A Facile Cycloisomerization for the Formation of Medium and Large Rings via Allenes

摘要

The importance of macrocycles is readily apparent by the large number of biologically significant molecules that possess such a core, be it a carbocycle or heterocycle. Such ring systems may be thought to represent a compromise in the attempt to introduce conformational rigidity into acyclic structures in order to enhance biological potency. In small and normal-sized rings, the limits on flexibility mean that a ligand must be just right for the receptor, otherwise it will not fit properly. Medium andlarge rings have well-defined conformations also; however, a number of conformations frequently will lie close in energy to the global minimum. Thus, if the design is not perfect, the molecule may still be able to adapt itself to fit the receptor without an inordinate cost in energy.