To seek broader applications of our methodology, the highly strained cis-fused bicyclic core of echinopines, isolated from the root of the plant Echinops spinosus in 2008, was synthesized using this reaction (Figure ). Biosynthetically, echinopines A and B were proposed to originate from a guanine type precursor through a series of rearrangements. Inspired by the biosynthetic pathway, the phenyl ether derivative of 3n was easily transformed into the corresponding ketone 9. Then a reduction of the α,β-unsaturated ester group of 9 by palladium-catalyzed hydrogenation reaction generated a pair of diastereomers 10 and C8-epi-10 in 71% and 14% yield respectively. Treatment of the ketone 10 with a Wittig reaction provided the lactone 11 and the olefine 12 in 72% overall yield (dr 3:1), which contained the core moiety of guanine type triterpenoids with a highly strained cis-fused bicyclo[5.3.0]decane ring system. The similar intermediate was reported by Liang and coworkers previously. Table . Screening of conditions for the reduction a a Isolated yields, reactions ran on 0.012 mmol scale unless otherwise specified. b Reaction ran on 1.0 mmol scale.