Example of a Diastereomeric System

The example to be represented refers to a binary system of two epimers a and ) of a diastereomeric pharmaceutical intermediate. The epimers are obtained as an 1 1 mixture from chemical synthesis and have to be separated. The chemical formula is not of significance for discussion of the results. 

Both epimers form solid solutions with the respective other one, with limits of miscibility of 5% (Una and 3% a in These boundaries will limit the depletion of the unwanted component by crystallization. 

purity demands of 99% as often required for fine chemicals cannot be fulfilled here in one crystallization step. As will be described in Chapter 7, fractional crystallization is capable to further (stepwise) deplete the unwanted component in the product to the expense of yield. 

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