Disclosed is a compound represented by Formula (I) or a pharmaceutically acceptable salt thereof:wherein R1 is1: a C3-8 cycloalkyl C1-4 alkyl group,2: a C7-14 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) C1-4 alkyl, which is optionally substituted with 1 to 3 fluorine atoms,(c) C1-4 alkoxy, which is optionally substituted with 1 to 3 fluorine atoms, and(d) C1-4 alkylcarbonyl, which is optionally substituted with C1-4 alkoxy,3: a five- to ten-membered heteroaryl-C1-4 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) C1-4 alkyl, or4: a C6-10 aryl C2-6 alkenyl group； andR2 is a cyano group or a nitro group.
