An unusual triterpene fatty acid conjugate from Dodonaea caespitosa

An unusual triterpene fatty acid conjugate was isolated from the leaf resin of Dodonaea caespitosa. Its structure was formulated through spectroscopic analysis of the acetylated natural product and its hydrolysis products (p-hydroxydihydrocinnamic acid, (S)-(+)-8,16-dihydroxypalmitic acid and 30-hydroxybetulin). The stereochemistry of the hydroxyl at C8 of (S)-(+)-8,16-dihydroxypalmitic acid was determined by conversion to the known (S)-(+)-(8)-hydroxypalmitic acid using a Barton–McCombie deoxygenation reaction.