Facile synthesis of [11C]buprenorphine for positron emission tomographic studies of opioid receptors.

We have developed a simple and rapid method for the production of buprenorphine (BPN), a potent opioid partial agonist, labelled with carbon-11 at the 6-methoxy position. The procedure uses a precursor synthesized in high yield (89%) from BPN in two steps and employs [11C]iodomethane as the radiolabelling reagent. [11C]BPN of 97% radiochemical purity can be prepared in high specific activity (41 GBq/mumol; 1120 mCi/mumol) in a radiochemical yield of 10% at end-of-synthesis (not decay corrected). The [11C]BPN is available for use in studies of cerebral opioid receptors by positron emission tomography within 24 min from end-of-bombardment, including radiosynthesis, purification, formulation for i.v. injection and determination of specific activity.