7-Methylindole-3-carboxaldehyde is a reactant for preparation of tryptophan dioxygenase inhibitors pyridyl-ethenyl-indoles as potential anticancer immunomodulators, antibacterial and antituberculosis agents, antiandrogens effective against androgen receptor mutants, anti-bovine viral diarrhea virus (BVDV) agents, receptor subtype 5 antagonists, glucocorticoid receptor ligands, necroptosis inhibitors, and orally efficacious small-molecule activator of the insulin receptor.