Rearrangement pathways in the bicyclo[4.4.1]undecane ring system

The readily available bicyclo[4.4.1]undecane ring system can be transformed into the isomeric bicyclo[5.3.1]undecane and bicyclo[5.4.0]undecane systems via related rearrangement pathways. The resultant products constitute the AB ring substructure of the taxane diterpenes and the BC ring substructure of the tigliane diterpenes, respectively.