(2) In (1), a compound wherein R1 is a methyl group, or a pharmacologically acceptable salt thereof; (3) in (1) or (2), a compound wherein R2 is a methyl group, or a pharmacologically acceptable salt thereof; (4) in (1) to (3), a compound wherein R3 is a phenyl group substituted with 1 to 3 groups selected from the group consisting of a lower alkyl group, a cycloalkyl group and a lower alkoxy grou