Improved synthesis and radiolabeling of [11C]MP4A, a suitable ligand for the investigation of the cholinergic system using PET.

An improved synthesis of the precursor acetic acid-piperidine-4-yl ester by acetylation of 4-hydroxypiperidine hydrochloride in anhydrous chloroform was developed. A procedure for fast evaluation and characterization of products originated by acetylation of the 4-piperidinol using LC-APCI/MS with an acetonitrile-water gradient method on a Merck Purosphere RP-18 column was also developed. The highly purified precursor allowed the production of [11C]MP4A for PET studies of acetylcholine neurotransmission system. The tracer was produced with >98% radiochemical purity, with yields ranging 20-60% (decay-corrected) from EOB.