Terminally-branched polymeric linkers and polymeric conjugates containing the same

A compound comprising the formula:

• E4 is selected from the group consisting of hydrogen, C1-6 alkyls, C3-12 branched alkyls, C3-8 cycloalkyls, C1-6 substituted alkyls, C3-8 substituwd cycloalkyls, aryls, substituted aryls, aralkyls, C1-6 heteroalkyls, substituted C1-6 heteroalkyls, C1-6 alkoxy, phenoxy and C1-6 heteroalkoxy;
• E1-3 are independently selected from the group consisting of hydrogen, C1-6 alkyls, C3-12 branched alkyls, C3-8 cycloalkyls. C1-6 substituted alkyls, C3-8 substituted cycloalkyls, aryls, substituted aryls, aralkyls, C1-6 heteroalkyls, substituted C1-6 heteroalkyls. C1-6 alkoxy, phenoxy, C1-6 heteroalkoxy, and at least one of E1-3 is
• wherein B is a (caving group, OH. a residue of a hydroxyl-containing moiety, a residue of an amine-containing moiety or
• wherein J1 is the same as J, or another member of the group defining J and E5 is the same as E1-4, or another member of the group defining E1-4;
• Y1-2 are independently O, S or NR9;
• M is a heteroatom selected from either X or Q;
• wherein X is an electron withdrawing group and Q is a moiety containing a free electron pair positioned three to six atoms from C(═Y2);
• R2-5 and R7-9 are independently selected from the group consisting of hydrogen, C1-6 alkyls, C3-12 branched alkyls, C3-8 cycloalkyls, C1-6 substituted alkyls, C3-8 substituted cycloalkyls, aryls, substituted aryls, aralkyls, C1-6 heteroalkyls, substituted C1-6 heteroalkyls, C1-6 alkoxy, phenoxy and C1-6 heteroalkoxy,
• (m1) and (m2) are independently zero or one;
• (n1), (n2), (p1), (p2) and (q) are independently zero or a positive integer;
• Z is an electron withdrawing group;
• and
• R1 is a polymeric residue of a substantially ron-antigenic polymer having a molecular weight of at least about 20,000 Daltons.