| abstract |
A compound of formula I ** Formula ** in which one of R1 and R2 is hydrogen, C1-C6 alkyl or a halogen, and the other is -QY, in which Q is a straight or branched C1-C10 hydrocarbon chain , saturated or unsaturated, substituted or unsubstituted, and Y is selected from the group consisting of hydroxyl, carboxyl, and amino; and R3 and R4 are independently represented from each other by -NR5R6, in which R5 and R6 are independently of each other hydrogen or substituted or unsubstituted aryl. |