Total Synthesis of Isodihydrokoumine, (19<i>Z</i>)‑Taberpsychine, and (4<i>R</i>)‑Isodihydroukoumine <i>N</i>₄‑Oxide

We report the total synthesis of the natural products isodihydrokoumine and (19Z)-taberpsychine in 11 steps each and (4R)-isodihydrokoumine N4-oxide in 12 steps from commercially available starting materials. The key reactions include an intramolecular [3 + 2] nitrone cycloaddition and Lewis acid mediated cyclizations of a common intermediate to provide the core structures of either taberpsychine or isodihydrokoumine.