Development of [11C]L-159,884: A radiolabelled, nonpeptide angiotensin II antagonist that is useful for angiotensin II, AT1 receptor imaging

[11C]L-159,884 ([11C] N-[[4′[(2-ethyl-5,7-dimethyl-3H-imidazo[4,5-b]pyridin-3-yl) methyl][1,1′- biphenyl]-2-yl]sulfonyl]-4-methoxybenzamide) and [11C]L-162, 574 ([11C] N-[[4′[2-ethyl-5,7-dimethyl-3H-imidazo[4,5-b]pyridin-3-yl)methyl][1,1′- biphenyl]-2-yl]sulfonyl]-3-methoxybenzamide), b both potent and selective ligands for the AT1 receptor, were prepared by C-11 methylation of the corresponding desmethyl phenolic precursors. The radiotracers were purified by semi-preparative reverse-phase HPLC. Non-decay corrected radiochemical yields were 5 and 3% for L-159,884 and L-162,574 respectively, and the average specific activity was 2979 mCi/μmol at end-of-synthesis (EOS). The average time of synthesis was 18 min.