Composition comprising a polymeric reagent

1. A method for preparing a polymeric reagent, the method comprising:

(i) reducing the nitro group of 7-nitro-4-fluorenecarboxylic acid (I),

by reaction of (I) with a reducing agent to thereby form 4-carboxylic acid-7-amino fluorene (II),

(ii) converting (II) into 9-hydroxymethyl-4-carboxylic acid-7-(amidoglutaric acid)fluorene,

by either:

(ii-a) protecting the amino group of 4-carboxylic acid-7-amino fluorene (II) to thereby form 4-carboxylic acid-N-protected-7-amino fluorene (III),

(ii-b) reacting (III) with a formylating agent to thereby form 9-formyl-4-carboxylic acid-N-protected-7-amino fluorene (IV),

(ii-c) reducing the formyl group of (IV) to form 9-hydroxymethyl-4-carboxylic acid-N-protected-7-amino fluorene (V),

(ii-d) removing the N-protecting group from (V) to form 9-hydroxymethyl-4-carboxylic acid-7-amino fluorene (VI),

(ii-e) reacting (VI) with glutaric anhydride to form 9-hydroxymethyl-4-carboxylic acid-7-(amidoglutaric acid)fluorene (VII),

or

(ii-a′) reacting (II) with glutaric anhydride to form 4-carboxylic acid-7-(amidoglutaric acid)fluorene (IX),

(ii-b′) reacting (IX) with a formylating agent to form 9-formyl-4-carboxylic acid-7-(amidoglutaric acid)fluorene (X),

(ii-c′) reducing the formyl group of (X) to form 9-hydroxymethyl-4-carboxylic acid-7-(amidoglutaric acid)fluorene (VII),

(iii) reacting (VII) with methoxypoly(ethylene glycol)amine, mPEG-NH 2 , under conditions effective to form 9-hydroxymethyl-4-methoxypoly(ethylene glycol)carboxamide)-7-(methoxypoly(ethylene glycol)-glutaramide)fluorene (VIII),

and

(iv) converting the 9-hydroxymethyl group of (VIII) into an active carbonate ester, (XI).

2. The method of claim 1 , wherein step (ii) comprises steps (ii-a) through (ii-e).

3. The method of claim 1 , wherein step (ii) comprises steps (ii-a′) through (ii-c′).

4. The method of claim 1 , where in step (i), the nitro group of 7-nitro-4-fluorenecarboxylic acid is reduced by hydrogenation over a palladium/carbon catalyst.

5. The method of claim 2 , wherein the protecting group in 4-carboxylic acid-N-protected-7-amino fluorene (III) is a BOC (tert-butyloxycarbonyl) protecting group.

6. The method of claim 1 , wherein the formylating agent in step (ii-b) or in step (ii-b′) is ethyl formate.

7. The method of claim 1 , where in step (iii), mPEG-NH 2 is reacted with (VII) in the presence of a condensing agent and a base.

8. The method of claim 7 , wherein the condensing agent is 1,3-dicyclohexylcarbodiimide (DCC) or diisopropylcarbodiimide.

9. The method of claim 8 , wherein the condensing agent is 1,3-dicyclohexylcarbodiimide (DCC) and the base is N-hydroxybenzotriazole (HOBT).

10. The method of claim 1 , wherein the mPEG-NH 2 in step (iii) has a weight average molecular weight in a range selected from the group consisting of from about 120 daltons to about 6,000 daltons, from about 6,000 daltons to about 100,000 daltons, and from about 10,000 daltons to about 85,000 daltons.

11. The method of claim 1 , wherein the mPEG-NH 2 in step (iii) has a weight average molecular weight selected from the group consisting of about 10,000 daltons, about 20,000 daltons and about 30,000 daltons.

12. The method of claim 1 , wherein the active carbonate ester of step (viii) is an N-succinidmidyl carbonate ester or a benzotriazolyl carbonate ester.

13. The method of claim 12 , wherein step (viii) comprises reacting (VIII) with triphosgene and adding N-hydroxysuccinimide to thereby form the active carbonate ester (XI) having a structure,

14. The method of claim 1 , further comprising the steps of:

(ix) isolating and purifying the active carbonate ester in (XI).