Discovery of Spiro[cyclohexane-dihydropyrano[3,4-b]indole]-amines as Potent NOP and Opioid Receptor Agonists

We report the discovery of spiro[cyclohexane-pyrano[3,4-b]indole]-amines, as functional nociceptin/orphanin FQ peptide (NOP) and opioid receptor agonists with strong efficacy in preclinical models of acute and neuropathic pain. Utilizing 4-(dimethylamino)-4-phenylcyclo-hexanone 1 and tryptophol in an oxa-Pictet–Spengler reaction led to the formation of spiroether 2, representing a novel NOP and opioid peptide receptor agonistic chemotype. This finding initially stems from the systematic derivatization of 1, which resulted in alcohols 3–5, ethers 6 and 7, amines 8–10, 22–24, and 26–28, amides 11 and 25, and urea 12, many with low nanomolar binding affinities at the NOP and mu opioid peptide (MOP) receptors.