RADIOSYNTHESIS OF [TETRAZOYL-C-11]IRBESARTAN, A NONPEPTIDIC ANGIOTENSIN-II ANTAGONIST

With the aim of visualizing myocardial angiotensin II receptors (AT1 s ubtypes), l)methyl]-4-spirocyclo-pentane-2-imidazoline-5-one ([tetrazo yl-C-11]irbesartan (SR47436/BMS-186295)) 11 was synthesized in one pot in four steps from [C-11]hydrogen cyanide. The labelling process whic h yielded [tetrazoyl-C-11]irbesartan is described in detail and could be applied to the labelling of other ligands which possess the (1H-tet razol-5-yl) moiety. Positron emission tomography (PET) studies were pe rformed in dogs. Heart, lung and blood time-activity curves did not ch ange. Therefore this new radioligand is not suitable for studying myoc ardial angiotensin II receptors with PET.