3. Stereoisomerism and drugs

From a conceptual point of view, we had to wait until the beginning of the 20th century to note with Ehrlich the importance of the relationship between the structure of a substance and its activity, with the introduction of the notion of chemical receptor when studying the anti-parasite activity of dyes . A substance can only act if it can attach itself to its target, like a key and its lock (attachment of the dye to the parasite). Subsequently, the importance of the relationship between optical isomerism and biological activity progressed considerably, with Esson and Stedman's 1933 theory proposing a model involving three points of contact between a chiral molecule and its receptor (see