Strukturelle Abwandlungen am Vitamin D 3 . 3. Mitteilung [1]. Synthese und eigenschaften von SO 2 ‐addukten des (5 Z )‐ und (5 E )‐vitamins D 3

Structural Modifications of Vitamin D 3 . Synthesis and Properties of the SO 2 ‐Adducts with (5 Z )‐ and (5 E )‐Vitamin D 3 Treatment of (5 Z )‐ and (5 E )‐vitamin D 3 ( 4 ) with sulfur dioxide yields each quantitatively the cyclic sulfones 1a and 1b . Thermally induced elimination of sulfur dioxide leads to either isotachysterol 3 ( 3 ) alone or mixtures of isotachysterol 3 ( 3 ) and isovitamin D 3 ( 2 ). On the other hand the extrusion of SO 2 can be brought about by means of KOH/CH 3 OH or on an alumina surface affording (5 E )‐vitamin D 3 ( 4 ). On treatment with CD 3 UD/ t BuOK/D 2 O 1a and 1b are transformed (5 E )‐6, 19, 19′‐trideuteriovitamin D 3 ( 4a ).