Spinosyn A is the major component of a complex of unusual, hydrophobic macrocyclic lactones isolated from Saccharopolyspora spinosa in 1991. The 12-membered macrocyclic lactone is fused to form a rare 12-5-6-5 tetracyclic ring system, with the macrocycle and the terminal cyclopentane bearing glycosides. Spinosyn A is a potent insecticide for crop pathogens and ectoparasite control on animals. The spinosyns have a unique mechanism of action involving disruption of nicotinic acetylcholine receptors.