Synthesis of sidisterone, a phytoecdysteroid from Silene dioica (L.) Clairv.

The first synthesis of the natural phytoecdysteroid sidisterone is realized. It is based on the isoxazoline ring reductive cleavage of 20-hydroxy-20-isoxazolynylecdysterone, acid-catalyzed cyclization of the resultant ketodiol into a dihydrofuran derivative, and ozonolysis of the exocyclic double bond of the latter.