Phenethylamine is an alkaloid and monoamine. In the human brain, it is discussed as a putative neuromodulator or neurotransmitter. In nature phenethylamine is synthesized from the amino acid phenylalanine by enzymatic decarboxylation. It is also found in many foods, especially after microbial fermentation, e.g. in chocolate. Phenethylamine is a colorless liquid that forms a solid carbonate salt with carbon dioxide (CO₂) upon exposure to air. Phenethylamine from food (e.g. chocolate) has been discussed to have psychoactive effects. However, it is quickly metabolized by the enzyme MAO-B so that significant concentrations do not reach the brain.

Substituted phenethylamines are a broad and diverse class of compounds that include alkaloids, neurotransmitters, hormone, stimulants, hallucinogens, empathogens, anorectics, bronchodilators, and antidepressants.

The phenethylamine structure can also be found as part of more complex ring systems like in the ergoline system of LSD or the morphinan system of morphine.

Substituted phenethylamines

Substituted phenethylamines carry additional chemical modifications at the phenyl ring, the sidechain , or the amino group:

• Amphetamines are phenethylamines carrying an alpha-methyl (α-CH₃) group at the sidechain carbon atom next to the amino group.
• Catecholamines are phenethylamines carrying two hydroxy groups in positions 3 and 4 of the phenyl ring. Examples are the hormones and neurotransmitters dopamine, epinephrine (adrenaline), and norepinephrine (noradrenaline).
• The aromatic amino acids phenylalanine and tyrosine are phenethylamines carrying a carboxyl group (COOH) in alpha position.

Pharmacology

Many substituted phenethylamines are pharmacologically active drugs due to their similarity to the monoamine neurotransmitters:

• Stimulants like the plant alkaloids ephedrine and cathinone and the synthetic drugs amphetamine (speed, benzedrine) and methylphenidate.
• Hallucinogens like the plant alkaloid mescaline and the synthetic drug 2C-B.
• Empathogens like MDMA (ecstasy) and MDA.
• Anorectics like phentermine, fenfluramine, and amphetamine.
• Bronchodilators like salbutamol and ephedrine.
• Antidepressants like bupropion and the monoamine oxidase inhibitors phenelzine and tranylcypromine.

Substitution table

Some of the more important phenethylamines are tabulated below. For simplicity the stereochemistry of the sidechain is not covered in the table. Hundreds of other simple synthetic phenethylamines are known. This is due in part to the pioneering work of Alexander Shulgin, much of which is described in the book PiHKAL.

See also

• Catecholamines
• PiHKAL
• Alexander Shulgin

External links

• Book II of PiHKAL online
• Review and summary of PiHKAL, including table of 300+ phenethylamines: ascii postscript
• A Structural Tour of PiHKAL

Categorization