ABSTRACT
In the course of their development starting more than one billion years ago, living organisms opted at some point for one enantiomer of the chiral compounds they are built up. Thus, all protein-forming amino acids have an
configuration, nucleic acids exclusively contain
sugars, etc. Consequently, living systems respond stereoselectively to any chiral substance introduced; that is, different enantiomers of a compound (e.g., a drug) often have different biological effects. In addition to the main and intended effect of a drug, it has several side effects which are, to a first approximation, randomly distributed among the antipodes of the compound. Therefore, if it is found that the desired effect of a chiral drug is associated with one of its enantiomer, it is rational to apply only the active enantiomer, thereby reducing the side effects to about half per unit weight. Also, with chiral insecticides such as the pyrethroids, enantiomerically pure agents are generally much more effective and less burdensome to the environment. It is thus no wonder that today registration of a chiral drug in its racemic form is extremely difficult and pharmaceutical companies invest considerable effort to be able to market enantiomerically pure products.
