A

1. A compound of the Formula I or Formula II:

wherein:

R 1 and R 2 are independently chosen from hydrogen or loweralkyl;

R 3 hydrogen,;

X is five or six membered monocyclic arylene or heteroarylene that is attached to the purine ring at a carbon atom;

Y is a covalent bond or alkylene in which one carbon atom can be optionally replaced by —O—, —S—, or —NH—; and

Z is optionally substituted monocyclic aryl or optionally substituted monocyclic heteroaryl.

2. The compound of claim 1 , wherein,

X is phenylene or pyrazolene,

Y is lower alkylene in which one carbon atom can be optionally replaced by —O—, —S—, or —NH—, and

Z is optionally substituted phenyl, optionally substituted oxadiazolyl, optionally substituted isoxazolyl, or optionally substituted pyridyl.

3. The compound of claim 2 , wherein R 1 is lower alkyl and R 2 is hydrogen.

4. The compound of claim 2 , wherein X is optionally substituted 1,4-pyrazolene.

5. The compound of claim 2 , wherein Z is optionally substituted phenyl.

6. The compound of claim 2 , wherein Z is optionally substituted oxadiazolyl.

7. The compound of claim 2 , wherein Z is optionally substituted pyridyl.

8. The compound of claim 2 , wherein Z is optionally substituted isoxazolyl.

9. The compound of claim 2 , wherein R 1 is hydrogen and R 2 is lower alkyl.

10. The compound of claim 2 , wherein R 1 and R 2 are independently lower alkyl.

11. The compound of claim 2 , wherein X is phenylene.

12. The compound of claim 2 , wherein Y is methylene.

13. The compound of claim 2 , wherein Y is —O—CH 2 —.

14. The compound of claim 1 , wherein Y is a covalent bond.

15. A pharmaceutical composition comprising a therapeuticially effective amount of a compound of claim 1 and a pharmaceutically acceptable carrier.