Revision of the Phytochemistry of Eremophila sturtii and E. mitchellii.

Eremophila sturtii and E. mitchellii are found in the arid and temperate regions of Australia and, because of their similar appearances, are often confused. Previous phytochemical investigations have described mitchellene sesquiterpenes (1-5) reported from E. mitchellii but are here demonstrated to be from E. sturtii. A previous study that described serrulatic acids (16 and 17) from a species reported as E. sturtii actually used E. mitchellii. In addition, two new C-15 modified analogues, mitchellenes F (14) and G (15), were isolated from E. sturtii. The absolute configuration of 14 was determined with the first X-ray structure of a compound with the mitchellene skeleton.