be concluded that the structure of chiral compounds encodes the result of the (optical) resolution