Synthesis of carbon-11-labeled imidazopyridine- and purine-thioacetamide derivatives as new potential PET tracers for imaging of nucleotide pyrophosphatase/phosphodiesterase 1 (NPP1).

The target tracer carbon-11-labeled imidazopyridine- and purine-thioacetamide derivatives, N -(3-[ 11 C]methoxy-4-methoxyphenyl)-2-((5-methoxy-3 H -imidazo[4,5- b ]pyridin-2-yl)thio)acetamide (3-[ 11 C] 4a ) and N -(4-[ 11 C]methoxy-3-methoxyphenyl)-2-((5-methoxy-3 H -imidazo[4,5- b ]pyridin-2-yl)thio)acetamide (4-[ 11 C] 4a ); 2-((6-amino-9 H -purin-8-yl)thio)- N -(3-[ 11 C]methoxy-4-methoxyphenyl)acetamide (3-[ 11 C] 8a ) and 2-((6-amino-9 H -purin-8-yl)thio)- N -(4-[ 11 C]methoxy-3-methoxyphenyl)acetamide (4-[ 11 C] 8a ), were prepared by O -[ 11 C]methylation of their corresponding precursors with [ 11 C]CH 3 OTf under basic condition (2 N NaOH) and isolated by a simplified solid-phase extraction (SPE) method in 50–60% radiochemical yields based on [ 11 C]CO 2 and decay corrected to end of bombardment (EOB). The overall synthesis time from EOB was 23 min, the radiochemical purity was >99%, and the specific activity at end of synthesis (EOS) was 185–555 GBq/μmol. [ABSTRACT FROM AUTHOR]