Pyrazole-type cannabinoid ligands conjugated with fluoro-deoxy-carbohydrates as potential PET-imaging agents: Synthesis and CB1/CB2 receptor affinity evaluation

A novel class of cannabinoid ligands was synthesized in good overall yields by means of oxime-bio-conjugation between hydroxylamine-functionalized Rimonabant-type pyrazoles and fluoro-deoxy-carbohydrates (d-2-fluoro-deoxy-glucose, FDG, and d-5-fluoro-5-deoxy-ribose, FDR). FDR proved to be superior to FDG for bio-conjugation, as it occurred in milder conditions and at faster rate (rt, 20 min vs. 100 °C, 30 min). All of the title compounds showed relatively modest affinity for the CB1 receptor (high nanomolar range) and selectivities vs. the CB2.