Improved preparation of an amino acid type poly(ethylene glycol) derivative.

An amino acid type poly(ethylene glycol) is a useful tool for preparation of a bi- or multivalent poly(ethylene glycol) hybrid of bioactive peptides, but synthesis is problematic. The amino acid type poly(ethylene glycol) was prepared from poly(oxyethylene)diglycolic acid followed by introduction of a fluorenylmethyloxycarbonyl group. The resulting product could be purified easily by LH-20 column chromatography and HPLC.