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 selective 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 30 minutes.