An improved procedure for the synthesis of branched polyethylene glycols (PEGs) with the reporter dipeptide met-βala for protein conjugation

A new and more efficient route to the synthesis of branched PEG for protein conjugation, bearing a reporter dipeptide Met-βAla, is described, which allows better purification of the final product by ion exchange chromatography. The product has the combined advantages of an ‘umbrella-like’ branched structure, which allows a better coverage of the protein surface, and the presence of the dipeptide Met-βAla which has been used to detect the position of PEGylation within the peptide sequence.