Synthesis of macrocyclic terpenoids by intramolecular cyclization V. transannular reactions of hedycaryol isomers

Thermal rearrangement and acid-catalyzed cyclization of all possible geometrical isomers of hedycaryol were investigated. From the stereochemistry of the products, the reacting conformations were deduced. While three (E,E-, E,Z- AND Z,E-) isomers reacted through the crossed conformations, Z,Z-isomer yielded products $\text{via}$ parallel conformations. The thermal reaction at higher temperatures revealed the additional pathways involving Cope rearrangement of elemols. All possible stereoisomers of elemol were synthesized. The structure of “epielemol” has to be revised.