Compound with analgesic effect for use in prevention and treatment of pain

A compound of formula (II):

• wherein:
• k is 1, 2 or 3;
• X and Y are each independently NH, O or S;
• R2 and R3 are each independently OH, NH2, NO2, haloalkyl, hydroxyalkyl or alkylamino;
• and
• R4 is selected from an amino acid or a peptide,
• wherein when R4 is an amino acid, R4 is linked to the C(═O) in the structure via the backbone amino group or side chain amino group, and the carboxy group of the amino acid is optionally a methyl or ethyl ester, and
• wherein when R4 is a peptide, R4 is linked to the C(═O) in the structure via the N-terminal amino acid group of said peptide, or a side chain amino group of an amino acid in the peptide, wherein the C-terminal of the peptide is optionally modified;
• ring A is a substituted or unsubstituted aromatic heterocycle, wherein the aromatic heterocycle comprises a 5- or 6-membered heterocycle or a fused heterocycle, wherein the heteroatom(s) in the heterocycle are one or more of nitrogen, oxygen, and/or sulfur heteroatoms;
• a tautomer or stereoisomer thereof;
• and
• a pharmaceutically acceptable salt of the foregoing.