Isomerization-Crystallization Method in Optical Resolution

Abstract

In recent years, synthetic method by the combination of isomerization and crystallization is studied intensively, especially in the practical optical resolution. In this paper, this isomerization-crystallization method is introduced from a point of view of practical organic synthesis. A number of examples of this isomerization-crystallization method in optical resolution, many of which were often reported as the example of second-order asymmetric transformation phenomena, are classified into following two groups, and reviewed.
(1) Epimerization-crystallization method.
(2) Racemization-preferential crystallization method.
The potentialities and difficulities of each method are also discussed. The compounds resolved by this methods are α-amino acid derivatives, cyanohydrin derivatives, α-aromatic carboxylic acid esters, and so on.