主权项 |
1. A compound, which comprises: wherein A is N, S, or O; R is independently a hydrogen, amino, alkylamino, dialkylamino, hydroxy, or alkoxy radical; and, X and Y are independently a hydrogen, amino, alkylamino, dialkylamino, alkylacylamino, hydroxy, alkoxy, alkyl, alkenyl, or arylacylamino radical optionally substituted by 1-3 radicals of alkyl, alkenyl, amino, alkylamino, hydroxy, alkoxy, aryl or heteroaryl. |