Functionalized polymers

1. A conjugate, or a pharmaceutically acceptable salt thereof, comprising a water-soluble, non-peptidic, and non-nucleotidic polymer backbone having at least one terminus covalently bonded to a structure of formula (1):

or a salt thereof,

wherein:

A is the point of covalent bonding to the terminus of the polymer backbone, wherein the polymer backbone is poly(ethylene glycol);

E is O;

K is selected from the group consisting of: alkylene, alkyleneoxyalkylene, and oligomeric alkyleneoxyalkylene;

G is selected from the group consisting of: hydrogen, alkoxy, and a hydrophobic separation handle;

Z 1 is O;

Z 2 is O;

L is selected from the group consisting of: a divalent radical of a nucleoside, alkylene, alkyleneoxyalkylene, oligomeric alkyleneoxyalkylene, and unsubstituted and substituted arylene;

R 1 is absent or a hydrophobic separation handle;

M is a biologically active molecule; and

R is absent.

2. The conjugate of claim 1 , wherein the poly(ethylene glycol) has an average molecular weight from about 500 Da to about 100,000 Da.

3. The conjugate of claim 1 , wherein K is selected from the group consisting of: methylene, ethylene, propylene, isopropylene, butylene, isobutylene, sec-butylene, tert-butylene, and hexylene, or a residue from diethylene glycol, triethylene glycol, tetraethylene glycol or hexaethylene glycol.

4. The conjugate of claim 1 , wherein G is a substituted or unsubstituted trityloxy.

5. The conjugate of claim 1 , wherein L is a substituted or unsubstituted C 1 -C 12 alkylene.

6. The conjugate of claim 1 , wherein said biologically active molecule is selected from the group consisting of enzymes, peptides, polypeptides, nucleotides, oligonucleotides, polynucleotides, and therapeutic agents having a molecular weight of less than 1000 g/mol.

7. A conjugate, or a pharmaceutically acceptable salt thereof, comprising a compound of formula (2):

or a salt form thereof,

wherein:

polymer is a linear poly(ethylene glycol), wherein each linking group is bonded at a different terminus of said poly(ethylene glycol);

E is O;

E 1 is O or S;

K and K 1 are independently selected from the group consisting of: alkylene, alkyleneoxyalkylene, and oligomeric alkyleneoxyalkylene;

G and G 1 are independently absent or are selected from the group consisting of: alkoxy and a hydrophobic separation handle;

Z 1 is O;

Z 2 is O;

Z 3 and Z 4 are independently selected from 0 and NH, wherein no more than one of Z 3 and Z 4 is NH;

L is a divalent radical of an alkylene;

L 1 is selected from the group consisting of: a divalent radical of a nucleoside, alkylene, alkyleneoxyalkylene, oligomeric alkyleneoxyalkylene, and unsubstituted and substituted arylene;

R and R 1 are absent;

M is a biologically active molecule; and

M 1 is a biologically active molecule.

8. The conjugate of claim 7 , wherein the poly(ethylene glycol) has an average molecular weight from about 500 Da to about 100,000 Da.

9. The conjugate of claim 7 , wherein K or K 1 is independently selected from the group consisting of: methylene, ethylene, propylene, isopropylene, butylene, isobutylene, sec-butylene, tert-butylene, and hexylene, or a residue from diethylene glycol, triethylene glycol, tetraethylene glycol or hexaethylene glycol.

10. The conjugate of claim 7 , wherein G or G 1 is independently a substituted or unsubstituted trityloxy.

11. The conjugate of claim 7 , wherein L or L 1 is independently a substituted or unsubstituted C 1 -C 12 alkylene.

12. The conjugate of claim 1 , wherein said biologically active molecule is selected from the group consisting of enzymes, peptides, polypeptides, nucleotides, oligonucleotides, polynucleotides, and therapeutic agents having a molecular weight of less than 1000 g/mol.

13. A conjugate, or a pharmaceutically acceptable salt thereof, comprising a compound of formula (3):

or a salt form thereof,

wherein:

polymer is a linear poly(ethylene glycol), wherein M 2 and the phosphonate-derived functional group are bonded at a different terminus of said poly(ethylene glycol);

E is O;

E 1 is O or S;

K is selected from the group consisting of: alkylene, alkyleneoxyalkylene, and oligomeric alkyleneoxyalkylene;

G is selected from the group consisting of: hydrogen, alkoxy, and a hydrophobic separation handle;

Z 1 is O;

Z 2 is O;

L is selected from the group consisting of: a divalent radical of nucleoside, alkylene, alkyleneoxyalkylene, oligomeric alkyleneoxyalkylene, and unsubstituted and substituted arylene;

M is a biologically active molecule;

M 2 is selected from O, S or NH; and

R is absent; and

R 2 is hydrogen or a protecting group.

14. The conjugate of claim 13 , wherein the poly(ethylene glycol) has an average molecular weight from about 500 Da to about 100,000 Da.

15. The conjugate of claim 13 , wherein K is selected from the group consisting of: methylene, ethylene, propylene, isopropylene, butylene, isobutylene, sec-butylene, tert-butylene, and hexylene, or a residue from diethylene glycol, triethylene glycol, tetraethylene glycol or hexaethylene glycol.

16. The conjugate of claim 13 , wherein G is a substituted or unsubstituted trityloxy.

17. The conjugate of claim 16 , wherein G is selected from a monoalkoxy substituted trityloxy group or dialkoxy substituted trityloxy group.

18. The conjugate of claim 13 , wherein L is a substituted or unsubstituted C 1 -C 12 alkylene.

19. The conjugate of claim 13 , wherein R 2 is selected from the group consisting of trityl, monoalkoxytrityl, dialkoxytrityl, pixyl, alkoxypixyl, fluorenylmethyloxycarbonyl, alkylcarboxyl, benzoyl, tetrahydropyranyl, methyl.

20. The conjugate of claim 13 , wherein said biologically active molecule is selected from the group consisting of enzymes, peptides, polypeptides, nucleotides, oligonucleotides, polynucleotides, and therapeutic agents having a molecular weight of less than 1000 g/mol.