[1] ALAIN DAUGAN. The Discovery of Tadalafil: A Novel and Highly Selective PDE5 Inhibitor. 2: 2,3,6,7,12,12a-hexahydropyrazino[1‘,2‘:1,6]pyrido[3,4-b]indole-1,4-dione Analogues[J]. Journal of Medicinal Chemistry, 2003. DOI:
10.1021/jm0300577.
[2] SHI X X, LIU S, XU W Z, et al. Highly stereoselective Pictet–Spengler reaction of d-tryptophan methyl ester with piperonal: convenient syntheses of Cialis (Tadalafil), 12a-epi-Cialis, and their deuterated analogues[J]. Tetrahedron-asymmetry, 2008, 19: 435-442. DOI:
10.1016/J.TETASY.2007.12.017.
[3] ZHANG Y, HE Q, DING H, et al. IMPROVED SYNTHESIS OF TADALAFIL[J]. Organic Preparations and Procedures International, 2005, 37: 102-199. DOI:
10.1080/00304940509355408.