Transformation of alcohol
4 to
![](/images/gifchars/alpha.gif)
-azidoketone
6, a hexacyclic steroid bearing the requisite functionalityand spiroketal stereochemistry of the symchiral South portion of cephalostatin 7 (
10) is described. Reaction ofa 1:1 mixture of
![](/images/gifchars/alpha.gif)
-azidoketones
5 and
6 with sodium hydrogen telluride is followed by cleavage of the protectinggroups cephalostatin 12 (
9), cephalostatin 7 (
10), and ritterazine K (
11).