| 摘要 |
A compound represented by the formula (I): wherein Ris lower alkyl, cycloalkyl or aromatic hydrocarbon ring, each of which is optionally substituted with one or more substituents; Ris hydrogen atom, halogen atom, lower alkyl, halo(lower)alkyl or lower alkoxy; and Ris (1) a group represented by the formula: wherein Ris lower alkyl, etc.; (2) a group represented by the formula: wherein Ris lower alkyl, etc.; (3) a group represented by the formula: wherein Ris lower alkyl, etc.; or (4) a group selected from halogen atom, carboxy, hydroxy and lower alkoxy, or a salt thereof.
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