Reaction of Methyl 4,5-Epoxy-(2E)-pentenoate with Arenes. II. Application to the Synthesis of (±)-Curcudiol, (±)-Curcuphenol, (±)-Curcuhydroquinone, and (±)-Curcuquinone

Four bisabolane sesquiterpenes, (+)-curcudiol (2), (±)-curcuphenol (3), (±)-curcuhydroquinone (5) and (±)-curcuquinone (6), were synthesized based on the reaction of methyl 4,5-epoxy-(2E)-pentenoate (1) with methoxytoluenes in the presence of boron trifluoride etherate.