A compound of the formula (I): ** Formula ** wherein one of the two links is a single bond and the other is a double bond； X1 is O and X2 is CR2； each of Y and Z, independently, is O, S, or NRb, wherein Rb is H, alkyl, alkenyl, alkynyl, aryl, heteroaryl, cycloalkyl, cycloalkenyl, heterocycloalkyl, heterocycloalkenyl, cyano, or NO2； each of R1 and R2, independently, is H, alkyl, alkenyl, alkynyl, aryl, heteroaryl, cycloalkyl, cycloalkenyl, heterocycloalkyl, heterocycloalkenyl, halo, cyano, nitro, ORc, OC (O) Rc, C (O) Rc, C (O) ORc, C (O) NRcRd, NRcRd, NHC (O) Rc, NHC (O) NRcRd, NHC (S) Rc, NHC (O) ORc, SO3Rc, or SO2NRcRd, in which each of Rc and Rd, independently, is H, alkyl, alkenyl, alkynyl, aryl, heteroaryl, cycloalkyl, cycloalkenyl, heterocycloalkyl, or heterocycloalkenyl； each of R3 and R4, independently, is H, halo, nitro, cyano, amino, hydroxy, alkoxy, aryloxy, alkyl, alkenyl, alkynyl, cycloalkyl, cycloalkenyl, heterocycloalkyl, aryl, or heteroaryl； A is arylene or heteroarylene； B is O, S or NRe, wherein Re is H, alkyl, alkenyl, or alkynyl； C is O, S, alkylene, or NRf, wherein Rf is H, alkyl, alkenyl, or alkynyl； or B and C, together with the carbon atom to which they are attached, are heterocycloalkyl or heterocycloalkenyl； D is H, alkyl, alkenyl, alkynyl, aryl, heteroaryl, cycloalkyl, cycloalkenyl, heterocycloalkyl, or heterocycloalkenyl； or C and D together are heterocycloalkyl, heterocycloalkenyl, aryl, or heteroaryl； and n is 1, 2, 3, or 4. wherein each of alkyl, alkenyl, alkynyl, aryl, heteroaryl, cycloalkyl, cycloalkenyl, heterocycloalkyl, and heterocycloalkenyl optionally is substituted with C2-C10 alkenyl, C2-C10 alkynyl, C3 cycloalkyl - C20, C3-C20 cycloalkenyl, C1-C20 heterocycloalkyl, C1-C20 heterocycloalkenyl, C1-C10 alkoxy, aryl, aryloxy, heteroaryl, heteroaryloxy, amino, C1-C10 alkylamino, arylamino, hydroxy, halo, oxo (O>； =) , thioxo (S>； =), thio, silyl, C1-C10 alkylthio, arylthio, C1-C10 alkylsulfonyl, arylsulfonyl, aminothioacyl, ami
