4-(3-Phenylpropyl)-2,5-dimethoxyamphetamine (DOPP or DOPhPr), also known as 4-PhPr-2,5-DMA, is a serotonin receptor modulator of the phenethylamine, amphetamine, and DOx families. The properties and effects of 4-PhPr-2,5-DMA in humans do not appear to be known. It shows high affinity for both the serotonin 5-HT<sub>2A</sub> and 5-HT<sub>2C</sub> receptors and acts as a weak partial agonist or antagonist of the serotonin 5-HT<sub>2A</sub> receptor. The drug has lower affinity for the serotonin 5-HT<sub>2A</sub> receptor than its closely related positional isomer 4-PhPr-3,5-DMA. This is an apparent reversal of the usual situation with DOx and related drugs, in which the 2,5-dimethoxy pattern is optimal for serotonin 5-HT<sub>2A</sub> receptor interactions. 4-PhPhr-2,5-DMA was first described in the scientific literature by Richard Glennon and colleagues by 1989.