X is selected from the group consisting of O and S;

R³ is selected from the group consisting of cyano, nitro, —C(Z)R⁸, —S(O₂)NR⁹R¹⁰, —S(O₂)R¹¹, and optionally substituted lower alkyl;

R¹, R², R⁴, R⁵, R⁷, R⁹ and R¹⁰ are independently selected from the group consisting of hydrogen, acyl, optionally substituted lower alkyl, optionally substituted lower alkenyl, optionally substituted lower alkynyl, optionally substituted cycloalkyl, optionally substituted heterocycle, optionally substituted heterocycloalkyl, optionally substituted aryl, optionally substituted aralkyl, optionally substituted heteroaryl, and optionally substituted heteroaralkyl,

provided, however, that R¹ and R², or R⁴ and R⁵, or R⁹ and R¹⁰, or R² and R³ can combine to form an optionally substituted heterocycle;

Y and Z are independently selected from the group consisting of O and S;

R⁸ is selected from the group consisting of, hydroxy, alkoxy, thioalkoxy, optionally substituted amine, optionally substituted lower alkyl, optionally substituted lower alkenyl, optionally substituted lower alkynyl, optionally substituted cycloalkyl, optionally substituted heterocycloalkyl, optionally substituted aryl, optionally substituted aralkyl, optionally substituted heteroaryl, optionally substituted heteroaralkyl, and optionally substituted heterocycle; and

R¹¹ is selected from the group consisting of hydroxy, alkoxy, thioalkoxy, optionally substituted lower alkyl, optionally substituted lower alkenyl, optionally substituted lower alkynyl, optionally substituted cycloalkyl, optionally substituted heterocycloalkyl, optionally substituted aryl, optionally substituted aralkyl, optionally substituted heteroaryl, and optionally substituted heteroaralkyl;

R⁶ is

Z¹, Z², Z³, and Z⁴ are independently selected from the group consisting of —O—, —S—, —CR^6a—, —CR^6b—, —CR^6c—, and —NR^6d—, wherein:

at least one of Z¹, Z², Z³, and Z⁴ is a heteroatom; and

Z¹, Z², Z³, and Z⁴ are selected to produce a stable compound;

R^6a, R^6b, and R^6c are independently selected from the group consisting of hydrogen, halo hydroxy, alkoxy, alkylthio, alkylsulfinyl, alkylsulfonyl, acyloxy, optionally substituted aryl, amino, amido, amidino, urea optionally substituted with alkyl, aryl, heteroaryl or heterocyclyl groups, aminosulfonyl optionally N-mono- or N,N-di-substituted with alkyl, aryl or heteroaryl groups, alkylsulfonylamino, arylsulfonylamino, heteroarylsulfonylamino, alkylcarbonylamino, arylcarbonylamino, heteroarylcarbonylamino, carboxyl, optionally substituted heterocycle, optionally substituted hetaryl, nitro, cyano, thiol, sulfonamido, optionally substituted alkyl, optionally substituted alkenyl, and optionally substituted alkynyl, attached at any available point to produce a stable compound; or

R^6a, R^6b, and R^6c can, in combination with the five-membered ring comprising Z¹, Z², Z³, and Z⁴, combine to form an optionally substituted fused heterocyclic ring system; and

R^6d is optionally present, and when present is selected from the group consisting of hydrogen, optionally substituted lower alkyl, optionally substituted aryl, optionally substituted heterocycle, optionally substituted heteroaryl, acyl, sulfonyl, amido, thioamido, and sulfonamido;

provided, however, that

when R⁶ is thiophen-2-yl, then R¹ and R² are not selected from the group consisting of phenyl, lower alkyl, and lower alkenyl;

when R⁶ is furan-2-yl, then R¹ and R² are not selected from the group consisting of optionally substituted phenyl and optionally substituted phenylalkyl; and

when R¹ or R² is furan-2-yl-methylene or furan-2-yl-ethylene, then R⁶ is not optionally substituted phenyl.