Patent ID: 7345081

Claim:
A compound of formula I: wherein X 1 and X 2 are independently O or S; L is a bond, —C(X 3 )—, —C(X 3 )NR 12 or —C(X 3 )O— wherein X 3 is O or S and R 12 is H or R 1 ; R 1 is alkyl, a carbocycle, carbocycle-substituted alkyl, a heterocycle or heterocycle-substituted alkyl, wherein each is optionally substituted with halogen, hydroxyl, mercapto, carboxyl, alkyl, haloalkyl, alkoxy, alkylsulfonyl, amino, nitro, aryl and heteroaryl; R 2 is alkyl, cycloalkyl, cycloalkylalkyl, aryl, aralkyl, a heterocycle or heterocyclylalkyl; R 3 is H or alkyl; R 4 and R 4 ′ are independently H, alkyl, aryl, aralkyl, cycloalkyl, cycloalkylalkyl, heteroaryl, or heteroaralkyl wherein each is optionally substituted with halogen, hydroxyl, mercapto, carboxyl, alkyl, alkoxy, amino and nitro; R 5 , and R 5′ are each independently H or alkyl; R 6 is H or alkyl; and salts and solvates thereof.