4-Hydroxyindole is a member of the class of hydroxyindoles that is 1H-indole substituted by a hydroxy group at position 4. 4-Hydroxyindole is an important raw material or intermediate in the synthesis of pharmaceutical products and industrial polymers[1].
[1]. Nenad Manevski, et al. Glucuronidation of psilocin and 4-hydroxyindole by the human UDP-glucuronosyltransferases. Drug Metab Dispos. 2010 Mar;38(3):386-95.