2,5-Dimethoxy-3-bromoamphetamine, also known as 3-Br-2,5-DMA, 3-DOB, or iso-DOB, is a psychoactive compound belonging to the family of substituted phenõthylamines and amphetamine derivatives. It is a positional isomer of 4-bromo-2,5-dimethoxyamphetamine (DOB; 4-Br-2,5-DMA) and a derivative of 2,5-dimethoxyamphetamine (2,5-DMA; DOH) where the hydrogen atom in the 3 position of the benzene ring is replaced by bromine. 3-Br-2,5-DMA exhibits agonistic activity against serotonin 5-HT<sub>2</sub> and 5-HT<sub>3</sub> receptors. In The Shulgin Index, 3-Br-2,5-DMA was referred to as "3-DOB"
3-Br-2,5-DMA demonstrated weak or even low psychoactivity, unlike its isomers, and did not have a significant effect on the activity of neurons in the locus coeruleus. Despite the structural difference, it is precisely because of the positional difference from other isomers that this substance exhibits a low psychoactive effect, 3-Br-2,5-DMA It did not cause any behavioral changes or hallucinogenic effects, it is noted that this substance is of "inactive". 3-Br-2,5-DMA binds to serotonin receptors approximately 50 to 60times weaker than DOB.
3-Br-2,5-DMA can be successfully obtained from nitropropene. Synthesis of the 3-Br-2,5-DMA requires the use of aluminum hydride (AlH<sub>3</sub>) instead of the standard lithium aluminum hydride, since the latter causes a dehalogenation side reaction leading to the elimination of a bromine atom.
3-DOB was first described in the scientific literature by Richard Glennon and colleagues by 1980.