Alternative Synthesis of Tadalafil: PDE5 Inhibitor.

Abstract Two-step alternative synthesis of tadalafil (1) is described. The synthesis features Pictet–Spengeler type reaction and DCC (N,N′-dicyclohexylcarbodiimide)/HOBt (N-hydroxybenzotriazole)–mediated double amidation employing sarcosine ethyl ester hydrochloride.