The importance of the 6- and 7-positions of tetrahydroisoquinolines as selective antagonists for the orexin 1 receptor
Perrey, DA., Decker, A., Li, JX., Gilmour, B., Thomas, B., Harris, D., Runyon, S., & Zhang, Y. (2015). The importance of the 6- and 7-positions of tetrahydroisoquinolines as selective antagonists for the orexin 1 receptor. Bioorganic and Medicinal Chemistry, 23(17), 5709-5724. https://doi.org/10.1016/j.bmc.2015.07.013
Selective antagonism of the orexin 1 (OX1) receptor has been proposed as a potential mechanism for treatment of drug addiction. We have previously reported studies on the structure-activity relationships of tetrahydroisoquinoline-based antagonists. In this report, we elucidated the respective role of the 6- and 7-substitutions by preparation of a series of either 6-substituted tetrahydroisoquinolines (with no 7-substituents) or vice versa. We found that 7-substituted tetrahydroisoquinolines showed potent antagonism of OX1, indicating that the 7-position is important for OX1 antagonism (10c, Ke=23.7nM). While the 6-substituted analogs were generally inactive, several 6-amino compounds bearing ester groups showed reasonable potency (26a, Ke=427nM). Further, we show evidence that suggests several compounds initially displaying insurmountable antagonism at the OX1 receptor are competitive antagonists with slow dissociation rates
