Synthesis of Spin-Labelled Derivative of 2-(4-Isobutylphenyl)propionic Acid (Ibuprofen)

Conjugates of drugs and biologically active compounds with stable nitroxides are often used to study pharmacokinetics, the biochemical mechanisms of activity and distribution of the active substance in body tissues using electron paramagnetic resonance and magnetic resonance imaging. In this work, we synthesised a paramagnetic analogue of ibuprofen, a known cyclooxygenase inhibitor, retaining the free carboxyl group for critical interaction with the active site of this enzyme. For this purpose, ibuprofen was subjected to nitration into the aromatic ring, the nitro group was reduced, and the resulting amine was acylated with 2,2,5,5-tetramethyl-3-pyrroline-1-oxyl-4-carboxylic acid chloride.