Di­methyl 6‐methoxy‐4aβ‐methyl‐9‐oxo‐1,2,3,4,4a,9,10,10aβ‐octa­hydro­phenanthrene‐1,1‐di­carboxyl­ate

In the title tricyclic keto‐diester, C₂₀H₂₄O₆, a potential intermediate in the synthesis of bioactive podocarpic acid, the outer cyclo­hexane ring (in a chair conformation) is cis fused to the central cyclo­hexanone ring (in a half‐chair conformation). The conformational analysis of the compound, investigated by semi‐empirical quantum mechanical AM1 calculations, shows a good agreement with the X‐ray structure, except for the orientation of the methyl, methoxy­phenyl and methoxy­carbonyl substituents.