Hf. Tang et al., Progress toward the total synthesis of ingenol: Construction of the complete carbocyclic skeleton, ORG LETT, 3(10), 2001, pp. 1563-1566
[GRAPHICS]
The complete carbocyclic skeleton of ingenol is assembled via a route that
employs ring-closing metathesis (RCM) to close the strained "inside outside
" BC ring system (i.e., 24 --> 25).