Carbon-11 labeling of a potent, nonpeptide, AT1-selective angiotensin-II receptor antagonist: MK-996

[α-11C]Benzoyl chloride was synthesized and purified by normal phase HPLC. [11C]MK-996 ([11C]N-[[4'[(2-ethyl-5,7-dimethyl-3H-imidazo [4,5-b]pyridin-3-yl)methyl][1,1'-biphenyl]-2-yl]sulfonyl]-benzamide), a potent and selectrive ligand for the AT1 receptor, was prepared by N-benzoylation of L-159,221 with [α-11C]benzoyl chloride in tetrahydrofuran using lithium bis(trimethylsilyl)amide as a base. The radiotracer was purified by semi-preparative reverse-phase HPLC. The average specific activity was 1162 mCi/μmol calculated at end-of-synthesis (EOS). The average time of synthesis including formulation was 38 minutes. (Author)