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 sup rofen (SPF; 3) in their carboxylate forms is studied. The presence of beta -cyclodextrin does not affect the nature of the photoproduced transients an d the photoproducts, but increases the photodegradation quantum yields of b oth 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 dic hroism. and molecular-mechanics and dynamic Monte Carlo calculations. The p hotoreactivity of the decarboxylated photoproduct 7 of tiaprofenic acid (2) in presence of beta -CD is also examined.