Toluene dioxygenase mediated oxidation of halogen-substituted benzoate esters

A series of ortho-, meta-, and para- halogen-substituted methyl benzoate esters was subjected to enzymatic dihydroxylation via the whole-cell fermentation with E. coli JM109 (pDTG601A). Only ortho-substituted benzoates were metabolized. Methyl 2-fluorobenzoate yielded one diol regioselectively whereas methyl 2-chloro-, methyl 2-bromo- and methyl 2-iodobenzoates each yielded a mixture of regioisomers. Absolute stereochemistry was determined for all new metabolites. Computational analysis of these results and a possible rationale for the regioselectivity of the enzymatic dihydroxylation is advanced.