Investigation on the phototransformation of tadalafil in aqueous media. 6-Epimerization vs. solvent trapping reaction.
Irradiation of tadalafil at lambda > 290 nm in aqueous solutions leads to 6-epimer and/or water adducts depending on concentration and pH. A rationalization of the results involves the heterolytic cleavage of C6-N5 bond via a well-stabilized zwitterionic intermediate. The drug is stable in the dark except under strongly basic conditions where it undergoes C12a-epimerization.
Temussi
Fabio
F
IC-REACH Dipartimento di Chimica Organica e Biochimica, Università Federico II, Complesso Universitario Monte S. Angelo, Via Cinthia 4, I-80126, Napoli, Italy. ftemussi@unina.it
Bassolino
Giovanni
G
Cermola
Flavio
F
DellaGreca
Marina
M
Iesce
Maria Rosaria
MR
Montanaro
Sara
S
Previtera
Lucio
L
Rubino
Maria
M
D002243:Carbolines / Q000737:chemistry* / Q000528:radiation effects; D002384:Catalysis; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy; D012997:Solvents / Q000737:chemistry*; D013237:Stereoisomerism; D000068581:Tadalafil; D014466:Ultraviolet Rays; D014867:Water / Q000737:chemistry*
D002243:Carbolines; D012997:Solvents; D014867:Water; D000068581:Tadalafil