Toluene Dioxygenase-Catalyzed Synthesis and Reactions of <i>cis</i>-Diol Metabolites Derived from 2- and 3‑Methoxyphenols

Using toluene dioxygenase as biocatalyst, enantiopure <i>cis</i>-dihydrodiol and <i>cis</i>-tetrahydrodiol metabolites, isolated as their ketone tautomers, were obtained from <i>meta</i> and <i>ortho</i> methoxyphenols. Although these isomeric phenol substrates are structurally similar, the major bioproducts from each of these biotransformations were found at different oxidation levels. The relatively stable cyclohexenone <i>cis</i>-diol metabolite from <i>meta</i> methoxyphenol was isolated, while the corresponding metabolite from <i>ortho</i> methoxyphenol was rapidly bioreduced to a cyclohexanone <i>cis</i>-diol. The chemistry of the 3-methoxycyclohexenone <i>cis</i>-diol product was investigated and elimination, aromatization, hydrogenation, regioselective <i>O</i>-exchange, Stork–Danheiser transposition and <i>O</i>-methylation reactions were observed. An offshoot of this technology provided a two-step chemoenzymatic synthesis, from <i>meta</i> methoxyphenol, of a recently reported chiral fungal metabolite; this synthesis also established the previously unassigned absolute configuration