Patent ID: 7420000

Claim:
A compound of general formula: wherein: R 2 is hydrogen, alkyl, allyl, aryl, acyl, sulfonyl, amino, alkylamino, dialkylamino, acylamino, sulfonylamino, or alkoxy; R 3 is hydrogen, alkyl, alkenyl, aryl, phosphonic acid, phosphonate or phosphonamido; R 4 is alkyl, aryl, furyl, thienyl, pyrrolyl, benzofuryl, benzothienyl, allyl, alkenyl, alkynyl, or allenyl; R 5 is hydrogen, alkyl, or aryl; R 6 is hydrogen, alkyl, hydroxyalkyl, polyhydroxyalkyl, aryl, pyridyl, alkenyl, alkynyl, allenyl, formyl, acyl, aminoacyl, carboxy or alkoxyacyl; R a and R b are independently hydrogen, alkyl, aryl, ammonium, tetraalkyl ammonium or a metal cation, wherein at least: R 3 is aryl; or R 4 is furyl, thienyl, pyrrolyl, benzofuryl, or benzothienyl; or R 6 is hydroxyalkyl, polyhydroxyalkyl, or 2-pyridyl.