Disclosed is a compound represented by Formula (I) or a pharmaceutically acceptable salt thereof: wherein R 1 is 1: a C 3-8 cycloalkyl C 1-4 alkyl group, 2: a C 7-14 aralkyl group, in which the aryl moiety thereof is optionally substituted with the same or different 1 to 3 groups selected from the group consisting of: (a) halogen, (b) C 1-4 alkyl, which is optionally substituted with 1 to 3 fluorine atoms, (c) C 1-4 alkoxy, which is optionally substituted with 1 to 3 fluorine atoms, and (d) C 1-4 alkylcarbonyl, which is optionally substituted with C 1-4 alkoxy, 3: a five- to ten-membered heteroaryl-C 1-4 alkyl group, in which the heteroaryl moiety thereof is optionally substituted with the same or different 1 to 3 groups selected from the group consisting of: (a) halogen, and (b) C 1-4 alkyl, or 4: a C 6-10 aryl C 2-6 alkenyl group； and R 2 is a cyano group or a nitro group.
