prov:value
| - wherein R1 represents a quarternary carbon atom, a metyne group or a methylene group which may contain a heteroatom such as N, S, O or P, Y contains one or more saturated and/or unsaturated bonds which define, together with R1, a ring fused to the benzene ring of the above formula, R2 and R3 are independently selected from alkyl, alkenyl, alkoxy, aryl which may contain one or more substituents, ar
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