4. Geometric isomerism and drugs

Given that differences in drug activity are related to the spatial structure of the asymmetric target on which they act, it's worth mentioning the importance of geometric isomerism. This results from the presence of substituents around a double bond, leading to Z/E or cis/trans isomerism. Geometric isomers such as cis and trans butenes or malic and fumaric acids have no optical activity. They are characterized by the absence of rotational freedom around the bond (figure 31 ).

This isomerism also occurs in the presence of a double bond between a carbon atom and a heteroatom (e.g. nitrogen) and in alicyclic derivatives with two chiral centers (dimethylcyclohexanes) (figure 32...