Total Synthesis of (±)-Gelsemoxonine

Gelsemoxonine (1) is a Gelsemium alkaloid
incorporating an unusual azetidine. Its total synthesis was achieved
employing a novel ring contraction of a spirocyclopropane isoxazolidine
to furnish a β-lactam intermediate. This β-lactam ring
was further elaborated into the azetidine of Gelsemoxonine. In addition,
the synthesis includes a highly diastereoselective reductive Heck
cyclization for the installation of the oxindole ring system as well
as a directed hydrosilylation of an alkyne to access the ethyl ketone
of the natural product.