Chirality and its implications for the pharmaceutical industry

After a short introduction to the general phenomenon of chirality, the implications for synthesis and application of chiral drugs are discussed. In a first part, the historical development is briefly described. Up to the 1950s, most medications were either of natural origin, or made semi-synthetically from natural products. In these cases, only one enantiomer was usually present, i.e., the drugs were used as single enantiomers. This changed when totally synthetic drugs began to dominate the market, since these drugs were usually prepared, tested and applied as racemates. Due to the observation of negative effects such as the Thalidomide (Contergan) tragedy, stricter regulations were introduced and as a consequence, chiral drugs are now almost exclusively applied as single enantiomers. In a second part, the challenges for the industrial synthesis of chiral drugs are discussed. The various approaches to prepare enantiomerically pure compounds are briefly described and discussed in the context of industrial process development. Important for the choice of the production technology are criteria such as time constraint, complexity of the molecule, cost considerations and maturity of the technology.