Synthesis of carbon-11-labeled aminoalkylindole derivatives as new candidates of cannabinoid receptor radioligands for PET imaging of alcohol abuse.

Carbon-11-labeled aminoalkylindole derivatives (1-butyl-7-[(11)C]methoxy-1H-indol-3-yl)(naphthalene-1-yl)methanone ([(11)C]3), 1-butyl-7-[(11)C]methoxy-3-(naphthalene-1-ylmethyl)-1H-indole ([(11)C]5), and 1-butyl-7-[(11)C]methoxy-3-(naphthalene-2-yl)-1H-indole ([(11)C]8) were prepared by O-[(11)C]methylation of their corresponding precursors with [(11)C]CH3OTf under basic condition (2N NaOH) and isolated by a simplified solid-phase extraction (SPE) method in 50-60% radiochemical yields based on [(11)C]CO2 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.