Since the tragic Contergan scandal it is well-known that one enantiomer may act as a very effective therapeutic drug, whereas the other enantiomer is very toxic. In order to avoid a reoccurrence of such a tragedy it is the responsibility of synthetic chemists to provide highly efficient and reliable methods for the synthesis of desired compounds in an enantiopure state.
Several methods are used to obtain enantiomerically pure material, which include classical optical resolution via diastereomers, kinetic resolution, use of enzymes and asymmetric synthesis.
Catalytic Asymmetric Synthesis has become a common tool for the synthesis of enantiopure compounds in industry and academia. The Nobel Prize in Chemistry 2001 has been awarded jointly to William S. Knowles and Ryoji Noyori “for their work on chirally catalysed hydrogenation reactions” and the other half to K. Barry Sharpless “for his work on chirally catalysed oxidation reactions”. Quite recently it was announced that Benjamin List and David MacMillan won the Nobel Prize in Chemistry 2021 for “the development of asymmetric organocatalysis”, clearly indicating the profound importance of asymmetric catalysis.
The relevance of asymmetric synthesis as a tool is widely acknowledged by organic chemists working in medicinal, pharmaceutical, agriculture and fine chemistry. Catalytic asymmetric synthesis has significant economic advantages over stoichiometric asymmetric reactions for industrial-scale production. Especially the use of Cinchona Alkaloids is the best example for applied Green Chemistry, using mild reaction conditions, environmentally friendly reaction procedures. Low toxicity of catalysts, easy recovery and reuse are important Green Chemistry requirements fulfilled by Cinchona Alkaloids.