主权项 |
1. A compound of formula (A): wherein either: Y1 is Xa and Y2 is hydrogen, or Y2 is Xa and Y1 is hydrogen;
wherein Xa is selected from carboxylic acid, carboxyl ester, heterocyclyl, substituted heterocyclyl, heteroaryl and substituted heteroaryl; and R1 is selected from hydrogen, alkyl, substituted alkyl, alkenyl, substituted alkenyl, alkynyl, substituted alkynyl, cycloalkyl, substituted cycloalkyl, heterocyclyl, substituted heterocyclyl, aryl, substituted aryl, heteroaryl, substituted heteroaryl and —R15, wherein R15 comprises a linking group and a compound of formula (A); or a salt or stereoisomer thereof. |