3D Models of Thalidomide Stereoisomers

Most chiral substances used in medicine are prepared and marketed as racemic mixtures. This is because the reactions that produced the substances are usually not able to selectively make only one enantiomer, and to separate the mixture of enantiomers is often a very expensive process. Fortunately, in many cases both enantiomers have similar biological activities or the "wrong" enantiomer will simply be biologically inactive.

A terrible exception occurred in the case of the sedative thalidomide. Thalidomide was marketed in the 1960ís as a racemic mixture to pregnant women. It was being used to treat morning sickness. It was later discovered that one enantiomer acted as an antidepressant, and the other was both a mutagen and an anti-abortive. It led to serious birth defects in hundreds of babies. In this case, the "wrong" enantiomer appears to have been the cause of this tragedy.

The consequences of using a compound with the wrong stereochemistry can be very serious!