The dried scent glands of the Canadian beaver, known as castoreum, contain a complex mixture of nupharamine alkaloids. Now, Horst Kunz and colleagues at the University of Mainz, Germany, have used total synthesis to determine the stereochemistry of one of these compound, 5-(3'-furyl)-8-methylindolizidine. Beavers use their fat- and pheromone-containing gland secretions to groom their fur and to mark their territory. The same secretions were used in traditional medicine, although salicylic acid is considered the only major component with physiological activity. Nevertheless, the complexity and molecular diversity of minor components have potential as possible lead compounds in drug discovery.