prov:value
| - wherein R1 is a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, R2 is a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, an aryl group, an alkylaryl group, an arylalkyl group or an alkoxy group, R3 and R4 are each independently a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, an aryl group that can be substituted, ???COOR5, ???OCOR6, a cyano group or a halogen ato
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