Mirror, mirror on the wall ... stereochemistry in therapeutics.

Stereoisomers are molecules that have the same structural formulas but differ in the orientation of their individual atoms in space.1-3A special form of isomerism occurs when an individual atom, or chiral center (usually a carbon), has four different substituents arranged in a tetrahedral fashion. In this case, two mirrorimage orientations, called enantiomers, of these substituents around the chiral center are possible. Enantiomers are identified by the way in which they rotate polarized light: the terms dextrorotary (dor [+]-enantiomer) and levorotary (1or [-1-enantiomer) are used, as is an alternate (and not interchangeable) system in which enantiomers are more rigorously termedRand S-.'A number of