4'-Demethylepipodophyllotoxin is an inhibitor of microtubule assembly.

4,6-Benzylidene-4-nitrophenyl-alpha-D-maltoheptaoside is a reagent used for chemical synthesis.

4,6-Dihydroxy-2-methylpyrimidine is a reagent used in chemical synthesis.

4-(Benzyloxy)aniline is used as a building block for biochemical synthesis.

4-Acetoxyindole is an indole with an acetyl group. It is used as a starting reactant in the preparation of 4-oxoquinoline, which is used as an anti-HIV agent. In chromatography it is used to help optimize peak capacity for the separation of low molecular weight molecules during gradient elution.

P-aminophenyl phosphate (pAPP) can be used as a substrate for alkaline phosphatase enzymatic reactions in order to electrochemically quantify ALP activity.

The enzymatic reaction results in the production of phenol, which can be quantified and used to analyze ALP concentrations.

ALP is a naturally occurring enzyme and can be found in human tissue in the liver, bone and intestines. Usual concentrations of ALP range between 25-100 IU/L. A significant spike outside of that range could act as a signal for many diseases.

4-Aminophenyl-β-D-galactopyranoside is a substrate for β-galactosidase. It is also a weak β-D-galactosidase inducer and can be used in affinity chromatography for isolation of galactose-binding. The 4-aminophenyl releases upon cleavage by β-galactosidase. It can then be assayed by electro-oxidation to 4-imino quinone while recording changes in the potential or current galvanic system.

4-Azaindole is used a reagent for the creation of complex molecules. When combined with a bisalkoxyalkyl spacer, they can be used to target melatonin MT 1 receptors over MT 2 receptors.

4-Benzyloxyindole is a reactant in a variety of preparation procedures. It is used in the synthesis of 4-aryl-4H-chromenes as an inducer of apoptosis, in the synthesis of indol-3-yl tetramethylcyclopropyl ketones as a CB2 cannabinoid receptor ligand, and in the synthesis of hepatitis C inhibitors. Additionally, 4-Benzyloxyindole is used to prepare carbon-11-labeled-4-aryl-4H-chromenes as PET agents in cancer studies, to prepare indoles through Bartoli reductive cyclization, and to synthesize oxopyrrolidine analogs in iodine-catalyzed Markovnikov additions.

4-Benzyloxyindole-2-carboxylic acid ethyl ester is a reagent for building organic molecules.

4-Bromoindole is studied for its potential use as a GSK-3 inhibitor.

Substrate for horseradish peroxidase (HRP). HRP catalyzes oxidation of 4-chloro-1-naphthol in the presence of peroxide to the blue, insoluble product 4-chloro-1-naphthon. It is used for both blotting and immunohistochemical staining, but is less sensitive than other precipitating HRP substrates.