Higher isoprenoids—VIII: Diterpenoids from the oleoresin of hardwickia pinnata part 1: hardwickiic acid

The oleoresin from Hardwickia pinnata Roxb. is shown to be a complex blend of sesquiterpenes and diterpenes. (?)-Copaene, (?)-caryophyllene and humulene account for over 90% of the sesquiterpenes present. The diterpenes, which constitute some 60% of the oleoresin, have been found to consist of a series of closely related new diterpenoids of ent-clerodane type. Evidence leading to the elucidation of the absolute stereostructure of the main diterpenoid-hardwickiic acid—is presented.