A Simple Synthesis of a Model of the Tetracyclic Bisketal Lactone Mainframe of Saudin

The partial structure 2 of the bisketal-type, tetracyclic saudin (1), an important natural product, was de novo synthesized. A key step was the Jones oxidation of the epoxide 3, which gave rise to epoxide-ring opening, followed by acetal hydrolysis, alcohol oxidation, and, finally, intramolecular acetal formation. The resulting key intermediate was finally oxidized to the target lactone 2.