4-Hydroxy-3-methoxymethamphetamine
4-Hydroxy-3-methoxymethamphetamine (HMMA) is an active metabolite of 3,4-methylenedioxymethamphetamine (MDMA). It is a slightly more potent stimulant than MDMA in rodents.
Source: Wikipedia — 4-Hydroxy-3-methoxymethamphetamine (CC BY-SA 4.0)