Synthesis of (±)-Pseudotabersonine

Significance

Pseudotabersonine is a pandoline alkaloid, which are a subgroup of the Aspido­sperma alkaloids. Previous syntheses have mainly consisted of a biomimetic Diels-Alder reaction and a reduction-oxidation sequence followed by spontaneous cyclization. The double ring-closing metathesis step is a very interesting strategy retro-synthetically and, although it led mainly to the undesired diastereomer in this case, this approach may be useful for alternative natural or unnatural products.