Patent ID: 6987114

Claim:
A compound of formula (I) or a pharmaceutically acceptable salt thereof: wherein R represents cyclopropyl; cyclobutyl, 1- or 2-naphthyl; 9-anthracenyl; 2-anthraquinonyl; 2-, 3- or 4-quinolinyl; oxiranyl; 1-benzotriazolyl; 2-benzoxazolyl; furanyl substituted with C 1 –C 4 alkoxycarbonyl; C 1 –C 4 alkylcarbonyl; or benzoyl, R 1 represents halogen or C 1 –C 4 alkyl, R 2 and R 3 represent independently hydrogen or C 1 –C 4 alkyl, X represents oxygen atom, and Y represents oxygen atom, sulfur atom or carbonyl.