Synthesis of the C/D/E and A/B Rings of Xestobergsterol-(A)

The A/B and the C/D/E rings of the xestobergsterol skeleton have been stereoselectively synthesized starting with testosterone and epiandrosterone, respectively. A deconjugative ketalization of the A-ring enone of testosterone provided a handle for functionalization of the B-ring. A stereoselective aldol condensation was used to incorporate the E-ring.