An expected two fold Peterson olefination process occurred upon the treatment of ketone 8 with TMSCH2Li followed by a treatment with p-toluenesulfonic acid in methanol, furnishing the natural product plecarpenene in 69% isolated yield. Alternatively, we also realized the total synthesis of plecarpenone via the base promoted epimerization of the C5 stereo-center followed by a desilylation. The natural product plecarpenone was successfully produced in 96% yield by two steps. All the spectroscopic data ( 1 H and C NMR, HRMS) of synthetic plecarpenene and plecarpenone were in good agreement with those previously reported by Snapper group. Figure . Synthesis of the cores of echinopines and total syntheses of plecarpenene and plecarpenone.