The potential role of cis-dihydrodiol intermediates in bacterial aromatic hydroxylation and the NIH Shift

Specifically deuteriated samples of toluene, anisole, chlorobenzene, alpha,alpha,alpha-trifluoromethylbenzene, naphthalene and quinoline have been synthesised and used as substrates for dioxygenase-catalysed asymmetric dihydroxylation studies to yield the corresponding cis-dihydrodiols as major bioproducts. Phenols were also detected as minor metabolites in some cases. Dehydration of the deuterium-labelled cis-dihydrodiol metabolites, under thermal conditions, in all cases, resulted in phenol formation accompanied by the NIH Shift. A comparison of NIH Shift results, obtained when phenols are produced by aromatisation of chemically synthesised deuteriated arene cis- and trans-dihydrodiols (dehydration) and arene oxides (isomerisation), suggests that this phenomenon may be associated with both monooxygenase- and dioxygenase-catalysed aromatic hydroxylations.