Fig. 1
Zilpaterol, Clenbuterol and Albuterol, structurally related β2-agonists: Zilpaterol, ( ±)-trans-4,5,6,7-Tetrahydro-7-hydroxy-6-(isopropylamino)-imidazo[4,5,1-jk]-[1]benzazepin-2(1H)-one, formula, C14H19N3O2, molar mass 261.325 g/mol. Zilpaterol contains two chiral carbons, carbons 6 and 7, giving rise to four enantiometic forms of Zilpaterol, (6R,7R), (6R,7S), (6S,7R). (6S,7S). Zilpaterol is marketed as Zilmax [3], a racemic mixture of the pharmacologically active 6R,7R eutomeric β2-agonist isomer and also the 6S,7S enantiomer.