prov:value
| - R4, R5, R6, and R7, same or different, are independently hydrogen, alkyl, arylalkyl, alkylaryl, halogen, including bromo and chloro, acetoxy, alkylacetoxy, arylacetoxy, carboxy, alkylcarboxy, hydroxy, or alkoxyhydroxy, preferably, R4, R5, R6, and R7, same or different, are hydrogen or C1-C8 alkyl.
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