prov:value
| - R3 : alkyl of 1 to 4 carbon atoms, e.g. methyl, ethyl, n-propyl, isopropyl, n-butyl and isobutyl, substituted alkyl of 1 to 4 carbon atoms, e.g. methoxymethyl, ??-methylthioethyl, benzyloxymethyl, carbethoxymethyl and carbethoxyethyl, benzyl, which may be unsubstituted, or monosubstituted or disubstituted by alkoxy or acyloxy (where alkyl is in each case of 1 to 4 carbon atoms), or by benzyloxy, o
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