Syntheses and estrogenic activity of 4-nonylphenol isomers

Eight branched 4-nonylphenol (NP) isomers, which were identified from commercially available NP reagent, 4-(1-ethyl-1,4-dimethylpentyl)phenol (NP-C), 4-(1,1-dimethyl-3-ethylpentyl)phenol (NP-D), 4-(1,3-dimethyl-1-ethylpentyl)phenol (NP-E(G)), diastereomeric mixture), 4-(1,1,4-trimethylhexyl)phenol (NP-F), 4-(1-methyl-1-n-propylpentyl)phenol (NP-H), 4-(1,1-dimethyl-2-ethylpentyl)phenol (NP-I), 4-(1,1,2-trimethylhexyl)phenol (NP-M), and 4-(1-ethyl-1-methylhexyl)phenol (NP-N), were synthesized by two different synthetic methods starting from 4-benzyloxyacetophenone or phenol. The chemical structures of the synthesized compounds were confirmed by MS and NMR spectroscopy. The estrogenic activities of these synthetic NP isomers were tested and exhibited different activities on the recombinant yeast screen system. NP-I was found to exhibit three times greater estrogenic activity than the commercial NP mixture.