Disclosed is a compound represented by the general formula (I) below, or a pharmaceutically acceptable salt or ester thereof. (In the formula, R and R may be the same or different and represent a hydrogen atom, a lower alkyl group, a cycloalkyl group or the like； R and R may be the same or different and represent a hydrogen atom, a lower alkyl group, an NRR, a phenyl group, a lower alkyl group substituted with a phenyl group, a 4- or 7-membered aliphatic heterocyclic group, a lower alkyl group substituted with a 4- or 7-membered aliphatic heterocyclic group, a 5- or 6-membered aromatic heterocyclic group, a lower alkyl group substituted with a 5- or 6-membered aromatic heterocyclic group or the like； and R represents a hydrogen atom, a cyano group, a halogen atom or a lower alkyl group.)
