Abstract
We previously reported the total synthesis of several Teucrium clerodane diterpenoids including teucvin (1), 12-epi-teucvin (2), montanin A (3) and teuscorolide (4) in a unified Diels-Alder approach. A full account for the tactical installation of the C4-C6 furan ring of 3 from an α,β-unsaturated lactone moiety, and the elaboration of the resulting furan unit into an α,β-unsaturated γ-hydroxyl lactone for preparing 4 is discussed herein. In addition, the transformation of 3 and its 12-epimer into 1 and 2 by the air-mediated furan oxidation reaction is described.