Calculation of the efficiency of optical resolutions on the basis of the binary phase diagram for the diastereoisomeric salts

Abstract

In resolutions based on the solubility difference between pairs of diastereoisomeric salts, the maximum efficiency (parameter S) can be calculated from a knowledge of the eutecic composition of the binary T–x diagram. We demonstrate that an approximate binary phase diagram can be determined from the DSC melting curve of a single diastereoisomeric salt mixture, namely the global 1:1 mixture of diastereoisomeric salts isolated from a resolution without separation. Data estimated with the reported method are compared to the experimental results of seven resolutions. The method has proved to be efficient for diastereoisomeric salt systems forming crystalline conglomerates. Comparison of calculated S values obtained from a single racemic substrate with different resolving agents facilitates selection of the best resolving agent in the set.