Patent ID: 7939627

Claim:
A compound of formula (1): wherein X is a tyrosine residue or a methionine residue; each of Y and Z is independently selected from the group consisting of a single bond and a divalent peptide group consisting of 1-10 amino acid residues, R 1 is hydrogen or alkyl, R 2 is hydroxyl, amino, alkylamino or dialkylamino, R 3 is hydrogen, alkyl, amino, alkylamino, dialkylamino or substituted or unsubstituted alkylcarbonylamino, R 4 is hydrogen, alkyl, carboxy, carbamoyl, alkylcarbamoyl, dialkylcarbamoyl or a group of formula (2): wherein W is an amino acid residue, m is 1 or 2, and n is an integer of 0-2, with the proviso that when n is 0, R 3 is hydrogen or alkyl, or a pharmaceutically acceptable salt thereof.