An Expeditious Synthesis of the Dendrobatid Indolizidine Alkaloid 167B

The synthesis of the racemic title alkaloid 1 has been accomplished in eight steps and 7.2% overall yield from pyrrolidine-2-thione (5) and ethyl hex-2-enoate (6). Key steps include a ring closure that takes advantage of the nucleophilicity of a vinylogous urethane 8, and stereoselective reduction of the C=C double bond of a bicyclic vinylogous amide 12.

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