Development of [C-11]L-159,884: A radiolabelled, nonpeptide angiotensin II antagonist that is useful for angiotensin II, AT(1) receptor imaging

[C-11]L-159,884 ([C-11] N-[[4'[(2-ethyl-5,7-dimethyl-3H-imidazo[4, 5-b]pyridin-3-yl) methyl][1,1 '-biphenyl]-2yl]sulfonyl]-4-methoxybenzamide) and [C-11]L-162,574 ([C-11] N-[[4'[2-ethyl-5,7-dimethyl-3H-imidazo[4, 5-b]pyridin-3-yl)methyl][1,1'-biphenyl]-2-yl]sulfonyl]-3-methoxybenzamide), both potent and selective ligands for the AT, 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/mu mol at end-of-synthesis (EOS). The average time of synthesis was 18 min.