Patent ID: 7101864

Claim:
A compound of formula I: wherein R 1 and R 2 are the same and are selected from hydrogen, an alkali metal cation or an optionally substituted ammonium cation; R 3 is —NHR 4 , where R 4 is selected from the group consisting of alkoxyalkyl, hydroxyalkyl, alkoxy, carboxyalkyl, alkoxycarbonylalkyl, aryloxycarbonylalkyl, acyloxy-alkoxycarbonylalkyl, C 1 –C 10 aminoalkyl, C 3 –C 10 aminocycloalkyl, guanidinoalkyl, guanidinocycloalkyl, amidinoalkyl, or amidinocycloalkyl, or R 3 is an amide of an amino acid or an amide of an oligopeptide, and X is O, or a pharmaceutically acceptable salt thereof.