4-methoxy-N-ethylamphetamine

It provides the 4‑methoxyphenethylamine backbone required for building the side chain of the drug. During synthesis, this intermediate undergoes further functional group transformations such as hydroxylation, ether formation, and substitution reactions, which convert the phenethylamine structure into the final β₂‑adrenergic agonist framework present in Formoterol. 4‑Methoxy‑N‑ethylamphetamine serves as a phenethylamine intermediate in the synthesis of Formoterol.