Stereocontrolled Total Synthesis of (±)-Culmorin via the Intramolecular Double Michael Addition

We have accomplished the total synthesis of (±)-culmorin from the readily available ketone (11 steps, 46% overall yield). The tricyclo[6.3.0.0 3,9 ]undecan-10-one skeleton, the culmorin framework, was constructed via the intramolecular double Michael addition of the cyclopentenone having an α,β-unsaturated ester moiety by using LHMDS. The stereochemistry of newly generated four stereogenic centers was perfectly controlled by the reaction.