prov:value
| - In a further preferred embodiment, R1 is selected from C1-6alkyl, for example methyl, ethyl, n-propyl, isopropyl, 1,1-dimethylpropyl, 1-ethyl-1-methyl-propyl, n-butyl, isobutyl, 1,1-dimethylbutyl, 1,3-dimethylbutyl, 3,3-dimethylbutyl, 2-pentyl or 1-methylpentyl, optionally substituted by up to three groups selected from C1-6alkoxy, in particular C1-4alkoxy groups such methoxy or t-butoxy, halogen,
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