prov:value
| - Suitably, at most only three, and preferably at most only two, of R2 to R5 are other than hydrogen and each is independently selected from hydrogen, halo, hydroxy, nitro, C1-3 alkyl optionally substituted by hydroxy or C1-2 alkoxy, C1-3 alkoxy, amino optionally substituted by one or two methyl or ethyl groups, or a group S(O)n R23 wherein n is 0, 1 or 2 and R23 is a C1-4 alkyl group or an amino gr
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