Methods of synthesizing insulin polypeptide-oligomer conjugates, and proinsulin polypeptide-oligomer conjugates and methods of synthesizing same

A process for synthesizing a monoconjugate insulin-oligomer comprising: (i) contacting a proinsulin with an oligomer, wherein the proinsulin comprises an insulin having an A chain and a B chain, and a coupled C-peptide connector a first end with the C-terminus of the B-chain and coupled at a second end to the N terminal of the a chain by peptide bonds, and a peptide coupled to the N terminal of the B chain leader by a peptide bond, in which peptide bonds are capable of being cleaved enzymatically to produce the mono-conjugated insulin-oligomer, and wherein the oligomer comprises a hydrophilic moiety and a lipophilic moiety, and wherein the proinsulin and the oligomer are contacted under conditions sufficient to couple the oligomer to lysine residue of the insulin portion of the proinsulin and provide a proinsulin-oligomer monoconjugate; and (ii) enzymatically cleaving the C-peptide and the leader peptide oligomer monoconjugate-proinsulin to provide the insulin-oligomer monoconjugate.