Complex sentence: Antommarchi left Florence for Saint Helena to become Napoleon Bonaparte I's physician until his death at the behest of Napoleon's mother Maria Letizia Ramolino and his uncle Cardinal Joseph Fesch.
Split into simpler sentences: Antommarchi left Florence for Saint Helena to become Napoleon I's physician until his death. Antommarchi took up this position at the behest of Napoleon's mother Maria Letizia Ramolino and his uncle Cardinal Joseph Fesch.