4-(2-Aminopropyl)indole

4-(2-Aminopropyl)indole (4-API), also known in the past as α-methylisotryptamine (α-Me-isoT), is a serotonin receptor modulator of the phenethylamine and amphetamine families.^[1][2][3][4] It is one of seven possible positional isomers of (2-aminopropyl)indole (API), with other examples including α-methyltryptamine (AMT; 3-API) and α-methylisotryptamine (isoAMT; 1-API).^[2][3][4] The drug is a sort of hybrid structure between phenethylamines and tryptamines.^[1][2][3][4]

Other names4-API; 4-IT; α-Methylisotryptamine; α-Me-isotryptamine; α-Me-isoT

Drug classSerotonin receptor modulator; Serotonin 5-HT₂ receptor modulator; Monoamine oxidase inhibitor

ATC code

• None

CAS Number

• 21005-59-4

Quick facts Clinical data, Other names ...

4-(2-Aminopropyl)indole

Clinical data
Other names	4-API; 4-IT; α-Methylisotryptamine; α-Me-isotryptamine; α-Me-isoT
Drug class	Serotonin receptor modulator; Serotonin 5-HT2 receptor modulator; Monoamine oxidase inhibitor
ATC code	None
Identifiers
IUPAC name 1-(1H-indol-4-yl)propan-2-amine
CAS Number	21005-59-4
PubChem CID	55254455
ChemSpider	26495445
Chemical and physical data
Formula	C11H14N2
Molar mass	174.247 g·mol−1
3D model (JSmol)	Interactive image
SMILES CC(CC1=C2C=CNC2=CC=C1)N
InChI InChI=1S/C11H14N2/c1-8(12)7-9-3-2-4-11-10(9)5-6-13-11/h2-6,8,13H,7,12H2,1H3 Key:FSNFARLFBCWJMF-UHFFFAOYSA-N

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It shows affinity for the serotonin 5-HT₂ receptor (K_i = 5,000 nM), with its affinity being only 2-fold lower than that of AMT (K_i = 2,500 nM) in the same study.^[3] The drug reverses the facilitation of pentylenetetrazol-induced seizures evoked by the monoamine depleting agent reserpine in rodents, albeit with much lower potency than AMT (10-fold) and certain other API positional isomers.^[2] It showed activity as a monoamine oxidase inhibitor (MAOI) in vitro, with slightly higher potency than AMT.^[2]

The synthesis and identification of 4-API have been described.^[3][4]

4-API was first described in the literature in a patent as a potential antiasthmatic agent by Albert Hofmann and Franz Troxler at Sandoz in 1963.^[1][5] Subsequently, it was studied by Aurelio Cerletti and colleagues in 1968^[2] and by Richard Glennon and colleagues in 1988.^[3] The drug was referred to as "α-methyl-isotryptamine" or "α-Me-isoT" by Glennon and colleagues, but this term subsequently came to be used to refer to 1-API instead.^[3] Certain APIs, such as AMT and 5-(2-aminopropyl)indole (5-API), have been encountered as novel designer drugs, but 4-API does not appear to have been encountered as of 2014.^[4]