A compound of formula (I) in which: R1 is selected from the group consisting of hydrogen, carboxy, alkyl, halogenated C1-4 alkyl, substituted C1-4 hydroxy alkyl, aryl, aralkyl, heteroaryl, -C (O) -alkyl, -C (O) - (halogenated C1-4 alkyl), -C (O) O-C1-4 alkyl, -C (O) O-aryl, -C 1-4 alkyl- and S (O) 0 -2-C1-4 alkyl； wherein the aryl or the heteroaryl, either alone or as part of a substituent group, are optionally substituted with one or more substituents independently selected from the group consisting of halogen, hydroxy, C1-4 alkyl, C1-4 alkoxy, alkyl Halogenated C1-4, halogenated C1-4 alkoxy, cyano, nitro, amino, C1-4 alkylamino, -NRc-C (O) -C 1-4 alkyl (O) O-C1-4 alkyl and NRc-C (O ) - (halogenated C1-4 alkyl)； wherein each Rc is hydrogen or C1-4 alkyl； R2 is selected from the group consisting of C1-4 alkyl and halogenated C1-4 alkyl； X is selected from the linking group consisting of -C (O) -, -C (S) -, -C (O) -C (O) - and -S (O) 1-2-； Y is selected from the linking group consisting of -C (O) -, -C (O) -C (O) -, - S (O) 1-2- or an N atom； Z is selected from the group consisting of C, N or O； provided that when Z is O, R1 is absent； A is O or S； R3 is absent or is selected from the group consisting of hydrogen, halogen, C1-4 alkyl, halogenated C1-4 alkyl, cyano, nitro, amino, C1-4 alkylamino, di (C1-4 alkyl) amino, -O- C1-4 alkyl, -S (O) 0-2-C1-4 alkyl, NRB-C (O) -C1-4 alkyl, benzyl, -O-phenyl, -C (O) -phenyl and -S (O ) 0-2-phenyl； where RB is hydrogen or C1-4 alkyl； R4 is absent or selected from the group consisting of hydrogen, halogen, C1-4 alkyl, halogenated C1-4 alkyl, cyano, nitro, amino, C1-4 alkylamino, di (C1-4 alkyl) amino, -O- C1-4 alkyl, -S (O) 0-2-C1-4 alkyl, NRB-C (O) -C1-4 alkyl, benzyl, -O-phenyl, -C (O) -phenyl and -S (O ) 0-2-phenyl； wherein RB is selected from hydrogen and C1-4 alkyl； or a pharmaceutically acceptable salt thereof, in which "aryl" refers to unsubstituted carbocyclic aromatic groups； and "heteroaryl" refers to any five or six mem
