Incaniline (isoargentatin A) from Parthenium argentatum

The title compound, (20S,24R)-incanilin, C₃₀H₄₈O₄, contains three six-membered rings and two five-membered rings. The six-membered ring B adopts a distorted envelope conformation and five-membered ring D adopts a twist conformation. In the crystal structure, the mol­ecules exist as O—H...O hydrogen-bonded dimers.