Structure and photochemical behavior of the cyclodextrin inclusion complexes of the benzoylthiophene-derived drugs tiaprofenic acid (=5-benzoyl-alpha-methylthiophene-2-acetic acid) and suprofen (=alpha-methyl-4-(2-thienylcarbonyl)benzeneacetic acid)

The effect of beta -cyclodextrin (beta -CD) on the excited-state reactivity of the two benzoylthiophene derivatives, tiaprofenic acid (TPA; 2) and suprofen (SPF; 3) in their carboxylate forms is studied. The presence of beta -cyclodextrin does not affect the nature of the photoproduced transients and the photoproducts, but increases the photodegradation quantum yields of both drugs. The efficiency of the photodecarboxylation process is enhanced. This effect is rationalized in the light of the inclusion of 2 and 3 in the beta -CD cavity, affecting the energy of the lowest excited states of the drugs. The structure of the complexes is determined by induced circular dichroism. and molecular-mechanics and dynamic Monte Carlo calculations. The photoreactivity of the decarboxylated photoproduct 7 of tiaprofenic acid (2) in presence of beta -CD is also examined. RI Monti, Sandra/B-9272-2009; Sortino, Salvatore/E-4684-2011