5-Cyano-2,3-di-(p-tolyl)tetrazolium chloride is a redox dye that indicates cellular respiration activity in cells, then undergoes reduction to produce a fluorescent formazan in the presence of oxygen.

5-Cyanoindole has a variety of applications. It is used to create electropolymer films and can function as an enzyme inhibitor. Additionally, 5-cyanoindole is involved in the preparation of dihydroisoquinolines, benzoylindoles, 4,5-dihydrocyclopenta[c]quinolones, and vinyl indoles.

5-Ethylindole is a reagent used for chemical synthesis. It forms a reactant for the creation of IL2 T-cell (ITK) inhibitors and Sodium-dependent glucose co-transporter 2 inhibitors (SGLT2), along with small molecule C5a receptor modulators and the synthesis of antitumor agents.

5-Ethylindole-2-carboxylic acid is a reagent used for chemical synthesis useful for synthesizing auxin analogs and pharmaceuticals.

5-Ethylindole-3-acetic acid is an auxin analog of indole-3-acetic acid and a reagent for chemical synthesis.

5-Fluoro-DL-tryptophan is a fluorinated tryptophan analog that is capable of being incorporated into proteins. It may be incorporated into cyclic AMP receptor protein (CRP) to study ligand binding changes in E. coli. Additionally, it can serve as an internal standard in chromogenic analysis of tryptophan and other tryptophan derivatives. Metabolically, 5-fluoro-DL-tryptophan is a tryptophan antagonist.

5-Fluoro-L-tryptophan monohydrate is a tryptophan derivative incorporated into proteins during their synthesis. It is useful as a reporter group due 19F and provides a way to study enzyme mechanisms through NMR. 5-fluoro-L-tryptophan is nonspecifically cytotoxic due to malfunctioning enzymes containing 5-fluoro-Trp in place of Trp.

5-Fluorocytosine is a fluorinated cytosine analog and antifungal agent. 5-fluorocytosine becomes 5-fluorouracil and is then incorporated into RNA, causing miscoding and inhibition of DNA synthesis. It is effective against Candida and Cryptococcus species and can be used as a negative selection agent in transgenic plants.

5-Fluoroindole is a reagent involved in a variety of biochemical preparation procedures including: preparation of 5-HT6 receptor ligands, immunosuppressive agents, tryptophan dioxygenase inhibitors, anticancer agents, antibacterial agents, sodium-dependent glucose co-transporter 2 (SGLT2) inhibitors, selective serotonin reuptake inhibitors, and myeloperoxidase inhibitors.

5-Fluoroindole-2-carboxylic acid is a reagent for chemical synthesis. It has been used in the creation of Xa inhibitors, Fungicidal and Antitumor agents and COX-2 inhibitors. 5-Fluoroindole-2-carboxylic acid is an antagonist of NMDA receptor-associated glycine sites and raises the convulsive threshold.