Patent ID: 8633277

Claim:
A method of preparing a conjugate comprising the step of contacting a polymeric reagent with an active agent under suitable conjugation conditions to thereby provide the conjugate, wherein the polymeric reagent has the following structure wherein: POLY 1 is a water-soluble polymer selected from the group consisting of poly(alkylene oxide), poly(vinyl pyrrolidone), poly(vinyl alcohol), polyoxazoline and poly(N-acryloylmorpholine); POLY 2 is a water-soluble polymer selected from the group consisting of poly(alkylene oxide), poly(vinyl pyrrolidone), poly(vinyl alcohol), polyoxazoline and poly(N-acryloylmorpholine); (a) is 0, 1, 2 or 3; (b) is 0, 1, 2 or 3; (e) is 0, 1, 2 or 3; (f′) is 0, 1, 2 or 3; (g′) is 0, 1, 2 or 3; (h) is 0, 1, 2 or 3; (j) is 0 to 20; each R 1 is independently H or an organic radical selected from the group consisting of alkyl, substituted alkyl, alkenyl, substituted alkenyl, alkynyl, substituted alkynyl, aryl and substituted aryl; X 1 , when present, is a first spacer moiety; X 2 , when present, is a second spacer moiety; X 5 , when present, is a fifth spacer moiety; X 6 , when present, is a sixth spacer moiety; X 7 , when present, is a seventh spacer moiety; X 8 , when present, is an eighth spacer moiety; R 5 is a branching moiety selected from the group consisting of wherein (p) is 1-10 and (q) is 1-10; and Z is a reactive group suitable for reaction with an electrophile or nucleophile of the active agent.