21 February 2015 - Catalysis

Zhang Tiefenbacher 2015.PNGIn an example of lab imitating nature tail-to-head terpene cyclization is found to take inside the cavity of a certain resorcinarene mimicking an enzyme (Zhang & Tiefenbacher DOI). The resorcinarene capsule is hydrophobic with a cavity of 1.4 A. The walls are aromatic allowing favourable cation-pi interactions. The cavity also act as a brønsted acid. When the terpene geraniol and capsule (10%) were combined in chloroform the main product was first linalool and finally in the course of hours eucalyptol. Six solvent molecules can fill the capsule. one substrate molecule replaces three solvent molecules. Adding tetrabutyl ammoniumbromde blocks the cavities and no cyclisation takes place. Nerol was also converted to eucalyptol. Likewise geranyl acetate was found to cyclisize to terpinene.