The enantioselective synthesis of (+)-17-norcharaciol is described. An uncatalyzed intramolecular carbonyl-ene reaction and a ring-closing metathesis were used as key C/C-connecting transformations to assemble the trans-bicyclo[10.3.0]pentadecane norditerpenoid core. We also report the evolution of our synthetic strategy toward the fully substituted characiol skeleton and the experiences from this venture.

[reaction: see text] A scalable enantioselective synthesis of the nonnatural 17-norjatrophane diterpene 3-propionyl-15-acetyl-17-norcharaciol is described. Key C/C-connecting transformations are an Evans aldol reaction, an intramolecular carbonyl ene reaction, a Horner-Wadsworth-Emmons olefination, and a ring-closing metathesis for the formation of a 12-membered carbacycle.

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A convergent synthesis of the CDE and CDEF ring systems of pectenotoxin-2 from C and F ring precursors is described.