High-yielding crystallisation of a single enantiomer from a racemic mixture by seeding induced deracemisation

15 August 2004

The propensity of a proportion of homochiral molecules to crystallise as conglomerates is the basis of the method of enantiomeric resolution of racemates by entrainment (see Topical Tip, Feb 27, 2004). If this is combined with epimerisation, it is possible to convert all of a racemic mixture into a crystalline single enantiomer.

A truly spectacular illustration of this was presented at a recent Scientific Update conference. Shinkai and coworkers* showed that by careful selection of solvent and base, plus seeding with crystals of the desired single enantiomer, an 80% yield of high purity single enantiomer was obtained directly from racemic input material. This was claimed to be reliably scalable.

* I. Shinkai (Beta-Chem), presentation at 9th International Conference on Organic Process Research and Development, Osaka, Japan, April 2004, organised by Scientific Update.