Conjugation reactions

A process for forming a biologically active conjugate compound, comprising a conjugation step in which a biologically active starting material of the general formula I

• is reacted in an amide bond forming step with a reagent of the general formula II
• to form an amide-linked conjugate, the process increasing the stability of the biologically active starting material,
• in which R is a biologically active moiety;
• L1 is a bond or a divalent organic linker;
• and
• X1 is —NHR6 or —COR7, in which R6 is selected from the group consisting of hydrogen, C1-6 alkyl, aryl and amine activating group and R7 is hydroxyl or a carboxyl activating group;
• X2 is selected from the group consisting of a polymer formed from ethylenically unsaturated monomers and joined through a terminal group;
• R1 and R2 are each independently selected from the group consisting of H, halogen, C1-C20 alkyl, C3-C8 cycloalkyl, C(═O)R15, C(═O)NR16R17, COCl, OH, CN, C2-C20 alkenyl, oxiranyl, glycidyl, aryl, heterocyclyl, aralkyl and aralkenyl, in any of which the alkyl, alkenyl or aryl, heterocyclyl or cycloalkyl groups there may be from 1 to 3 substituents selected from the group consisting of hydrogen, hydroxy C1-C4 alkoxy, acyloxy, aryl, heterocyclyl, C(═O)R15, C(═O)NR16R17, oxyranyl and glycidyl;
• R15 is selected from the group consisting of alkyl of from 1 to 20 carbon atoms, alkoxy of from 1 to 20 carbon atoms, oligo(alkoxy) in which each alkoxy group has 1 to 3 carbon atoms, aryloxy and heterocyclyloxy, any of which groups may have substituents selected from the group consisting of optionally substituted alkoxy, oligoalkoxy, amino and hydroxyl groups;
• R16 and R17 are independently selected from the group consisting of H and alkyl of from 1 to 20 carbon atoms which alkyl groups, may have substituents selected from the group consisting of alkoxy, acyl, acyloxy, alkoxycarbonyl, alkenoxycarbonyl, aryl and hydroxy, or R16 and R17 may be joined together to form an alkanediyl group of from 2 to 5 carbon atoms, thus forming a 3- to 6-membered ring;
• R3 and R4 are independently selected from the group consisting of hydrogen, and C1-6 alkyl, or R3 and R4 together are ═O or ═NR8 where R8 is hydrogen or C1-4 alkyl;
• R5 is selected from the group consisting of a bond, —O—, —S— and divalent organic groups;
• L2 is a bond or a divalent linker and,
• where X1 is NHR6, X3 is COR7 and
• where X1 is COR7, X3 is NHR6 and
• r is an integer of at least 1, and
• wherein X2 is a polymer chain consisting essentially of a homopolymer formed from 2-methacryl oyloxyethyl-2′-trimethylammoniumethyl phosphate inner salt, and the compound of formula I is a protein, and
• wherein the compound of formula II is made in a preliminary polymerisation step in which ethylenically unsaturated monomers are polymerised in the presence of an initiator of the general formula XI
• in which X3, L2 and R1 to R5 are as defined above and X4 is selected from the group consisting of Cl, Br, I, OR51, SR52, SeR52, OP(═O)R52, OP(═O)(OR52)2, O—N(R52)2 and S—C(═S)N(R52)2, where R51 is alkyl of from 1 to 20 carbon atoms in which each of the hydrogen atoms may be independently replaced by halide, R52 is aryl or a straight or branched C1-C20 alkyl group, and where an N(R52)2 group is present, the two R52 groups may be joined to form a 5- or 6-membered heterocyclic ring.