Patent ID: 8273761

Claim:
A compound represented by the formula: wherein R 1 is C 1-6 alkyl, C 3-6 cycloalkyl, C 6-10 aryl or mono-C 1-6 alkylamino, R 2 is a hydrogen atom or C 1-6 alkyl, R 3 is a hydrogen atom or C 1-6 alkyl, m is 0, 1 or 2, the tricycle consisting of ring A, ring B and ring C is a ring represented by the formula wherein ring A optionally has one C 1-6 alkyl, ring B is unsubstituted, and ring C optionally has one substituent at the carbon atom selected from the group consisting of (1) C 1-6 alkyl optionally having 1 to 3 halogen atoms, (2) C 3-6 cycloalkyl and (3) C 6-10 aryl optionally having 1 to 3 halogen atoms, and is a single bond or a double bond, or a salt thereof.