prov:value
| - wherein R1 is a hydrogen atom, a lower alkyl group, an aryl group which may have a substituent, or a heterocyclic group, and R2 to R5, each of which may be the same or different, are individually a hydrogen atom, a halogen atom, a lower alkyl group, an alkoxy group, an acyl group, a nitro group, a cyano group, an amino group, a dialkylamino group, a diarylamino group, a vinyl group which may have
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