Oligomer conjugates of heteropentacyclic nucleosides

1. A compound having the following structure:

wherein:

R 2 is hydrogen or hydroxyl;

R 3 is hydroxyl when R 2 is hydrogen and R 3 is hydrogen when R 2 is hydroxyl;

(a) is two;

X is an amide linkage; and

each POLY is independently a water-soluble, non-peptidic oligomer,

and 5′-phosphates and 3′,5′-cyclic phosphates thereof and ammonium and alkali metal salts of each of the 5′-phosphates and 3′,5′-cyclic phosphates.

2. The compound of claim 1 , wherein the weight average molecular weight of each water-soluble, non-peptidic oligomer is less than 400 Daltons.

3. The compound of claim 1 , wherein each water-soluble, non-peptidic oligomer is a poly(alkylene oxide).

4. The compound of claim 3 , wherein each poly(alkylene oxide) is a poly(ethylene oxide).

5. The compound of claim 4 , wherein the water-soluble, non-peptidic oligomer has a number of repeating monomers in the range of from 1 to 30.

6. The compound of claim 5 , wherein the water-soluble, non-peptidic oligomer has a number of repeating monomers in the range of from 1 to 10.

7. The compound of claim 3 , wherein the poly(alkylene oxide) includes an alkoxy or hydroxy end-capping moiety.

8. A composition comprising (i) a compound of claim 1 , and (ii) a pharmaceutically acceptable excipient.

9. A composition of matter comprising a compound of claim 1 present in a dosage form.

10. The compound of claim 1 , wherein the compound is selected from a compound of the formula

wherein for each occurrence, n is an integer from 1 to 15.

11. The compound of claim 10 , wherein for each occurrence, n is an integer from 1 to 10.

12. The compound of claim 11 , wherein for each occurrence, n is 5.

13. A composition comprising (i) a compound of claim 10 , and (ii) a pharmaceutically acceptable excipient.