SYNTHESIS AND CHARACTERIZATION OF 7-ALPHA-O-IODOALLYL DIPRENORPHINE -A NEW LIGAND FOR POTENTIAL SPECT IMAGING OF OPIOID RECEPTORS

The preparation and synthesis of [I-125]7 alpha-O-iodoallyl diprenorph ine, a high affinity opioid receptor antagonist, is described using a versatile vinylstannane as prosthetic group for radioiodination at the tertiary alcohol group in the 7 alpha-side chain. Radioiododestannyla tion with selective conditions in one step occurs under mild, no-carri er-added-conditions to give the corresponding [I-125]7 alpha-O-iodoall yl diprenorphine analogue in good radiolabelled yields (70-90%) with s pecific radioactivity 80 TBq/mmol (2200 Ci/mmol) and radiochemical pur ity >95%. Iodoallyl diprenorphine exhibited in vitro a very high affin ity (K-i=0.4 nM), so that this radioligand could be suitable for imagi ng opioid receptors in living humans by Single Photon Emission Compute d Tomography (SPECT).