Total Synthesis of (±)-Gelsemoxonine

Abstract

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.