The \(\alpha\)-amino acid which contains an aromatic side chain is

Tyrosine

The answer is (2), tyrosine.

Tyrosine is an \(\alpha\)-amino acid that contains an aromatic side chain. The side chain is a benzene ring with a hydroxyl group attached. The benzene ring gives tyrosine its aromatic properties, while the hydroxyl group makes it polar.

The other options are incorrect. Proline does not contain an aromatic side chain. Valine and tryptophan do contain aromatic side chains, but they are \(\beta\)-amino acids, not \(\alpha\)-amino acids.