Patent ID: 7122573

Claim:
A compound having the structural formula (I) wherein: R 1 , R 2 and R 3 are independently selected from the group consisting of hydroxyl, halo, sulfhydryl, alkoxy, aryloxy, and aralkyloxy; R 4 is O; R 5 is selected from the group consisting of SH, acyloxy, and N(R x ) 2 wherein the R x may be the same or different and are hydrogen or alkyl; R 6 and R 8 are independently selected from the group consisting of alkyl, alkoxy, aryloxy, and aralkyloxy; R 7 and R 9 are independently selected from the group consisting of hydrogen, alkyl, alkoxy, aryloxy, and aralkyloxy; and R 10 and R 11 are independently selected from the group consisting of hydrogen, hydroxyl, alkyl, alkoxy, and halo, with the proviso that when (a) R 7 , R 9 , R 10 , and R 11 are hydrogen, (b) R 1 , R 2 , R 3 , R 6 , and R 8 are hydroxyl, and (c) R 4 is O, then (d) R 5 is other than 3,4,5-trihydroxybenzoyloxy or 3,4,5-trimethoxybenzoyloxy.