Flexible Molecules with Defined Shape—Conformational Design

Chemists have for a long time considered molecules simply in terms of their constitution. The importance of molecular shape was recognized perhaps for the first time by the semio‐chemists, who were interested in the interactions of fragrant substances with a receptor. Apart from the case of rigid molecules, our ideas and concepts of molecular shape simply reflect an instantaneous situation, because flexible molecules take advantage of the whole range of conformation that is available to them. Nature frequently utilizes flexible molecules whose conformational space is restricted, in other words, molecules that can adopt only a few preferred conformations. This review discusses some of the principles that nature employs in order to impart a defined shape to flexible molecules. The purposeful application of these principles then allows the conformational design of molecular skeletons. For corrigendum see DOI: 10.1002/anie.199215401 For corrigendum see DOI: 10.1002/anie.199216571