Synthesis and 11C-Radiolabelling of a Tropane Derivative Lacking the 2β Ester Group: A Potential PET-Tracer for the Dopamine Transporter

Article abstract of DOI:10.1002/(SICI)1099-1344(199905)42:5<447::AID-JLCR204>3.0.CO;2-9

The synthesis and 11C-radiolabelling of a new tropane analogue, 3β-(4'-chlorophenyl)-2β-(3'-phenylisoxazol-5'-yl)tropane (β-CPPIT), an inhibitor of the dopamine transporter, is reported. The desmethyl compound, 3β-(4'-chlorophenyl)-2β-(3'-phenylisoxazol-5'-yl)nortropane (5) was prepared via a six-step reaction sequence starting from cocaine. [11C]-β-CPPIT was labelled by N-methylation using [11C]-methyl iodide obtained from the gas phase reaction of [11C]-methane with iodine in 60 +/- 10 percent radiochemical yield (decay corrected from [11C]-methyl iodide). The overall synthesis time was on average 60 minutes at EOB (end of bombardment). The final product had a specific activity of 2000 - 2700 Ci/mmol (74 - 100 TBq/mmol) at EOS (end of synthesis) and the radiochemical purity was greater than 99 percent. [11C]-β-CPPIT showed a logP value of 2.1 indicating that a free diffusion through the blood-brain-barrier should be possible.