Preparation of carbon‐11 labelled prazosin, a potent and selective α1‐adrenoreceptor antagonist

The α1-adrenoreceptor antagonist, Prazosin : 2-[4-(2-furoyl) piperazin-1-yl]-4-amino-6,7-dimethoxyquinazoline, has been labelled with carbon-11 for in vivo studies of α1-adrenoreceptors using positron emission tomography. The preparation of [2-11C] furoyl chloride, from cyclotron-produced [11C] carbon dioxide, and its reaction with the secondary amine, 2-(piperazin-1-yl)-4-amino-6,7-dimethoxyquinazoline, provides a fast (35 min) route to carbon-11 labelled prazosin in high radiochemical yield (30-40 %, decay-corrected) with high specific activity (26-37 GBq/μmol, 0.7-1.0 Ci/μmol).