J. Org. Chem. 23(12), 1979-1984 (1958) (https://www.thevespiary.org/rhodium/Rhodium/pdf/activity.of.subst.peas.in.cats.pdf)
(https://www.thevespiary.org/rhodium/Rhodium/pdf/activity.of.subst.peas.in.cats.pdf) 3,5-Dimethoxyphenethylamine is completely devoid of entheogenic effects in a study made on cats. It can probably be assumed that the 3,5-Dimethoxyamphetamine analog isn't that fun either.Post 370205 (https://www.thevespiary.org/talk/index.php?topic=12393.msg37020500#msg37020500)
(GPig2: "4-isobutyl-3,5-dimethoxy-PEA = POISON", Serious Chemistry) I wondered whether other 4th position substitutes may have been tried. I don't really understand why the 3,5-methoxy amines would be thought to be µ opioid antagonists, but then again my SAR knowledge is somewhat limited.