Strukturelle Abwandlungen am Vitamin D3. 3. Mitteilung [1]. Synthese und eigenschaften von SO2‐addukten des (5Z)‐ und (5E)‐vitamins D3

Structural Modifications of Vitamin D3. Synthesis and Properties of the SO2‐Adducts with (5Z)‐ and (5E)‐Vitamin D3 Treatment of (5Z)‐ and (5E)‐vitamin D3 (4) with sulfur dioxide yields each quantitatively the cyclic sulfones 1a and 1b. Thermally induced elimination of sulfur dioxide leads to either isotachysterol3 (3) alone or mixtures of isotachysterol3 (3) and isovitamin D3 (2). On the other hand the extrusion of SO2 can be brought about by means of KOH/CH3OH or on an alumina surface affording (5E)‐vitamin D3 (4). On treatment with CD3UD/tBuOK/D2O 1a and 1b are transformed (5E)‐6, 19, 19′‐trideuteriovitamin D3 (4a).