Discovery of highly selective κ-opioid receptor agonists: 10α-Hydroxy TRK-820 derivatives.

κ-Opioid receptor agonists with high selectivity over the μ-opioid receptor are attractive targets in the development of drugs for pain and pruritus. We previously reported the synthesis of 10α-hydroxy TRK-820 (1). In this study, we elucidated the biological properties of 1 and optimized its 6-acyl unit by modifying our synthetic route. Among the 10α-hydroxy TRK-820 derivatives prepared, 26 showed the most potent κ-opioid agonist activity (EC50 =0.00466nM) and excellent selectivity and 22 was the most κ-selective agonist.