(6R,12aS)-N-Desmethyl ent-Tadalafil929100-66-3171488-04-3(6R,12aS)-6-(1,3-Benzodioxol-5-yl)-2,3,6,7,12,12a-hexahydropyrazino[1',2':1,6]pyrido[3,4-b]indole-1,4-dione; Tadalafil EP Impurity A N-Desmethyl Impurity;Pyrazino[1',2':1,6]pyrido[3,4-b]indole-1,4-dione, 6-(1,3-benzodioxol-5-yl)-2,3,6,7,12,12a-hexahydro-, (6R,12aS)-rel-Pyrazino[1',2':1,6]pyrido[3,4-b]indole-1,4-dione,6-(1,3-benzodioxol-5-yl)-2,3,6,7,12,12a-hexahydro-,(6R,12aS)-rel-