Tiamulin Hydrogen Fumarate Imp.E (EP) as Fumarate salt: (3aS,4R,6S,8R,9R,9aR,10R)-6-ethenyl-4,6,9,10-tetramethyl-1,5-dioxodecahydro-3a,9-propano-3aH-cyclopentacycloocten-8-yl [[2-(diethylamino)ethyl]sulfanyl]acetate fumarate (11-oxotiamulin).