prov:value
| - ein R1, R2, R3, R4 and R8 are the same or different and each is a hydrogen atom or a lower alkyl group, R2 and R3 in combination may form, together with the carbon atoms to which they are bonded, a cyclopentane ring or a cyclohexane ring, R5, R6 and R7 are the same or different and each is a hydrogen atom, a halogen atom, a lower alkyl group optionally substituted by halogen atom(s) or a lower alk
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