Synthesis of J-113397, the first potent and selective ORL1 antagonist

The first potent and selective small molecule ORL1 antagonist 1-[(3R,4R)-1-cyclooctylmethyl-3-hydroxymethyl-4-piperidyl]-3-ethyl-1,3-dihydro-2H-benzimidazol-2-one (J-113397) was synthesized. J-113397 is the only available potent and selective ORL1 antagonist, which is a very useful pharmacological tool for elucidating the physiological roles of the nociceptin–ORL1 system. J-113397 was synthesized from ethyl 4-oxo-3-piperidinecarboxylate and a coupling reaction of 2-fluorobenzene with 4-amino-ethoxycarbonylpiperidine is a key step.