Patent ID: 7893271

Claim:
A compound of Formula I: X 1 and X 2 are independently O or S, wherein at least one of X 1 and X 2 is O; Y 1 and Y 2 are independently O or S, wherein at least one of Y 1 and Y 2 is O; R 1 is alkyl of 1-4 carbon atoms; R 2 , R 3 , and R 4 are independently hydrogen or a cation; R 5 and R 6 are independently hydrogen, halogen, alkyl of 1-8 carbon atoms, —OR 7 , —SR 8 , —CO—R 9 , —OSO 2 —Ar, or —S(O)R 10 ; R 7 is alkyl of 1-8 carbon atoms; R 8 is alkyl of 1-8 carbon atoms or aryl; R 9 is alkyl of 1-8 carbon atoms, cycloalkyl of 3-6 carbon atoms, or aryl; Ar is aryl; and R 10 is alkyl of 1-8 carbon atoms or aryl.