Patent ID: 8916549

Claim:
A compound represented by the formula (I) wherein R 1 and R 2 are the same or different and each is a hydrogen atom, or a C 1-3 alkyl group optionally substituted by a halogen atom(s) (at least one of R 1 and R 2 is a C 1-3 alkyl group optionally substituted by halogen atom(s)), or R 1 and R 2 form, together with the adjacent carbon atom, (a) a C 3-4 cycloalkyl group optionally substituted by halogen atom(s), (b) a phenyl group substituted by substituent(s) selected from a halogen atom and a C 1-3 alkoxy group, or (c) a furyl group; and R 3 and R 4 are the same or different and each is a hydrogen atom or a C 1-3 alkyl group, or a salt thereof.