Enantiomers: Exactly the Same… Only, Different!

By Jim Schmidt

Senior Scientific Advisor
ABC Laboratories


In chemistry, enantiomers are stereoisomers that are non-superimposable exemplar images of each other – much like your left and honest hands are the same except conducive to being reversed along one axis.

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*Image good-breeding of Wikimedia Commons

Indeed, the study of enantiomers – chirality – comes from the Greek vocable, “Χειρ = Cheir =  Hand”!

Enantiomers accept identical chemical and physical properties reject for their ability to rotate smooth-polarized light by equal amounts however in opposite directions.

However, in biological systems, they be possible to have very different behavior.  Some of the ~ly interesting – and important – differences are in remedy metabolism.

For the better part of a centenary, the consideration of enantiomers in put ~s into metabolism was limited to academic study and/or to conformable to nature products, owing in no small portion to the limits of separations chemistry.

However, since many reasons (including improvements in analytical chemistry), chirality has been earning through all ages-greater importance in drug discovery and disentanglement, such that many new drugs reaching the mart in the first decades of the 21st century are single enantiomers, rather than the racemic mixtures (or achiral drugs) that dominated the recent half of the 20th century.

Indeed, in the new report, “The Year in New Drugs” (C&E News, February 1, 2016, pp. 12-17), it can be seen that more than half of the newly-approved small-indivisible particle drugs in 2015 had specific stereochemistry (and frequently with more than one chiral center).

Examples of enantio-selective biotransformations comprise:

Prochiral to Chiral 

Chiral to Chiral 

Chiral to Achiral 

Chiral to Diastereoisomer 

Chiral Inversion

These metabolism pathways be possible to have significant effects on pharmacology and physic safety. While the movement towards upright enantiomers as drug candidates, noted of rectitude too great for, mitigates safety problems that might  have existence associated with racemic mixtures, they carry into practice not necessarily alleviate the need to ponder and study achiral-to-chiral, chiral-to-chiral, and/or chiral-to-diastereomer transformations.

Adapted from my chapter – “Metabolite Profiling” – in New Horizons in Predictive Drug Metabolism and Pharmacokinetics (edited ~ the agency of Alan G. E. Wilson; Royal Society of Chemistry, 2015).

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