Protein conjugates and methods for their preparation

A conjugated peptide according to formula (I)

• wherein
• Prot is a peptide-derived radical, wherein said peptide-derived radical formed by the formal removal of a hydrogen atom from an amino group (—NH2) of said peptide,
• R1 is arylene or a heteroarylene, optionally substituted with a C1-6-alkyl, halogen, cyano, nitro, hydroxyl, carboxyl, or aryl group;
• R2 is a linker comprising the diradical C(═O)—NH—, and
• R3 is a property-modifying group;
• R4 is hydrogen or C1-6-alkyl;
• R5 is —CH2— or —C(═O)—,
• or pharmaceutically acceptable salts, thereof.