prov:value
| - wherein R1, R2, R3, and R4 is a functional group selected from the group including hydrogen, an alkyl group, a thiol group, an aromatic group, a carboxyl group, a carbonyl group, an ether linkage, an ester group, an amine group, an allophanamide, a glycolyl group, a carbonic acid, or any combination thereof.
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