Thalidomide Drug - [Enantiomers]

Welcome,

Before we start any discusions about the thalidomide drug we need to know few basic facts. To fully understand how thalidomide works it is necessary to familiarise with the term ‘enantiomer’.

“Enantiomers are optical isomers which are nonsuperimposable mirror-image structures.” (Prof Derek Cheung, 2007)

In other words these molecules are like a mirror reflections. They may look identical but they cannot be fully covered and laid on top of each other. That property of nonsuperimposability is called chirality. They have a chiral centre carbon. By the term ‘chiral’ it means that a carbon atom has 4 different, therefore nonidentical atoms or groups attached to it. That tetrahedral arrangement results in the existence of two enantiomers, which can be easily distinguished because they have the ability to rotate the radiation of plane-polarized light. A dextrorotatory (+)enantiomer has the clockwise direction whereas a levorotatory (-)enantiomer has the counterclockwise direction.

Image 1. shows two enantiomers: left is (-) enantiomer, right is (+) enantiomer.

A mixture of equal (50/50) amount of the (+) and (-) enantiomers is called a racemic mixture.

Until next time,
yours MPN

Reference
Prof Derek Cheung (2007) Thalidomide: A Controversial Chiral Drug. Quality Education Fund, Hong Kong
Boonrawd Wongsawat (2008) Stereoisomerism – Optical Isomerism http//www.promma.ac.th/main/chemistry/boonrawd_site/isomer_files/alanineisom.GIF last visited 20.11.2011