Multiarmed, monofunctional, polymer for coupling to molecules and surfaces

An essentially pure monomethoxy poly(ethylene glycol) disubstituted lysine represented by the following structure:

• ##STR33## wherein mPEG.sub.a and mPEG.sub.b are monomethoxypoly (ethylene glycols) having the structure CH--(CH.sub.2 CH.sub.2 O).sub.n CH.sub.2 CH.sub.2 --, wherein n equals from 1 to about one thousand one hundred fifty (1,150), wherein n may be the same or different for mPEG.sub.a and mPEG.sub.b, and wherein said disubstituted lysine is recovered in essentially pure form by ion exchange chromatography.

A method of synthesizing a water soluble, branched polymer having a single ionizable reactive group, which ionizable reactive group is located along the polymer backbone, said method comprising the steps of:

• a) reacting two or more nonpeptidic and monofunctional polymers of the structure poly-W, wherein W is an active moiety located at the terminus of the polymer that provides the monofunctionality for the polymer, with a linger molecule having two or more active sites with which W is reactive and forming linkages therewith to create a branched polymer, wherein said linker molecule and said linkages do not comprise aromatic rings and ester groups and wherein the linker molecule further comprises a single reactive group with which active moiety --W is not reactive and that provides the single ionizable reactive group on the branched polymer backbone;
• and
• b) recovering the branched polymer in essentially pure form by ion exchange chromatography.

A method for forming monofunctional monomethoxy-poly(ethylene glycol) disubstituted lysine comprising carrying out steps to perform the following rejection:

• ##STR34## and recovering the disubstituted lysine in essentially pure form by ion exchange chromatography.

A method for forming a monofunctional monomethoxy-poly(ethylene glycol) disubstituted lysine comprising carrying out steps to perform the following reactions:

• and recovering the disubstituted lysine in essentially pure form by ion exchange chromatography.

A polymeric derivative having a structure selected from the group consisting of:

• wherein poly.sub.a and poly.sub.b are nonpeptidic and nonreactive polymeric arms that may be the same or different;
• and wherein Z comprises a moiety selected from the group consisting of moieties having a single site reactive toward nucleophilic moieties, sites that can be converted to sites reactive toward nucleophilic moieties, and the reaction product of a nucleophilic moiety and moieties having a single site reactive toward nucleophilic moieties.