Patent ID: 8563651

Claim:
A method comprising; providing a poly(ethylene glycol)l having one terminal hydroxyl group; reacting the terminal hydroxyl group of the poly(ethylene glycol) with di(1-benzotriazolyl)carbonate to form a 1-benzotriazolylcarbonate ester of the poly(ethylene glycol); reacting the 1-benzotriazolylcarbonate ester of the poly(ethylene glycol) with lysine to form in one or more steps an amino acid derivative, said amino acid derivative having the following structure: wherein PEG is a poly(ethylene glycol) and Z is selected from the group consisting of H, N-succinimidyl, and 1-benzotriazolyl; and reacting the amino acid derivative with a biologically active agent under conditions to form a polymer-active agent conjugate.