Terpenoids. XLII. A Convenient Stereoselective Transformation of 16-Exocyclic Methylene Group into Carboxy Group in ent-Kaurene and Its 19-Oic Acid

Abstract

By the two successive oxidative rearrangements using thallium trinitrate, ent-16-kaurene (1) was stereoselectively converted into ent-16α-kauran-17-oic acid (30). Further application of these reactions led to a convenient transformation of ent-16-kauren-19-oic aicd (31) into ent-16α-kaurane-17, 19-dioci acid (32).