Resolution by Formation and Fractional Crystallization of Diastereomeric Salts

In solution, both strong and weak interactions can develop between the resolving agent and the enantiomers to be separated (Fig. 3.1). With resolution via diastereomeric salts, preferential precipitation of that particular salt can, in principle, be anticipated in which the total of secondary interactions is higher. In some cases, however, interactions between the enantiomers themselves are stronger than those present in the salts, whereupon it is the racemic phase that crystallizes.