Total Synthesis of the Lycorenine-Type Amaryllidaceae Alkaloid (.+-.)-Clivonine via a Biomimetic Ring-Switch from a Lycorine-Type Progenitor.

A fully diastereoselective total synthesis of the lycorenine-type Amaryllidaceae alkaloid (±)-clivonine (19) is reported via a route that employs for the first time a biomimetic ring-switch from a lycorine-type progenitor, thereby corroborating experimentally the biogenetic hypothesis first expounded for these compounds by Barton in 1960.