Synonyms: cis-ent-Tadalafil;(6S,12aR)-;Tadalafil IMpurity: IMpurity F;Tadalafil EP IMpurity C (cis-ent-tadalafil);Tadalafil IMpurity E (6S, 12R);(6S,12aR)-6-(1,3-benzodioxol-5-yl)-2-Methyl-2,3,6,7,12,12a-hexahydropyrazino[1′,2′:1,6]pyrido[3,4-b]indole-1,4-dione;Tadanafil EP or USP impurity C