Patent ID: 8008496

Claim:
A compound represented by the following formula (1) or a pharmaceutically acceptable salt thereof: wherein R 1 represents a hydrogen atom or a lower alkyl group; R 2 represents a hydrogen atom or a lower alkyl group; R 3 and R 4 may be the same or different and represent a hydrogen atom or a lower alkyl group; R 5 represents a hydrogen atom or a lower alkyl group; R 6 represents a halogen atom, a lower alkyl group, a hydroxy group, a lower alkoxy group, a nitro group or a cyano group; X represents —C(O)—, —C(O)NR 8 —, —S(O)— or —S(O) 2 —; R 7 and/or R 8 may be the same or different and represent a hydrogen atom, a lower alkyl group which may have a substituent, a lower alkenyl group which may have a substituent, a lower alkynyl group which may have a substituent, a lower cycloalkyl group which may have a substituent, an aryl group which may have a substituent, a heterocyclic group which may have a substituent, a lower alkoxy group which may have a substituent, a lower alkenyloxy group which may have a substituent, a lower alkynyloxy group which may have a substituent, a lower cycloalkyloxy group which may have a substituent, an aryloxy group which may have a substituent or a heterocyclic oxy group which may have a subustituent; Y represents a lower alkylene group; Z represents a chalcogen atom; p represents 0, 1, 2 or 3, in the case where p is 2 or 3, each R 6 may be the same or different.