Bisabolane Sesquiterpenes: Synthesis of (R)-(+)-Sydowic Acid and (R)-(+)-Curcumene Ether.

A stereoselective synthesis of(R)-(+)-sydowic acid 1 and (R)-(+)-curcumene ether 2 is described. The enantiomerically pure tetrahydropyran building block (R)-(-)-cinenic acid 5 is obtained by resolution of the racemic acid. The aromatic moiety is constructed using a benzoannulation reaction as a key step. An easy way to the title compounds in racemic form is also reported.