Patent ID: 8569327

Claim:
A compound represented by formula (1) or a salt thereof: wherein: R 1 represents a hydrogen atom, a lower alkyl group, a hydroxyl group, a lower alkyloxy group, or a halogen atom; R 2 represents a hydrogen atom, a lower alkyl group, a halogen atom, a lower alkylcarbonyloxy group optionally having a substituent, a heterocyclic carbonyloxy group, a lower alkyloxycarbonyloxy group, a lower alkyl-substituted aminocarbonyloxy group, an amino group optionally having a substituent, a lower alkyl-substituted amino group optionally having a substituent, a heterocyclic group, a lower alkyloxycarbonylamino group optionally having a substituent, a lower alkylcarbonylamino group, a formamide group, or a hydroxy lower alkyl group; R 3 represents a hydrogen atom, a lower alkyl group, a hydroxyl group, or a halogen atom; R 4 represents a hydrogen atom or a lower alkyloxy group; R 5 represents a lower alkyloxy group, a halogen atom, a hydroxyl group, or a methylenedioxy group formed together with R 6 or an isopropylidenedioxy group formed together with R 6 ; R 6 represents a lower alkyloxy group, a methylenedioxy group formed together with R 5 or an isopropylidenedioxy group formed together with R 5 ; R 7 represents a hydrogen atom or a lower alkyl group; and R 8 represents a hydrogen atom, a hydroxyl group, an amino group, a lower alkylcarbonyloxy group, or a halogen atom.