U.S. Department of Agriculture, Science and Education Administration, Western Regional Research Center, Berkeley, CA 94710, U.S.A.
Abstract:
Two new labdane diterpene acids have been isolated from Grindelia humilis. The spectroscopic properties of the acids and their derivatives, as well as conversion to methyl 6-oxogrindelate, showed that they were the epimeric pair 6α-hydroxy- and 6β- hydroxygrindelic acid. A series of 11 diterpene acids were surveyed for their feeding deterrency towards the aphid Schizaphis graminum. The substances tested showed a wide range of activity.