Synthesis of the Core Ring System of the Antiosteoporotic Citrofulvicin.

Synthesis of the octacyclic ring system of citrofulvicin is described in nine steps from readily available starting materials. Blocking undesired intramolecular cyclization of a reactive β-diketone intermediate by transient incorporation of a dithiolane ring led to the formation of the requisite 1-hydroxy-2,4,6-trioxaadamantane ring system of citrofulvicin.