The chemistry of thujone. XIII. Synthetic studies in the digitoxigenin series

The thujone-derived chiral synthon 1 is converted, via selenium chmistry, to the important cross-conjugated dienone 2 and the latter is then convertible to the unsaturated cardenolide analogue 3, which through known methodology (3 → 26 → 27 → 4), completes a formal synthesis of digitoxigenin (4). Extensive studies to afford 2 from androstenedione (5) are also described and a new approach to elaborate the essential butenolide ring system, characteristic of the cardiac active steroids, is developed. Keywords: thujone, steroid synthesis, digitoxigenin.