The 14-dehydration- and 14-H derivatives of the orexin 1 receptor (OX1R) antagonist YNT-707 (2) were synthesized. The obtained derivatives showed higher affinities for OX1R than the corresponding 14-hydroxy derivatives. The conformational analysis suggested that the 17-sulfonamide groups in the derivatives without the 14-hydroxy group have a greater tendency to be oriented toward the upper side of the D-ring compared with the 14-hydroxy derivatives. Additionally, the 14-dehydration-derivative with 6α-amide side chain showed significantly higher affinity than the 14-hydroxy derivative, while the corresponding 14-H derivative showed only slightly higher affinity. Thus, the 14-hydroxy group strongly affects the affinity of the antagonist for the OX1R.
Keywords: 4,5-Epoxymorphinan; Conformational study; OX1R antagonist; Orexin; YNT-707.
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