Application： 4-Nitroindole was used in the synthesis of 1,3,4,5-tetrahydropyrrolo-[4,3,2-de]quinoline. Reactant for preparation of: Tryptophan dioxygenase inhibitors pyridyl-ethenyl-indoles as potential anticancer immunomodulators Meridianin derivatives as protein kinase (PKC) inhibitors and vitro antiproliferative agents Anti-angiogenic agents Sodium-dependent glucose co-transporter 2 (SGLT2) inhibitors for the management of hyperglycemia in diabetes Biologically active indoles CGRP receptor antagonists Nucleosides CB2 cannabinoid receptor ligands