Hydroxyphenethyl

Hydroxyphenethyl refers to a chemical moiety consisting of a phenyl ring bearing an ethyl chain, with one or more hydroxyl groups attached to the ring. The core structure is a benzene ring (C6H4) linked to an ethyl group (CH2–CH2–), with a hydroxyl substituent on the ring. The exact position of the hydroxy group on the ring yields different isomers, commonly described as ortho (2-), meta (3-), or para (4-) hydroxyphenethyl derivatives.

In practice, the term is often used to describe hydroxyphenethylamines, where the hydroxyphenethyl group carries an amino group on the side chain. When a single hydroxyl is present on the ring, it is typical to refer to hydroxyphenethyl as a general descriptor; when two ring hydroxyls are present, the term dihydroxyphenethyl or catecholphenethyl is used. Notable examples include 4-hydroxyphenethylamine (tyramine) and 3,4-dihydroxyphenethylamine (dopamine is a closely related neurotransmitter in which the ring bears two hydroxyl groups).

Biologically and pharmacologically, hydroxyphenethyl derivatives are a significant class within phenethylamines. The presence and position of ring hydroxyls influence polarity, hydrogen bonding, receptor affinity, and metabolic fate. Tyramine and dopamine illustrate how minor changes in the hydroxy pattern alter biological activity and physiological roles. The hydroxyphenethyl scaffold is also found in various natural products and serves as a versatile starting point for medicinal chemistry, including the design of receptor ligands and catechol-containing compounds. See also phenethylamine, tyramine, dopamine, and catechols.