Phenylalanine derivatives of formula (1) are described:
wherein
L
1
is a linker atom or group;
X
1
is a group selected from —N(R
3
)CO—, —N(R
3
)SO
2
—, —N(R
3
)C(O)O— or
—N(R
3
)CON(R
3a
)—; and
R is a carboxylic acid or a derivative thereof.
The compounds are able to inhibit the binding of a 4 integrins to their ligands and are of use in the prophylaxis and treatment of diseases or disorders involving inflammation.