The tricarboxylic acid named in the title, originally derived from abietic acid, and which was a key degradation product of other diterpenoid resin acids, has been synthesised from bicyclo[3,3,1]nonane intermediates. The route unambiguously defines the stereochemistry at the three adjacent asymmetric centres. Attempts to convert suitably substituted derivatives of 3-oxabicyclo[3,3,1]nonane into the same acid are also described.