N-methyl-3-(1-hydroxy-5-[I-123]iodopent-4-enyl)-4-acetoxypiperidine, a novel candidate of acetylcholinesterase activity imaging agent

A novel acetylcholine radioanalog, N-methyl-3-(1-hydroxy-5-[I-123]iodopent- 4-enyl)-4-acetoxypiperidine, was prepared by radioiodination of the corresp onding tributylstannyl precursor that was synthesized in eight steps from 4 -piperidone. The tracer has three asymmetric carbons giving eight optical i somers. Two optical isomers were isolated in the precursor synthesis by dia stereomeric and enantiomeric separation. In the incubation experiments usin g rat cerebral cortical homogenate, one optical isomer was hydrolyzed by ac etylcholinesterase with high reactivity and selectivity. The tracer is a ca ndidate for mapping cerebral regional acetylcholinesterase activity by sing le photon emission computed tomography.