Patent ID: 8653126

Claim:
A compound represented by the general formula (I): or an isotope thereof or a pharmaceutically acceptable salt thereof wherein, R 1 is a methyl group which may be substituted with the same or different 1 to 3 halogen atoms, R 2 is a C1-C6 alkyl group which may be substituted with the same or different 1 to 3 halogen atoms, a C3-C6 cycloalkyl group, a C1-C6 alkoxy C1-C6 alkyl group, a C3-C6 cycloalkoxy C1-C6 alkyl group, a C2-C6 alkenyl group, a di(C1-C6 alkyl group)amino group, a furanylmethyl group, an oxetanyl group, an acetyloxymethyl group, a propylcarbonyloxymethyl group, a tert-butylcarbonyloxymethyl group, a phenylcarbonyloxymethyl group, a hydroxymethyl group, a dimethylaminosulfonyl group, a diethylaminosulfonyl group, a pyrrolidinesulfonyl group, a piperidinesulfonyl group or a morpholinesulfonyl group, R 3 is a hydrogen atom, an acetyl group, a benzoyl group or a pivaloyl group, and R 4 is a hydrogen atom or a halogen atom.