Some of nature's most fascinating phenomena are due to a very simple fact: you cannot superimpose
the mirror image of a nonsymmetrical object onto the object itself. This property is called chirality.
Nearly all important biological molecules are
chiral. In fact, the chemistry of life is built almost exclusively on left-handed amino acids and
right-handed sugars, a pattern known as the 'homochirality of life'.
Pharmaceuticals are often chiral since in many cases only drugs with the correct handedness
are capable of executing a proper 'hand shake' at the receptor site. Today, about 50 of the top
100 drugs are marketed as single enantiomers, and 80 percent of drugs now entering the drug development
process are single enantiomers.