1. A compound of the formula:

wherein:

X1 is hydrogen, halogen, hydroxy, amino, cyano, nitro, or oxo, or alkyl(C?12), alkenyl(C?12), alkynyl(C?12), aryl(C?18), aralkyl(C?18), heterocycloalkyl(C?12), heteroaryl(C?12), acyl(C?12), C(O)-alkoxy(C?12), alkoxy(C?12), alkenyloxy(C?12), alkynyloxy(C?12), aryloxy(C?18), aralkyloxy(C?18), heterocycloalkyloxy(C?12), heteroaryloxy(C?12), acyloxy(C?12), alkylamino(C?12), dialkylamino(C?12), alkenylamino(C?12), alkynylamino(C?12), arylamino(C?18), aralkylamino(C?18), heterocycloalkylamino(C?12), heteroarylamino(C?12), amido(C?12), -arenediyl(C?6)-heteroaryl(C?12), or a substituted version of any of these groups, or is taken together with X6 as defined below;

X2 and X5 are each independently hydrogen, hydroxy, nitro, cyano, or amino, or

alkyl(C?12), alkenyl(C?12), alkynyl(C?12), aryl(C?18), aralkyl(C?18), heterocycloalkyl(C?12), heteroaryl(C?12), acyl(C?12), alkoxy(C?12), alkenyloxy(C?12), alkynyloxy(C?12), aryloxy(C?18), aralkyloxy(C?18), heterocycloalkyloxy(C?12), heteroaryloxy(C?12), acyloxy(C?12), alkylthio(C?12), alkenylthio(C?12), alkynylthio(C?12), arylthio(C?18), aralkylthio(C?18), heterocycloalkylthio(C?12), heteroarylthio(C?12), acylthio(C?12), alkylamino(C?12), dialkylamino(C?12), alkenylamino(C?12), alkynylamino(C?12), arylamino(C?18), aralkylamino(C?18), heterocycloalkylamino(C?12), heteroarylamino(C?12), amido(C?12), -alkanediyl(C?6)-heterocycloalkyl(C?12), or a substituted version of any of these groups; or

wherein:

R is hydrogen; or

alkyl(C?12), alkenyl(C?12), acyl(C?12), aryl(C?12), aralkyl(C?12), or a substituted version of any of these groups;

X3 and X4 are each independently hydrogen, hydroxy, or amino, or

alkoxy(C?12), alkenyloxy(C?12), alkynyloxy(C?12), aryloxy(C?18), aralkyloxy(C?18), heterocycloalkyloxy(C?12), heteroaryloxy(C?12), acyloxy(C?12), alkylamino(C?12), dialkylamino(C?12), alkenylamino(C?12), alkynylamino(C?12), arylamino(C?18), aralkylamino(C?18), heterocycloalkylamino(C?12), heteroarylamino(C?12), amido(C?12), -alkanediyl(C?6)-heterocycloalkyl(C?12), or a substituted version of any of these groups; or

wherein:

R is hydrogen; or

alkyl(C?12), alkenyl(C?12), acyl(C?12), aryl(C?12), aralkyl(C?12), or a substituted version of any of these groups;

X6 is hydrogen, halogen, hydroxy, amino, nitro, or cyano, or

alkyl(C?12), alkenyl(C?12), alkynyl(C?12), aryl(C?18), aralkyl(C?18), heterocycloalkyl(C?12), heteroaryl(C?12), acyl(C?12), alkoxy(C?12), alkenyloxy(C?12), alkynyloxy(C?12), aryloxy(C?18), aralkyloxy(C?18), heterocycloalkyloxy(C?12), heteroaryloxy(C?12), acyloxy(C?12), alkylamino(C?12), dialkylamino(C?12), alkenylamino(C?12), alkynylamino(C?12), arylamino(C?18), aralkylamino(C?18), heterocycloalkylamino(C?12), heteroarylamino(C?12), or amido(C?12), or a substituted version of any of these groups, or is taken together with X1 as defined below;

Y1, Y2, Y3, Y4, and Y5 are each independently hydrogen, amino, cyano, halo, hydroxy, or nitro, or

alkyl(C?12), alkenyl(C?12), alkynyl(C?12), aryl(C?12), aralkyl(C?12), heteroaryl(C?12), heterocycloalkyl(C?12), acyl(C?12), or a substituted version of any of these groups;

X1 and X6 when taken together have the formula:

wherein:

X1? and X6? are each independently hydrogen, hydroxy, halo, or amino;

alkyl(C?12), alkenyl(C?12), alkynyl(C?12), aryl(C?12), aralkyl(C?12), heteroaryl(C?12), acyl(C?12), or a substituted version of any of these groups;

provided that at least one of Y1, Y2, Y3, Y4, or Y5 are hydroxy or alkoxy(C?12) and that X2, X3, X4, and X5 are not all hydrogen, or that when X1 is oxo then X6 is not aryl(C?8);

or a pharmaceutically acceptable salt thereof.