prov:value
| - A process of claim 4 wherein R1, R2, R5, R6 and R10 in the formula (I-a) are each a hydrogen atom, amino group, hydroxyl group, alkyl group, alkoxyl group, amido group, sulfonamido group, carbamoyl group, or ureido group, and at least one of them is not a hydrogen atom, and R10 is a hydrogen atom, alkyl group, alkoxyl group, amido group, sulfonamido group, alkoxycarbonylamino group or ureido group
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