A Novel Bromine-Induced Ring Expansion of the Spiroimine Moiety of the Shellfish Toxin Gymnodimine

Treatment of the shellfish toxin gymnodimine with one equivalent of molecular bromine at -78 °C resulted in stereoselective formation of a novel ring-expansion product. Participation of the spiromine unit in this novel bromine-induced ring expansion reaction provides insight into how the reactivity of spiroimine moiety may contribute to the toxicity of this marine biotoxin when activated by the presence of an appropriate environmental electrophile.