| prov:value
| - or a group of the formula ##STR15## where R9 and R10, which can be identical or different, are a hydrogen atom, a halogen atom or an alkoxy group having 1 to 3 carbon atoms, and, when n is 1, a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, R2 is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, R3 is a hydrogen atom, R4 is a hydrogen atom, a straight-chain or branched-ch
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