The first synthesis of tadalafil 1 (Cialis) from l-tryptophan is described. The title compound 1 was synthesized via seven steps from l-tryptophan methyl ester hydrochloride in 42.3% overall yield. Two characteristic steps involved in this synthesis are the base-catalyzed epimerization of the C-3 position of (1S, 3S)-1, 2, 3-trisubstituted-tetrahydro-β-carboline 3a and the acid-catalyzed epimerization of the C-1 position of (1S, 3R)-1, 3-disubstituted- ...