Isolation of high-purity friedelin and 3-hydroxyfriedel-3-en-2-one from cork smoker wash solids

Abstract Cork smoker wash solids (black wax) that is obtained in the process of making corkboard by treating the ground cork with superheated steam is useless waste, generating environmental problems. On the other hand, black wax is a rich source of friedelin (1) and 3-hydroxyfriedel-3-en-2-one (3), pentacyclic triterpenoids belonging to the friedelane family. In the present work, a simple, fast, and efficient procedure for the extraction of highly purified friedelin and 3-hydroxyfriedel-3-en-2-one from black wax is presented. Extraction of black wax with hexane or acetone afforded a mixture of friedelin and 3-hydroxyfriedel-3-en-2-one. However, chromatographic separation of 1 and 3, due to their very similar Rf coefficients, is difficult, especially on a multigram scale. Therefore, the conversion of 3-hydroxyfriedel-3-en-2-one to an acetyl derivative 4 was proposed by acetylation of the above mixture. Appropriate selection of the eluent sequence allows for rapid and efficient separation of the resulting mixture of 1 and 4.