The present invention provides a compound represented by the formula (1) or a pharmacologically acceptable salt thereof, or a hydrate thereof (provided that a compound in which all of R4a, R4b, and R4c are hydrogen atoms is excluded.):
[wherein R1 represents a hydrogen atom, R2 represents a hydrogen atom, R3 represents the formula:
wherein R4a, R4b, and R4c are the same as or different from each other and each represents a hydrogen atom, a C
1-6
alkyl group or a C
1-6
alkoxy group, etc.]