Chiral cognisance: a road to safer and more effective medicinal products.

A quarter of all synthetic medicinal drugs contain a mixture of equal proportions of two molecules that have the same chemical constitution but differ in the spatial arrangement of their constituent atoms such that each is a mirror-image of the other, like the right and left hand. Biologically, receptors which are stereospecific react with only one of the two components of the mixture to produce the desired therapeutic effect, while the other is inactive or may interact with different receptors to cause undesirable, even toxic, effects. Development of syntheses that produce a preponderance of the required form, and efficient separation of mixtures, will result in safer and more effective medicinal products.