Chiral Resolution

Chiral resolution, also known as enantiomeric resolution, is a stereochemical technique that separates racemic substances into their enantiomers. It is a critical tool in the manufacture of optically active molecules, including medicines. Optical resolution is another phrase for the same thing. The downside of using chiral resolution to generate enantiomerically pure molecules is that at least half of the beginning racemic mixture must be discarded. One method of eliminating this waste is asymmetric synthesis of one of the enantiomers. The most typical approach for chiral resolution includes reacting the racemic mixture with chiral derivatizing agents, also known as chiral resolving agents, to produce a pair of diastereomeric derivatives. The derivatives are then separated by ordinary crystallisation and converted back to the enantiomers by removing the resolving agent. The method is time-consuming and is dependent on the diastereomers' differential solubilities, which are difficult to anticipate. Often, the less soluble diastereomer is sought, while the other is discarded or racemized for reuse. It is typical to test many resolving agents. A typical derivatization includes the production of a salt between an amine and a carboxylic acid. Simple deprotonation then provides the pure enantiomer. Tartaric acid and the amine brucine are two examples of chiral derivatizing agents. Louis Pasteur reintroduced the method (again) in 1853 by resolving racemic tartaric acid with optically active (+)-cinchotoxine.