5-Fluoroorotic Acid (5-FOA) is widely used in the field of yeast molecular genetics. The toxicity of 5-FOA to yeast cells with a functioning URA3 gene which encodes orotidine-5′-P decarboxylase (OMP decarboxylase), makes it especially useful for the selection and identification of mutant yeast strains. 5-FOA is most often applied with Saccharomyces cerevisiae (URA3), although it has been used in other strains including Schizosaccharomyces pombe (URA4 and URA5), Candida albicans (URA3) and the bacterium E. coli (pyrF). The use of 5-FOA in the yeast 2-hybrid system allows for the construction of activation domain hybrid libraries to identify protein-protein interactions.

5-Fluorouracil (5-FU) is a uracil analog that has a fluorine atom on the fifth carbon position. It acts as a strong anti-cancer agent where its metabolization disrupts both RNA and DNA synthesis. 5-FU metabolites, Fluorodeoxyuridine triphosphate (FdUTP) and fluorouridine triphosphate (FUTP), imitate uracil and are incorporated into RNA strands which effectively inhibits further synthesis.

Inhibition of DNA synthesis by 5-FU occurs through thymidylate synthase inhibition. A metabolite produced by 5-FU metabolism, fluorodeoxyuridine triphosphate (FdUTP), bind to the nucleotide binding site of thymidylate synthase. Halting this enzyme’s activity significantly diminishes deoxythymidine monophosphate (dTMP) production which consequently depletes dTMP within an organism.

5-Hydroxyindole is a reagent useful for a variety of preparation procedures, including: preparation of 5-vinyl-3-pyricindecarbonitrices as PKCϴ inhibitors, melanins, indole dopamine D2 receptor antagonists, anthranilic acids, anticancer agents, and tubulin inhibitors.

5-Hydroxyindole-2-carboxylic acid is used in a variety of preparation procedures, including: preparation of oxadiazole analogs as SH2 inhibitors of tyrosine kinase ZAP-70, peptidomimetic inhibitors of signal transducers and Stat3 activators, 5-hydroxyindole-2-carboxylic acid amides as histamine-3 receptor inverse agonists, melanins, and anticancer agents. Upon oxidation with KMnO4, 5-hydroxyindole-2-carboxylic acid yields pyrrole-2,3,5-tricarboxylic acid.

5-Hydroxyindole-3-acetic acid is the primary serotonin metabolite and a biomarker researched for its implication in intestinal carcinoid syndrome. Additionally, 5-HIAA has been shown to be increased in diseases such as Celiac disease and Whipple disease.

5-Methoxy-2-methylindole is a reagent useful in a variety of procedures, including: palladium acetate catalyzed arylation reactions, enantioselective Friedel-Crafts alkylations, alkylindole synthesis, and cyclopentaindolone synthesis.

5-Methoxy-DL-tryptophan is an derivative of tryptophan.