An Efficient Formal Synthesis of the Sesquiterpenoid Longifolene

Through a convenient ring expansion reaction of key intermediate 1, enone 5, containing the longifolene skeleton, was produced. Elaboration of 5 via hydrogenation, Wittig reaction, Simmons-Smith reaction, and subsequent hydrogenolysis led to ketone 9. Reductive debromination of 9 afforded 10, the penultimate precursor to longifolene. This formal total synthesis was accomplished in 13 steps using commercially available Wieland-Miescher ketone as the starting material.